Glossary of Automotive Terms – I

Letter I – Dictionary of Automotive Terms

Short form for injection indicating that the engine is fuel-injected, e.g., GTi, EFi, 1.6i, SSEi
I2R Loss
Power loss due to the current (I) flow through the resistance (R) of a conductor.
Abbreviation for Intake Air
Abbreviation for Idle air control valve
Abbreviation for Idle Air Control Valve
I & C systems
Abbreviation for instrumentation and control systems
Abbreviation for Integral alternator/Regulator
Abbreviation for Inlet Air Solenoid (Ford)
Abbreviation for International Auto Sound Challenge Association.
Abbreviation for Intake Air Temperature. The same as a MAT
A steel beam that is shaped like the letter I when you look at the cross section
I-beam suspension
A suspension which uses an I-beam. The wheels on opposite sides of the vehicle are linked by a solid member, usually an I-beam but sometimes a tube. This minimizes the pieces needed for the suspension, but weighs slightly more, so is seldom used on high-performance vehicles. It was most common on older car front suspensions, but is now most commonly used on the rear of front-wheel-drive vehicles.

I-beam axle
  1. Abbreviation for Integral Back Pressure
  2. Abbreviation for Initial Boiling Point. In a standard laboratory distillation, the temperature on the distillation thermometer at the moment the first drop of distillate falls from the condenser.
  1. Abbreviation for Integrated Circuit
  2. Abbreviation for Ignition Control


Abbreviation for Interstate Commerce Commission. The U.S. federal body formerly charged with enforcing Acts of Congress affecting interstate commerce. The ICC was decommissioned in 1993.
ICC Bumper
A bumper typically made out of 3′ to 4′ steel channel stock, usually about 75% of the width of the trailer, suspended half the distance from the trailer floor to the pavement with a strong enough bracing to meet federal regulations governing underride guards.
  1. Abbreviation for in-car entertainment
  2. Abbreviation for internal combustion engine
Ice cream cabinet
Commercial refrigerator which operates at approximately -18°C; used for storage of ice cream.
Ice Cube Maker
Abbreviation for Internal Combustion Engine Institute, Inc.
Ice Maker
Ice melting equivalent
(IME-ice melting effect) Amount of heat absorbed by melting ice at 0°C is 144 Btu per pound of ice or 288,000 Btu per ton.
IC engine
Abbreviation for internal combustion engine


Ice scraper
A small plastic hand-held implement for scraping frost and ice away from windshields and windows. A CD disc does the job even better because it always keeps its edge. Some ice scrapers are located at the end of a brush stick.
A condition where ice forms at the edge of the carburetor Throttle plate/butterfly. It restricts the flow of the fuel-air mixture when the Throttle butterfly is at or near the idle position. It causes the engine to stall. Ice forms because of rapid Vaporization of the fuel which lowers the temperature of the mixture and causes the moisture in the air to freeze. It can occur when the temperature is between -2 to 13°C and the relative humidity is above 64%. It usually occurs after the engine is started and before it has reached operating temperature.

Icing switch
A device that cuts off the compressor when the evaporator temperature drops below a predetermined level
Abbreviation for Ignition Control Module— Whether DIS, EDIS, or TFI – module which controls ignition spark
Abbreviation for Injection Control Pressure
  1. Abbreviation for Idle Control Solenoid (GM)
  2. Abbreviation for Integral collector storage
  3. Abbreviation for Internal Collector Storage
  4. Abbreviation for Incident Command System –for Emergency Management
Abbreviation for Ignition Control Unit
Abbreviation for Fisher’s no-draft individually controlled ventilation — vent windows found on 1933 Cadillacs.
Abbreviation for inside diameter.
Ideal air-fuel ratio
Identical part
Identification color
  1. A particular color for a specific amperage of fuse.
  2. A color scheme for wiring
Identification number
Identification plate
Provides information such as manufacturer, part number, and specifications. Frequently mounted on the outside housing of motors and compressors.
Abbreviation for integrated direct ignition system
Idiot box
Trucker slang for a T.V. set as in ‘When I get home I’m gonna buy me a new idiot box.’
Idiot light
Idiot lights
A colloquial term for the indicator lights on the dashboard which are illuminated when the vehicle is experiencing some problem such as a lack of oil, overheating, failed brakes, low fuel, etc. The alternative is to install gauges which indicate the level of fluids and temperature. A combination of both gauges and lights is ideal.
Abbreviation for Idle Position Switch
  1. The Engine speed when the vehicle is not moving. The engine’s slowest practical speed.
  2. A running engine without added throttle pressure while the vehicle is stationary.
Idle air bleed screw
A screw found on some carburetors which allows air to enter the carburetor when the throttle is closed, so that the vehicle can idle. It also prevents the formation of deposits in the throttle area. The adjustment of this screw is part of a basic Tune-up.

Idle-air Bypass
Idle air control valve (IAC)
  1. On a fuel injection vehicle, a valve that allows air to bypass the throttle plate(s), increasing idle speed. The valve is operated by an electric solenoid or motor. The vehicle computer controls the amount of opening to regulate idle speed for varying conditions such as cold string and air conditioner compressor load
  2. An electronically controlled device that controls idle speed on fuel injected vehicles by controlling bypass air.
Idle air jet
A hole in a fixed-jet carburetor through which air is drawn into the idle system
Idle air stabilization valve
Electronically controlled valve used to maintain idle speed at a predetermined level
Idle cam
Idle capacity
The component of operable capacity that is not in operation and not under active repair, but capable of being placed in operation within 30 days; and capacity not in operation but under active repair that can be completed within 90 days.
Idle channel restriction
Used on carbureted vehicle. Does the same thing as the idle feed restriction, but is located in the idle passage just below the idle air bleed instead of the bottom of the idle tube. In the primary idle channel, the amount of fuel emitted by the idle discharge port is adjustable because there is a screw with a tapered tip extending into the port. On the secondary side, the idle discharge port uses a fixed idle channel restriction with no adjustment
Idle circuit
At idle and low speeds, the carburetor system supplies enough fuel to the engine to keep it running. When the vehicle gets up to speed (usually about 24 kph or 15 mph) the idle circuit kicks out of operation so that fuel is supplied by the main metering system. Also called the low-speed circuit.
Idle Compensator
Idle discharge hole
Used on carbureted vehicle. The hole through which the idle mixture enters the airstream flowing past the throttle plate. Also called curb-idle port
Idle feed restriction
Used on carbureted vehicle. A metering orifice that controls the amount of fuel that can enter the idle tube. Also called idle orifice or idle jet.
Idle jet
A carburetor jet within the idle system which supplies a constant amount of fuel for the formation of the idle mixture
Idle limiter
Any device that limits the maximum richness of the idle air/fuel mixture in the carburetor. Also aids in preventing overly rich idle adjustments. Limiters take either of the two following forms And external plastic cap or a internal-needle type located in the idle passages of the carburetor
Idle limiter cap
An external plastic cap on the head of the idle mixture adjustment screw to maintain preset emissions levels and prevent unauthorized tampering
Idle mixture
The mixture of air and fuel (usually about 14:1) being fed to the cylinders when the throttle plate is closed. Idle mixture is controlled by the pilot circuit in the carburetor or the computer in an electronic fuel injection system.
Idle mixture adjustment screw
Idle mixture screw
A tapered screw located on the outside of the carburetor which controls the proportion of the fuel-air mixture. It is now illegal to adjust these if limiter caps are present. If you turn the screw clockwise, the mixture will be leaner while turning it the other way results in a richer mixture.
Idle orifice
The idle restriction tube or idle jet
Idle power
The system rate of doing work when only the minimum work rate is employed by the system.
  1. A gearwheel between a driving and a driven gear in a gear train which may serve to reverse the original direction of rotation of the driven wheel.
  2. A free-turning pulley or wheel which serves to maintain tension in a belt drive.
Idler arm
In a parallel relay-type Steering linkage, it is one of the connecting levers. The steering Gearbox is attached to a pitman arm which converts rotary motion to lateral motion. The pitman arm connects to a transverse centerlink which connects to the idler arm attached to the frame side rail on the opposite side of the vehicle. The ends of the centerlink connect to two adjustable Tie rods that transmit the lateral movement of the centerlink to the steering arms at each steering knuckle.
Idle regulation electrovalve
located in the throttle flap bypass circuit, it compensates for engine rpm drop when the air conditioning compressor or other engine loads are operated.
Idler gear
A gear that is placed between two other gears to reverse the direction of rotation of the output gear.

Idler pulley
  1. The Pulley in a rear derailleur that stays farthest from the freewheelCogs and functions to keep tension on the chain of a bicycle.
  2. A small pulley located about half way from the front to back of a long chain such as found on a tandem bicycle.
  3. A spring-loaded pulley designed to maintain the tension of the timing belt or a cam chain.
Idle screw
Idle solenoid
Idle speed
  1. This is the speed of the engine with the following conditions: the transmission is in neutral (or park in automatic transmissions), the engine is fully warmed up, the choke butterfly is fully open, and there is no extra accessories in operation (i.e., air conditioner, radio, lights). Also called idling speed.
  2. The crankshaft rotational speed in an engine with a closed throttle plate.
Idle speed actuator
An electronically-controlled air bypass around the throttle. Also called Idle-speed stabilizer or a Constant idle system
Idle speed adjustment
The alteration of the engine idle speed.
Idle speed control (ISC)
  1. Maintains the idle speed of the engine at a minimum level. There are currently two types of computer controlled idle speed control DC motor ISC and air bypass ISC
  2. An electronically controlled device that maintains idle speed on vehicles by controlling throttle position at idle.
Idle speed control motor
(ISC) and ECM controlled motor that extends or retracts a plunger that contacts the throttle level, which regulates the position of the throttle valve to compensate for an additional load, such as the air conditioner, power steering pump, etc. On the engine. Although it regulates idle speed, it is not used to adjust the curb idle speed. ISC motors are commonly used on carbureted and throttle body injected (TBI) vehicles
Idle speed screw
A screw located at the bottom of the carburetor on the outside which keeps the throttle from closing completely when the vehicle is idling and thus controls the Idle speed. This is adjusted as part of a basic Tune-up.
Idle speed stabilizer
A device which ensures steady engine rpm at idle speed. An electronically-controlled air bypass around the throttle. Also called Idle speed actuator or a Constant idle system
Idle stabilizer valve
A device used to control the amount of air for engine operation at idle. It consists of a rotary valve connected to an armature. During normal operation, a duty cycle is applied to the armature by the ECU. This causes the valve to rotate in a direction opposite to spring tension. Lengthening or shortening the electrical pulses of the duty cycle causes the opening for the bypass air to become larger or smaller, resulting in the idle speed rising or falling accordingly. When no current is applied to the rotary valve, it is pressed by spring pressure against a stop and maintains a specific air gap. This will allow the engine to idle, if the stabilizer fails.
Idle stop solenoid
A small cylinder located on the outside of the carburetor on some cars. It prevents the vehicle from continuing to idle after the Ignition switch has been shut off (i.e., Dieseling). The position of the striker rod in the cylinder can be adjusted in a Tune-up to the correct Specifications.
Idle stop valve
A solenoid-operated valve which cuts off fuel in the idle system of a carburetor and so stops the engine from running-on when the ignition is switched off
Idle system
At idle speed, the throttle valve is closed to such an extent that the airflow underneath the plunger no longer forms a sufficient vacuum; the fuel is then supplied via an auxiliary system, the idle system, which consists of the idle jet, the idle air jet, and the mixture control screw
Idle time
The time when a system is capable of but not producing power; startup time
Idle tracking switch
(ITS) used on CFI vehicle to inform the EEC if the throttle is in contact with the DC motor
Idle transfer port
A port drilled into the carburetor body slightly above the idle port to allow extra fuel/air emulsion into the airstream during the transition period when the throttle plate is opening from its idle (closed) position to a larger (cruising) opening angle. Also called idle transfer slot
Idle transfer slot
A port drilled into the carburetor body slightly above the idle port to allow extra fuel/air emulsion into the airstream during the transition period when the throttle plate is opening from its idle (closed) position to a larger (cruising) opening angle. Also called idle transfer port
Idle vacuum valve
(IVV) used in conjunction with other vacuum controls to dump air injection system air during extended periods of idle, to protect the catalyst
The action of an engine as it turns over at low speed with minimum throttle.

Idling circuit
The passages, jets, etc. in a fixed-jet carburetor which provide idling mixture to the carburetor barrel
Idling drag
The forward motion of a vehicle with automatic transmission, with engine at idle and selector lever in position D (Drive). Also called creep
Idling speed
  1. Abbreviation for Ignition Diagnostic Monitor
  2. Abbreviation for Injector Driver Module


International Energy Agency

  1. Abbreviation for Industrial Fasteners Institute.
  2. Abbreviation for Indirect Fuel Injection
  1. Abbreviation for Independent front suspension.
  2. Abbreviation for Inertia Fuel Switch
Abbreviation for ignition
Abbreviation for Ignition
Abbreviation for Ignition Advance
Abbreviation for Ignition Ground
To set fire to; to catch fire
  1. A Bridge igniter with detonator in an air bag system.
  2. An electronic control unit or module used by Japanese automotive and ignition manufacturers
  3. A device that uses electrical energy to ignite gas at a pilot burner or main burner.
A process which initiates the combustion of the compressed air/fuel mixture in the combustion chamber. In a spark-ignition engine, the mixture is ignited by an electric spark; in a diesel engine, the self-igniting mixture must be preheated by glow plugs when a cold start is performed.

Ignition Activation Period
The period of time between energizing the main gas valve and deactivation of the ignition means prior to the lockout time.
Ignition advance
The extent to which the ignition spark is made to occur earlier. The opposite is Ignition retard.

Ignition amplifier
A device used to increase the electrical signal in an electronic ignition system
Ignition angle
The angle, measured in degrees crankshaft, by which the ignition is advanced.
Ignition cable
A general term to designate the high-voltage cables of the ignition system, from the ignition coil to the distributor and from the distributor to the spark plugs. Also called ignition leads
Ignition capacitor
The electrical part which interrupts the primary current with low loss and suppresses most of the arcing between the contact breaker points in conventional coil ignitions
Ignition circuits
Ignition coil

Ignition coilIgnition coil

A step-up pulse transformer which is a part of the ignition system. It receives a small amount of electrical voltage from the battery and steps up the low primary voltage and amplifies it into a big jolt of voltage of about 20,000 volts, and sends it to the spark plugs via the distributor. It is made of two windings and a core of iron. The primary coil has about 200 turns of relatively heavy wire. The secondary windings may have as much as 22,000 windings of fine wire. As electricity travels through the primary winding, it produces a magnetic field in the coil. When the points open, the magnetic field collapses and the movement of the magnetic field induces current in the secondary windings of the coil. The voltage is stepped up in proportion to the ratio of secondary to primary turns and the distributor directs this high voltage to the spark plug. Also called just coil.

Ignition coil resistor
A ballast resistor
Ignition Control
Ignition control unit
A general control unit of electronic ignition systems, usually with current and dwell angle control, driver and output stage, in some cases with electronic spark timing functions. Compare Electronic control unit
Ignition delay
The time lag between ignition triggering and the production of a spark
Ignition device
A device for igniting fuel at a burner. It may be a pilot or an igniter.

Ignition disabler
A standard feature of car alarm systems
Ignition distributor
Ignition engine
Ignition file
A tool for filing ignition points and other small objects. Also called Contact file, Magneto file, Points file, or Point file
Ignition gauge
A blade or wire-type feeler gauge used to check gaps on ignition systems, such as air gaps between permanent magnet and trigger wheel on electric ignitions
Ignition generating coil
Coil in a flywheel magneto to provide primary ignition current.
Ignition key
A key which is inserted into an ignition lock located in the passenger compartment (usually on the steering column or on the instrument panel) and is used to switch on the ignition
Ignition lag
The time lag between fuel injection and combustion in a diesel engine
Ignition-latched soft code
A type of trouble code that causes the ECU to disengage the ABS until the ignition is shut off and turned back on; if the problem has gone away, the ABS will be reactivated and the warning lamp turned out when the key is turned back on
Ignition lead
A general term to designate the high-voltage cables of the ignition system, from the ignition coil to the distributor and from the distributor to the spark plugs. Also called ignition cable
Ignition map
An electronic map stored in the electronic control unit of ignitions with electronic spark timing and containing the most favorable ignition angle/ignition point for every operating point of the engine. Spark timing is optimized on the basis of fuel type and consumption, torque, exhaust gas, knock limit, engine temperature, etc.
Ignition module
A transistorized component in an electronic ignition that triggers the ignition coil to fire high voltage. It replaced the breaker points on older cars.

Ignition oscilloscope
An oscilloscope used especially for ignition tune-ups; usually integrated in an engine tester
Ignition pattern
A display of the waveforms in the primary or secondary circuit of an ignition system in the firing order of the engine; optionally parade or display pattern and stacked or raster pattern.

Ignition Pickup
Ignition point
  1. The moment of spark firing.
  2. breaker points.
Ignition point file
Ignition points
Ignition primary
The low-voltage part of the ignition circuit, such as part of the ignition coil wiring, the pickup, electronic ignition module, and ECM. Compare Ignition secondary
Ignition primary circuit
The low voltage portion of the ignition system.
Ignition retard
Ignition which occurs after top dead center

Ignition secondary
The high-voltage part of the ignition circuit, such as part of the ignition coil wiring, spark plugs, spark plug wires, distributor cap, and rotor. Compare Ignition primary
Ignition secondary circuit
The high voltage portion of the ignition system.
Ignition setting
Ignition switch
A control device that is generally operated with a key that closes and opens an electrical current to connect and disconnects the ignition system from the battery so that the engine can be started and stopped as desired. The key should not be removable when the engine is running. It usually has various positions which, besides starting the engine, allow the user to operate the accessories without engaging the engine or to check the Bulbs in the warning lights on the dashboard.
Ignition system
The system that provides the electrical current or spark to ignite the air-fuel mixture in the combustion chambers. It includes the battery or magneto which sends electricity to the ignition coil if the Ignition switch is on. The coil amplifies the electrical charge and sends it to the distributor where it goes through the points and is modified by the condenser. The distributor sends it along the high tension lines (spark plug wires) to the spark plugs where it ignites the air-fuel mixture.

Ignition temperature
Ignition Time
Ignition timing
  1. It is important that the spark coming from the spark plugs ignites the air-fuel mixture at the correct moment determined by the manufacturer of the engine. Often this is a few degrees before top dead center (BTDC). Suppose the specs indicate that it should be set at 5 degrees BTDC, but in actuality it is set at 6 degrees. In that case, the timing is advanced. If it were set at 4 degrees, the timing is retarded. Incorrect ignition timing may result in poor performance and excessive fuel consumption.
  2. The relationship between the time a spark plug is fired and the position of the piston in terms of degrees of crankshaft rotation.
Ignition toolkit
A set of small tools usually comprising 8 small open-ended wrenches (sizes 3/16 – 7/16 in), a feeler gauge, a small screwdriver and a points file
Ignition transformer
  1. A unit that transforms the primary voltage resulting from the capacitor discharge to the required high voltage
  2. Transformer designed to provide a high-voltage current. Used in many heating systems to ignite fuel; provides a spark gap.
Ignition transistor
A transistor that switches the primary current of a transistorized ignition system
Ignition voltage
The voltage at which the spark jumps across the electrodes; 30,000 volts are quite common today.

Ignition wrench
A small, open-ended wrench about 3 inches (75mm) long. It had two jaw openings set at different angles to the handle, e.g., 15° at one end and 60° or 75° at the other. (The British term is electrical spanner). The available jaw sizes were the following

15° 75° Length
13/64′ 15/64′ 3′
7/32′ 1/4′ 3′
1/4′ 7/32′ 3′
9/32′ 5/16′ 3-1/2′
5/16′ 9/32′ 3-1/2′
Ignitor, ceramic
Electric ignition system used in a water glycol solution, forced-air furnace. Electrically heated to create ignition of the gas-air mixture in the combustion chamber.
Ignitor Tube
I head
An Overhead valve engine.

An Overhead valve engine.

I head engine
An engine where both intake and exhaust valves are placed directly over the piston. The cam is located in the block and the valves are activated by pushrods and Rocker arms. Also called overhead-valve engine or valve-in-head engine.
I-head engine

I-head engineI-head engine

An engine where both intake and exhaust valves are placed directly over the piston. The cam is located in the block and the valves are activated by pushrods and Rocker arms. Compare F-head engine where one valve is in the head and the other in the block; and the L-head engine where both valves are in the block and none in the head. Also called overhead-valve engine or valve-in-head engine.

Abbreviation for Indicated horsepower. Indicated horsepower developed by an engine and a measure of pressure of explosion within cylinder express in pounds per square inch
Abbreviation for International Harmonized Research Activities.
Abbreviation for Insurance Information Center of Canada.
Abbreviation for the US Insurance Institute for Highway Safety
Abbreviation for Idle Load Compensator
Abbreviation for inherently low-emission vehicle
Lit up
Illuminated entry system
An additional courtesy lighting system which illuminates the door entry area when the door is ajar; consists usually of lights in the lower door panels and footwells
Illumination control
A switch which dims the interior instrument panel lights
Unlike reflective strips illuminite technology makes the entire garment reflective. The illumiNITE process embeds millions of microscopic satellite dishes into the weave of the fabric. These dishes act like mirrors to reflect back to the original light source. Because the dishes are embedded into the fabric, the garment remains machine washable without losing any of its reflective properties.
Abbreviation for US based International Lubricants Standardization and Approval Committee is controlled by the API. It includes the major the US vehicle manufacturers, the US engine manufacturers association and Japanese manufacturers who assemble vehicles in the US. The standards work in addition to the API SH, SJ, and SM standards for engine oils and are effectively the fuel economy version of the those oil specifications. The ILSAC GF-1 standard indicates the oil meets both API SH and the Energy Conserving II (EC-II) requirements. It was created in 1990 and upgraded in 1992 and became the minimum requirement for oil used in American and Japanese automobiles. An EC-II oil provides a 2.7% fuel economy improvement over reference used in a laboratory test engine. ILSAC GF-1 specifications apply to multigrade oils that have a 0, 5 and 10 W rating and 20, 30, 40 or 50 summer rating. ILSAC GF-2 replaced GF-1 in 1996. The oil must meet both API SJ and EC-II requirements. The GF-2 standards requires 0W-30, 0W-40, 5W-20, 5W-30, 5W-40, 5W-50, 10W-30, 10W-40 and 10W-50 motor oils to meet stringent requirements for phosphorus content, low temperature operation, high temperature deposits and foam control. GF-3 an oil must meet both API SL and the EC-II requirements. The GF-3 standard has more stringent parameters regarding long-term effects of the oil on the vehicle emission system, improved fuel economy and improved volatility, deposit control and viscosity performance. The standard also requires less additive degradation and reduced oil consumption rates over the service life of the oil. The GF-4 standard was introduced in 2004 and increases the compliance parameters over GF-3 by a significant margin.
Abbreviation for Inspection and Maintenance Programs
Abbreviation for Inspection and Maintenance
Abbreviation for Idle Mixture Adjuster
IMA sensor
idle mixture adjuster sensor
Abbreviation for International Mountain Bicycling Association which is an organization dedicated to protect mountain bike trails
A lack of balance due to uneven weight distribution. Improper wheel balance due to uneven weight distribution on the tire and wheel assembly is one of the most common causes of vibration. When one side of the tire and wheel assembly is heavier than the other, centrifugal forces try to throw the heavy area outwards as the wheel turns.

Abbreviation for improved combustion
Abbreviation for Indicated mean effective pressure
Abbreviation for Institute of the Motor Industry, a British organization for managers in the motor industry
To dip into or submerge in a liquid
Immersion treatment
A vehicle that is unable to move
To make immobile
A device that makes something immobile (such as a Denver boot)
To remove small particles of iron or grit from the surface of stainless steel by pickling in an acid solution.
A sudden, hard, physical contact.

Impact absorber
An impact-damping element located between the bumper and bumper mounting to keep impact energy from being transferred into the car body
Impact adhesive
A contact glue that provides adhesion when two coated surfaces are pressed together
Impact air bag
Impact bar
Impact break
A rupture to a tire resulting from the shock of striking a chuck-hole, rock, curb, etc. and not caused by cutting.
Impact cushion
Some child seats secure the child by an impact cushion in addition to the seat belt or straps
Impact damage
Damage that has been caused to the wall of a tire by contact with a curb or deep pothole, etc.
Impact driver
Impact dummy
Impact intrusion beam
Impact pipe
A simplified version of an Impact absorber
Impact resistance test
A determination of the resistance to breakage by flexural shock of plastics, as indicated by the energy extracted from standardized pendulum-type hammers, mounted in standard machines, in breaking standard specimens with one pendulum swing
Something that is stiffened (to a certain degree) to resist the force of a collision
Impact screwdriver
A tool which features a mechanism that converts the impact from a hammer into a powerful torque for loosening (or tightening) threaded fasteners. Also called impact driver.
Impact sensor
An open switch that is designed to close when an crash occurs that is severe enough to warrant air bag deployment.

Impact socket
A heavy duty socket for use with air or electric power impact tools. Impact sockets are designed to stand up to the extreme stress of these tools and can be used in combination with special impact accessories such as extensions, universal joints, and adapters. These accessories are also designed to withstand the stress of air or electric power impact tools
Impact standard
Impact Statement
Impact strength
The ability of a material to resist shock loading strain
Impact stress
The force per unit area imposed on a material by an abruptly applied force
Impact swivel ball universal joint
The swivel ball type universal joint is the most common type for use with impact sockets
Impact test
An experiment to determine the amount of energy absorbed in hitting an object at high velocity.

Impact wrench
A pneumatic or electric tool for use with impact sockets
Impaired driver
A driver whose judgment is impaired by alcohol or drugs.
Chevrolet Impala BooksClick image for books on
Chevrolet Impala

A model of large car produced by the Chevrolet division of General Motorsfrom 1959-2008.

Impedance (Z)
  1. Opposition in an electrical circuit to the flow of an alternating current that is similar to the electrical resistance to a direct current.
  2. The vectorial sum of both resistance and reactance in an electric motor; total opposition to current flow, measured in ohms. Z is the impedance symbol
  3. Any device that introduces electrical opposition in the form of resistance, reactance, or both.
Impedance Voltmeter
  1. A rotating member of a centrifugal pump which is equipped with vanes to convert mechanical energy into fluid energy. A rotor or wheel with blades or Vanes used in pumps to drive and circulate fluid.


  2. A fluid coupling or torque converter — the driving member connected to the crankshaft via drive plate and converter cover which generates the fluid flow inside the converter. The driving Torus in the Fluid coupling or Torque converter of an automatic transmission.
  3. Finned wheel that produces pressure and flow when spun in the enclosed housing of an oil or water pump.
Impeller eye
The inlet area of an impeller in a pump
Impeller pump
A centrifugal and side-channel pump
ImperialClick image for books on

A vehicle brand of which the 1955-56 models are milestone cars.

Imperial gallon
A quantity of 4.546 litres. Also called UK gallon. It is 20% larger than a US gallon
Imperial phaeton
Imperial sedan
A drop or sliding glass partition between the Driver’s compartment and the Tonneau is the distinguishing feature between this type and the sedan, which it resembles in all other respects.

Not capable of leaking fluid
Not allowing gas to pass through
An organization that typically operates at arms length or under contractual agreement with manufacturers to bring into the country products made in another country.

Import Measures Act
Import nameplate
Vehicles sold by manufacturers primarily located outside North America whether assembled Overseas or in North America.
Improved recovery
Extraction of crude oil or natural gas by any method other than those that rely primarily on natural reservoir pressure, gas lift, or a system of pumps.
Undesirable foreign material(s) in a pure substance or mixture.
Abbreviation for Intake Manifold Runner Control (formerly IAC Intake Air Control) Controls variable inlet systems (VIS)
  1. Abbreviation for Ignition Module Signal
  2. Abbreviation for Inferred Mileage Sensor (Ford)
Abbreviation for International Motorsports Association.
Abbreviation for Intake Manifold Timing
The ability of a precision insert bearing to allow a small abrasive particle to imbed itself in the bearing material so it will not scratch the surface of the journal.
Located near the vehicle center rather than at the outside. Opposite of Outboard
Inboard brake
Inboard brakes
Most cars have the brakes associated with the wheel. drum brakes, for instance, are located in the wheel hub itself. disc brakes are found attached to the wheel. However, inboard brakes are not located within the wheel. Instead, they are found attached to the Differential housing or axle shaft. Thus they are generally located only on the rear of the vehicle. Some racing cars (i.e., Formula 1) have them on the front as well. Inboard brakes mean a reduction in Unsprung weight and usually better cooling.
Inboard motor
An engine which is located within a boat rather than being attached to the back (outboard motor).
Inboard Profile
A drawing of the longitudinal section at centerline of ship.
Inboard starter
A Bendix starter
In Bond
  1. Storage of goods in custody of government/bonded warehouse or carrier from whom goods can be taken only upon payment of taxes/duties to appropriate government agency.
  2. Import shipments moving into or through the United States that have not cleared U.S. Customs at the border and, therefore, travel under a U.S. Customs (Treasury) bond.
Incandescent lamp
A glass enclosure in which light is produced when a tungsten filament is electrically heated so that it glows. Much of the energy is converted into heat; therefore, this class of lamp is a relatively inefficient source of light. Included in this category are the familiar screw-in light bulbs, as well as somewhat more efficient lamps, such as tungsten halogen lamps, reflector or r-lamps, parabolic aluminized reflector (PAR) lamps, and ellipsoidal reflector (ER) lamps.
Incandescent bulb
light bulbs, including regular or energy-efficient light bulbs: An incandescent bulb is a type of electric light in which light is produced by a filament heated by electric current. The most common example is the type you find in most table and floor lamps. In commercial buildings, incandescent lights are used for display lights in retail stores, hotels and motels. This includes the very small, high-intensity track lights used to display merchandise or provide spot illumination in restaurants. Energy efficient light bulbs, known as watt-savers, use less energy than a standard incandescent bulb. Long-life bulbs, bulbs that last longer than standard incandescent but produce considerably less light, are not considered energy-efficient bulbs. This category also includes halogen lamps. Halogen lamps are a special type of incandescent lamp containing halogen gas to produce a brighter, whiter light than standard incandescent. Halogen lamps come in three styles: bulbs, models with reflectors, and infrared models with reflectors. Halogen lamps are especially suited to recessed or canned fixtures, track lights, and outdoor lights.
In-car entertainment
(ICE) A car audio system, typically consisting of a radio/cassette player and perhaps a CD player. The term also includes a CB radio, TV, VCR, DVD available on some models (e.g., limousines and sleepers on large trucks)
In-car sensor
A dual bimetal strip that samples passenger compartment air and controls a vacuum modulator. The vacuum modulator controls the heating or air conditioner blend door to maintain a constant temperature in the passenger compartment
Inches of mercury
(in-Hg) a unit of measurement which designates the relative amount of vacuum present in a closed system
Incident light
The amount of light reaching an object.
Incipient crack
A crack which has just started to form
Abbreviation for includes, as in price incl. tax.
A set angle.

  1. A slope
  2. To slope
Inclined engine
An in-line engine in which the cylinders are inclined to the vertical. Also called a sloper or slant six (e.g., Chrysler’s 6-cylinder engine
Inclined plane
A Wedge used to raise a load more easily. The load moves, not the wedge.
Included angle
The sum of the Camber and Kingpin inclination (or steering axis inclination) angles. This angle is designed into the steering knuckle and must remain constant.
Included Angle of Thread
The angle between the flanks or the thread measured in an axial plane.
Incomplete thread
  1. A thread with incomplete thread profile
  2. On straight threads, that portion at the end having roots not fully formed by the lead or chamfer on threading tools
Increased shank
A shank diameter greater than thread diameter
Increasing adapter
An adapter whose male end for the socket is bigger than the female end for the drive handle. The opposite is a Reducing adapter
Increasing-radius corner
A turn where the arc becomes less sharp as you go through the curve
In-dash gauge
A gauge mounted in the instrument panel
A concentrated panel damage or specific dent that may be caused when a car hits a relatively small obstacle, i.e., the hitch ball of another car
Indentation hardness
The resistance of a metal (or plastic) surface to indentation when subjected to pressure by a hard pointed or rounded tool
Independent ABS
An ABS in which the ABS hydraulic components are connected to, but separate from, the normal brake hydraulic system and power booster. Sometimes called a Non-integral system or Non-integrated system
Independent front suspension
(IFS) A Suspension system where the two front wheels are sprung independently from each other. It has the advantage over a Beam axle suspension because it allows the engine to be positioned further forward and lower between the wheels. In this way there is more room for the passengers, the position of the hood is lower, the vehicle has a lower Center of gravity, and the Unsprung weight is reduced. When the front wheels are not independently sprung, there is some Caster wobble and Shimmy that make it difficult to hold on to the steering wheel.

Independent lessor
Independent lessors are usually individual businesses that can provide for the lease of virtually any make or model of vehicle. Independent lessors, like dealers, can write custom leases, including those with different conditions and special mileage considerations.
Independent rear suspension
(IRS) A Suspension system where the two rear wheels are sprung independently from each other. It has the advantage over a Beam axle suspension because the Unsprung weight is reduced, the ride and handling over rough roads are improved, and a larger trunk with a lower floor can be placed between the wheels.

Independent repair shop
A small service outlet offering specialized repair services. They usually do not sell gasoline.
Independent suspension
A Suspension system that allows each wheel to move up and down without undue influence on the other wheels. Thus independent suspension on the rear wheels means that if only the right rear wheel hits a bump, the left rear wheel is not affected by it. Generally it is more expensive to manufacture independent suspension.
Independent Trucker
Index improver
Index marks
Marks used to properly align a distributor for engine timing.
Index shifter
Index shifters
bicycle levers that click into distinct positions that correspond to certain freewheel Cogs and don’t require fine-tuning after each shift.
IndianClick image for books on

A motorcycle manufacturer

Indicated horsepower
(IHP) A measure of the power developed by the burning fuel within the cylinders. The theoretical power of an engine calculated from the MEP in the cylinders rather than at the shaft. IHP includes Bhp plus the power lost to friction, and pumping needed for the induction of the fuel and air charge into the engine and the expulsion of combustion gases
Indicated mean effective pressure
  1. (IMEP) The average pressure within an engine cylinder during a working cycle, calculated from an indicator diagram
  2. The pressure at the top of the piston.
Indicated pressure
  1. An instrument which reveals the condition of a particular component.
  2. A British term for a signal light.
  3. An instrument for recording engine cylinder pressure.
Indicator diagram
A cylinder pressure chart, plotted against the working cycle of a piston or engine
Indicator lamp
Indicator light
A light on the instrument panel that lights up to show the operation of something, such as the illuminated arrow that indicates the direction in which a vehicle is about to turn, the high beam indicator, battery charge indicator, oil pressure light, cruise control light, etc.

Indicator Reading
Indicator warning light
Indirect Damage
A type of damage not caused by immediate impact but by the spread of the impact force into other areas of the body, e.g., bulging or dents at the rear of the front fender and the leading edge of the door in the case of direct accident damage to the front edge of the front fender. The opposite is Direct damage
Indirect drive transmission
A transmission where power is transferred from the clutch to the input shaft, and to the output shaft.
Indirect ignition system
A system in which the ignition means functions to ignite the main burner gas and the igniter sensing device proves the ability of the ignition means to ignite the main burner gas.
Indirect injection

  1. A type of fuel injection in which the air-fuel mixture does not go into the main combustion chamber but into some kind of prechamber; injection pressures are lower than with Direct injection and Ignition lag is short
  2. In diesel engines with in-direct injection the fuel is injected to an auxiliary pre-chamber. Combustion starts in the prechamber and propagates to the cylinder.
Indirect injection engine
A British term for a pre-combustion engine, i.e., a diesel engine using Indirect injection
Indirect internal reforming
The reformer section is separated, but adjacent to, the fuel cell anode. This structure takes advantage of the close coupled thermal benefit from the exothermic reaction of the fuel cell to support the endothermic reforming reaction.
A metallic element with the symbol In and atomic number of 49. It is used in the manufacture of transistors and as a bonding material for acoustic Transducers.
Individual valve Main Burner
A valve that controls the fuel supply to an individual main burner.
To cause or to bring about
Induce a voltage
To produce a voltage by electromagnetic induction
Induced-Draft burner
A burner which depends on the draft induced by a fan beyond the gas utilization equipment for its proper operation.
Induced magnetism
Ability of a magnetic field to produce magnetism in a metal.
In a turbocharger, the section of the compressor wheel that draws air or air/fuel mixture into the compressor
  1. (L) The characteristic of a coil or wire to cause the current to lag the voltage in time phase. Inductance is measured in henrys (H)
  2. That property of an electric circuit or of two neighboring circuits whereby an electromotive force is generated (by the process of electromagnetic induction) in one circuit by a change of current in itself or in the other.
  1. The imparting of electricity into one object, not connected, to another by the influence of magnetic fields. Found in automobiles in coils and Solenoids.
  2. A means of transferring electrical energy in the form of a magnetic field. Principle used in the ignition coil to increase voltage
  3. The intake of air and fuel through the carburetor, inlet manifold, and inlet ports into the combustion chamber.
  4. Production of current flow by forming a magnetic field and moving it through a conductor.
Induction coil


Induction hardening
Method of heating cast iron (e.g., valve seats) to approx 927°C which hardens it to a depth of 0.05 to 0.08 inches
Induction manifold
Induction motor
  1. An ac motor which operates on principle of rotating magnetic field. Rotor has no electrical connection, but receives electrical energy by transformer action from field windings.
  2. An alternating-current motor in which a primary winding on one member (usually the stator) is connected to the power source, and a secondary winding on the other member (usually the rotor), carries only current induced by the magnetic field fo the primary. The magnetic fields react against each other to produce a torque. One of the simplest, reliable, and cheapest motors made.
Induction noise
The sound caused by the intake of air by an engine at full throttle
Induction period
The time during the charge changing process of the engine that allows for the intake of the fresh charge into the cylinder while the inlet control, i.e., the valve or port, remains open
Induction pipe
The duct, typically an alloy manifold, between the throttle and cylinder head; the absolute pressure in the induction pipe, the so-called intake vacuum, is indicative of engine load and is used to control many engine-related functions
Induction pod
The port in the cylinder wall of a two-stroke engine which is used for the admission of the fresh charge into the cylinder
Induction stroke
A British term for the intake stroke, i.e., the phase of the 4-stroke cycle during which the intake valve is open and the piston descends from TDC to BDC, drawing air (in a diesel engine) or an air/fuel mixture (in a spark ignition engine) into the cylinder
Induction system
  1. The system that brings the fuel-air mixture to the cylinders in a spark ignition engine. It includes the carburetor or fuel injection system, Air cleaner, intake manifold, Intake ports, and intake valves.
  2. Air intake system used to cool the car.
Induction system intake configuration
Induction timing
A joystick used on power wheelchairs
Inductive ignition system
An ignition system where the primary energy is stored in an inductor or an ignition coil
Inductive pick-up
Inductive pulse pick-up
Inductive reactance
Electromagnetic induction in a circuit creates a counter or reverse (counter) emf (voltage) as the original current changes. It opposes the flow of alternating current.
Inductive winding
Industrial Classification
Industrial Classification System
Industrial tire
A heavy duty tire for use on forklifts, lowbed trailers, etc.
Industrial solid
A non-pneumatic tire (either entirely rubber or a regular tire with a solid rubber core to replace the tube), used most often on forklifts where the possibility of a flat tire is a constant problem.
Industrie Normen
  1. Something that lacks a chemical action
  2. A substance that exhibits no chemical activity, or does so only under extreme conditions
  3. The property of the separators used between the plates of a battery
Inert arc welding
A family of arc welding processes in the fusion welding category. The welding pool is surrounded by a layer of inert shielding gas to keep oxygen from the weld; TIG welding is a typical inert arc welding process and is mainly used for repair work
Implies that a tank is filled with an inert gas.
Inert Gas
A gas such as carbon dioxide or nitrogen that is used to make an oxygen deficient atmosphere. Inerted tanks are useful for preserving cargo integrity and reducing the explosive potential of cargo tanks.
Inert gas-arc welding
Surrounding the arc with a gas which does not react with the electrode and base metal and keeps the atmosphere away from the arc.
Inert gas system
A system of filling the space above the cargo oil in tankers with carbon dioxide from the boiler exhaust so as to prevent explosion.
Inert Gas Welding
That force which tends to keep a stationary object from being moved, and tends to keep a moving object in motion. Some effort is needed to get the object moving if it is stopped, and to stop an object if it is moving.

Inertia drive
A Bendix drive which has a heavy piston moving along the shaft under the momentum of its own weight or inertia when the shaft turns inside it
Inertia fuel cut-off switch
Inertial load
A load (flywheel, fan, or the like) which tends to cause the electric motor shaft to continue to rotate after the power has been removed
Inertia pinion
A Pinion used in an Inertia drive
Inertia reel
Generally the seat and shoulder belts are loose so that the drive and passenger can have the freedom to move forward to adjusting the instruments on the dash, etc. However, when the vehicle decelerates quickly, as in a crash or panic stop situation, the occupants need to be restrained by the belts. The belts are locked by the inertia reel as it senses the rapid change of deceleration.
Inertia reel seat belt
A 3-point seat belt with an automatic retractor reel. This type of seat belt allows the wearer to move while the vehicle is stationary or in steady motion but locks to restrain the wearer on sudden deceleration or impact
Inertia switch
A gravity actuated safety device which de-energizes the ignition, inhibits fuel pump operation, and activates the central locking system to open all door locks and close both the luggage compartment and fuel filler locks should the vehicle be subjected to heavy impact force.
Infant safety seat


Passage of outside air into building through doors, cracks around windows, etc.

Infinitely variable transmission
(IVT or CVT) Most transmissions, whether manual or automatic have a fixed number of forward gears (from 2 to 10 or more). Belt driven vehicles (like snowmobiles) have an infinite number of positions of engagement. The infinitely variable transmission is sensitive to the changes in the throttle position and adjusts the Gear ratio accordingly. In this way, the most efficient Gear ratio is selected thus improving fuel economy. Also called continuously variable transmission.
InfinitiClick image for books on

The luxury automobile division of Nissan Motor Co., Ltd. established in 1989. Includes

  • FX35 (2003-07)
  • FX45 (2003-07)
  • G20 (1991-2002)
  • G35 (2003-08)
  • I30 (1996-2001)
  • I35 (2002-04)
  • J30 (1993-97)
  • M30 (1990-92)
  • M35 (2006-08)
  • M45 (2003-08)
  • Q45 (1990-2006)
  • QX4 (1997-2003)
  • QX56 (2004-07)
An ohmmeter reading which indicates an open circuit in which no current will flow
Capable of being easily ignited and of burning quickly
Inflatable air-bag system
Inflatable restraint
To fill with air.

Inflation control seam
A system of inflation control seams on advanced air bags to control the inflation speed and inflation characteristics. Also called tear seam, whose negative connotations are perhaps inappropriate in a safety-related context
Inflation pressure
Inflation table
Inflator unit
An assembly beneath the folded air bag, consisting of a combustion chamber with a bridge igniter, a detonator, and a priming charge surrounded by the solid propellant, and a metal filter. A signal from the trigger unit causes the bridge igniter to fire the detonator, which in turn fires the priming charge and then the solid propellant. The nitrogen thus generated flows through a metal filter and reaches the air hag cleaned and cooled
Information centers
Visual displays which alert driver to certain vehicle conditions
Information System
Infrared analyzer
An instrument used to measure unburned hydrocarbons and CO discharged from a vehicle exhaust pipe.

Infrared lamp
Electrical device which emits infrared rays; invisible rays just beyond red in the visible spectrum.
Infrared radiant drier
An infrared lamp which accelerates the drying of large areas of fresh paint
Infrared rays
Heat rays which emanate from both the arc and the welding flame.
Infrared remote control
(IR) the control of an operation by means of an infrared beam transmitted to a receiver (e.g., garage door, central locking, car alarm system, etc.)
Steel (and other metals) formerly in a molten state, transferred to an rectangular mold to solidify.
Entry, as in ‘sealant is used to prevent the ingress of moisture’.
Inherently Low-Emission Vehicle

  1. Any vehicle that is certified to meet transitional low-emission vehicle standards established by the CARB and does not emit any evaporative emissions.
  2. A vehicle meeting EPA’s CFV ILEV standards. Tailpipe standards may be HC LEV with ULEV NOx, ULEV, or ZEV and includes the additional requirement that evaporative emissions be 2 grams per test over the full test procedure and 5 grams per test without the use of any auxiliary emission control devices. ILEVs will be dedicated AFVs in most cases. Dual-fuel vehicles will be considered ILEVs only if both fuels meet the standard. (Very low-volatility gasoline may also meet the standard.) ILEVs are exempt from certain transportation control measures, including HOV lane restrictions. This standard is voluntary and need not be adopted by states.
To hinder or to prevent
  1. A substance which prevents chemical reaction such as corrosion or oxidation.
  2. A substance added to oil, water, gas, etc., to prevent action such as foaming, rusting, etc. The opposite is catalyst.
Inhibitor switch
Inhibitor valve
In-House Damage
Damage to product that occurred while in the warehouse (i.e., water leak, dropped product, etc.).
Initial enrichment
Average enrichment for a fresh fuel assembly as specified and ordered in fuel cycle planning. This average should include axial blankets and axially and radially zoned enrichments.
Initial stopping speed
Speed of a motor vehicle at the start of brake application
Initial Storage
Warehouse storage charge for the month when product is received; it is typically billed when product is received.
Abbreviation for Injector Valve which injects fuel into inlet, duration times commanded by the PCM. INJ 1 to INJ 10 refers to Fuel Injectors 1 to 10
To introduce a fluid (into something) under pressure
Injected engine
Injection burner
Two types:

  1. Bunsen Type: A burner employing the energy of a jet of gas to inject air for combustion into the burner and mix it with the gas.
  2. Atmospheric Type: A burner in which the air at atmospheric pressure is injected into the burner by a jet of gas.
Injection engine
Injection fuel
In Bosch CIS, the pressure of the fuel in the lines between the differential-pressure valves and the injectors. Also called Injection pressure
Injection lag
The time interval (expressed in crankshaft degrees) between the nominal start of injection pump delivery and the actual start of injection at the nozzle
Injection manifold
Produced by an Injection molding machine or process
Injection molding
A method for the fabrication of thermoplastic materials. The viscous resin is squirted, by means of a plunger, out of a heated cylinder into a water-chilled mold, where it is cooled before removal. This method is also used with thermosetting molding powders.

Injection moulding
British term for Injection molding
Injection molding machine
A machine used to produce preformed plastic body panels
Injection period
  1. The length of time for which fuel is sprayed into the intake ports or combustion chamber during fuel injection. It is controlled by the electronic control unit. The injection period depends mainly on engine speed and the amount of induced air and is normally between approx. l.5 and 9 milliseconds
  2. The time, measured in degrees of crankshaft rotation, between the beginning and end of injection. On engines with hydromechanical injection systems, it is controlled by the opening and closing of ports in the injector body or by the action of a plunger forcing fuel out of a cup. On electronic injection systems, it is determined directly or indirectly by the action of a solenoid valve.
Injection pressure
In Bosch CIS, the pressure of the fuel in the lines between the differential-pressure valves and the injectors. Also called Injection fuel
Injection pump
A pump which receives fuel from the fuel tank (often through the fuel-feed pump in the case of diesel engines) and delivers it under pressure to the injectors.

Injection pump governor
Device which controls fuel deliver to limit the minimum and maximum engine speeds, as well as intermediate throttle positions
Injector opening pressure
The point at which injection pump fuel pressure overcomes nozzle valve-spring resistance, or combustion chamber pressure, so that fuel is injected into the pre-combustion chamber
Injection reaction
Injection system
  1. A pump and lines that deliver oil to a two-stroke engine.
  2. A fuel system which meters gasoline into an engine’s intake ports.
Injection valve


A solenoid or pressure-operated fuel delivery valve (used in a fuel injection system) that squirts or injects a measured amount of gasoline into the intake manifold in the vicinity of the intake valve. In a diesel engine fuel is injected directly into the cylinder. In a CIS, the injectors atomize the continuous flow of fuel injected under pressure into the intake ports of the engine; a valve in the injector nozzle stops the flow of fuel when fuel pressure drops below a certain point; in a CIS, the quantity of fuel is regulated by the fuel distributor’s metering unit; in other fuel injection systems, the fuel system delivers a constant supply of fuel at a constant pressure to the injector, and an electronic sensing and control system produces electrical current pulses of appropriate duration to hold open the injector solenoid valves; as fuel pressure is held constant, varying the pulse duration increases or decreases the amount of fuel passed through the injectors.

Injector nozzle
The tip of the injector, either of multi-hole design for direct injection or pintle design for indirect injection.

Partial pavement removal and replacement, normally used to eliminate ruts in roadway surface.
An opening in the face of, and under, a curb allowing water to enter the drainage system.

Inlet cam
The cam responsible for the actuation of the inlet valve in DOHC engines
Inlet camshaft
The cam responsible for the actuation of the inlet valve in DOHC engines
Inlet line
A pipe or hose on the intake side of a component, through which a fluid is supplied by gravity from a reservoir or tank located at a higher level; e.g., from coolant expansion tank to radiator, or from brake fluid reservoir to master brake cylinder
Inlet manifold
British term for intake manifold describing the component which guides the intake air to the cylinder head intake ports; usually an aluminum casting or a GRP molding, with one intake opening and as many outlets as there are cylinders in the engine
Inlet manifold heater
Inlet over exhaust
Valve layout used on some early machines in which the exhaust valve was mounted to the side of the engine and the mechanically operated inlet valve was positioned above the exhaust
Inlet over exhaust engine
(IOE engine) A British term for intake over exhaust engine describing an engine design used on early cars. Also called F-head engine The intake and exhaust valves are arranged vertically in a lateral chamber of the combustion chamber and face one another; the side valve (usually the exhaust) is actuated directly by the camshaft, which usually rotates in the cylinder block; the overhead valve (usually the intake) is located in the cylinder head and actuated via a pushrod and rocker arm
Inlet pipe
Inlet port
A British term for Intake port

Inlet sock
A coarse fuel filter in an older fuel tank, designed to remove only very large dirt particles; it can last the life of the car. The sock is made of saran, so water won’t enter until the sock is entirely engulfed in water.
Inlet stroke
A British term for Intake stroke
Inlet System
Inlet tract
A British term for Intake tract
Inlet valve
A valve that opens to allow the fuel/air mixture to enter the combustion chamber. A British term for intake valve

Inlet valve closes
(IVC) A British term for Intake valve closes
Inlet valve opens
(IVO) A British term for Intake valve opens
Engine layout in which the cylinders are arranged in a row, and in-line with the wheels of the machine
Inline compressor
Two-cylinder compressor with the pistons arranged side-by-side, like a York or Tecumseh
Inline cylinders
Cylinders positioned in a row or side by side. Unlike Horizontally opposed engine, Flat engine, V-type engine, W-type engine, or X-type engine.
Inline engine
An engine in which the cylinders occur in a single row with the crankshaft running along the bottom.

In-line engine
An engine in which all the cylinders (usually three or more) are arranged in a straight row (either vertically or slanted). The pistons drive a common crankshaft. Also called a straight engine.
Inline filter
A small fuel or oil filter that is installed in a section of line or hose. See Inline fuel filter.
In-line five-cylinder engine

In-line five-cylinder engineIn-line five-cylinder engine

An engine type that was first introduced by Mercedes-Benz in 1974. Its advantage is that it produces more power than a four cylinder but takes up less space than an in-line six.

In-line four-cylinder engine

In-line four-cylinder engineIn-line four-cylinder engine

An engine type often found in lightweight economy and sports cars. It is short enough to be placed sideways in some front-wheel-drive models. Most fours vibrate noticeably, especially at low engine speeds.

Inline filter
Inline fuel filter
Inline fuel filter
In-line fuel filter
A fuel filter which is placed within the fuel pipes or hoses coming from the fuel tank or fuel pump. It is made of pleated paper or nylon mesh and encased in a transparent plastic or glass housing. To install it, a segment of the fuel line is cut and removed. The filter is inserted to replace the removed segment of the fuel line.
Inline fuel heater
A heater which is integral to the fuel line on a diesel engine fuel prior to the filter to keep paraffin crystals from stopping fuel flow. The heater warms the fuel by -7°C
In-Line Injection Pump
An Injection pump with a separate cylinder and plunger for each engine cylinder. Each plunger is rotated by a rack to determine metering via ports in the body of the pump and helical cuts on the pump plungers. The plungers are driven off a camshaft, which usually incorporates a centrifugal or electronically controlled timing advance mechanism.
In-line power steering
Power-assisted steering applied within the steering box or rack
In-line pump
A pump whose suction and discharge branches are arranged in line for direct installation into the pipework; special foundations are unnecessary, and the absence of shaft couplings eliminates alignment problems
In-line six
An engine with six cylinders in a row

In-line six-cylinder engine

In-line six-cylinder engineIn-line six-cylinder engine

An engine type that is longer and heavier than four or five cylinder in-line engines, but are generally smoother and more powerful. Before the era of front-wheel drive vehicles, this six-cylinder engine was the common entry level engine. Most were not mounted transversely and thus allowed a lot of working room on either side of the engine. Chrysler Corporation slanted its six-cylinder at a 30° angle which lowered its center of gravity.

Inline three
An engine with 3 cylinder in a row
In molded
A process of manufacturing a helmet in which the outer shell is pressed on to the inner shell so that the helmet is more resistant to wear and tear.
  1. Space occupied in a product container.
  2. A measurement of liquid cargo in a tank. It is the distance from the top of the cargo to the bottom of the tank. It is the opposite of ullage.
Inner attachment face
The part of the brake disc directly fixed to the wheel hub
Inner bottom
On a ship, the watertight plating which is laid over the frames and longitudinals. It forms the inner layer of the double bottom of the hull. Also called tank top.
Inner cap nut
(sleeve nut) A securing device on a dual mounted disc wheel type where it threads directly on the stud and holds the inner wheel in place against the hub.

Inner cone
A small, innermost part of the flame at the tip of a blowtorch, the shape of which indicates the torch adjustment
Inner Construction
All the braces, brackets, panels of the vehicle’s body which give it strength. In contrast with Outer construction
Inner cylinder
The working chamber of a double-tube shock absorber
Inner dead center
Inner Deck Board
Any deck board located between the end deck boards.
Inner fender panels
The vertical panels mounted to the left and right of the engine bay that provide the mounting flanges for the fenders and the top suspension attachment
Inner headlight
The inner one of twin headlights usually for high beam only. The opposite is Outer headlight
Inner liner
The innermost layer of a tubeless tire which provides an airtight barrier
Inner mounting face
Inner Packaging
Also known as Dunnage, includes materials such as foam, paper, or wood used to minimize movement within the container.
Inner race

Bearing RaceBearing Race

The inner track or ring that provides a contact surface for the balls or rollers in a bearing.

Inner Shell
A plated surface or shell inside the outer shell plating, used as additional protection in case of collision or other accidents. The space between the inner and outer shells is often used as a storage space for liquid ballast or cargo.
Inner sill
Inner sill
The hidden part of the sill located behind the outer sill panel, which serves to reinforce the underbody. It is also called longitudinal member or side member
Innerspring seat
A sturdy, sofa-like seat design using spring coils as damping elements; used mainly by Mercedes-Benz.
Inner tube
A doughnut-shaped rubber or latex air chamber which normally is inserted into a non-tubeless tire to hold pressurized air. It contains an air valve to inflate the tube.
A fabric used in clothing to provide comfort in all seasons as well as moisture transfer. Innova’s hydrophobic qualities facilitate movement away from the skin. Innova does not retain odor and resists damage from perspiration. Innova has the lowest thermal conductivity of any fiber and possesses the lowest moisture regain of any fiber for shorter drying time.
  1. Not organic, i.e., composed of matter other than animal or vegetable. In technical terms, any substance that is not a carbon compound (with the possible exception of the oxides and sulfide of carbon)
  2. Pertaining to or composed of chemical compounds which do not contain carbon as the principal element, i.e., matter which does not come from plants or animals. The opposite is Organic
In-place recycling
Input shaft
The shaft delivering power into a mechanism. The shaft from the clutch into the transmission is the transmission input shaft. Also called clutch shaft.

Input Signals
Input variable
The object of measurement and control; e.g., pressure, temperature, etc.
  1. When referring to bearings it indicates a replaceable shell-type bearing made to extremely close tolerances and generally used for Main bearings and Connecting rod bearings.
  2. When referring to valves it indicates replaceable valve seats made of hard, heat-resisting metal that are screwed or shrunk into the cylinder head.
  3. When referring to spark plugs it indicates replaceable threads which are installed into damaged spark plug holes so that spark plugs can be installed. Sometimes known by the trade name Heli-coil®.
  4. Piston liners or cylinder sleeves.
  5. As a verb, it is the technique of permanently joining plastics and other materials, e.g., embedding steel clips in a molded plastic cover. Molded-in inserts are placed into the injection mold cavity so that the melt flows around them during injection; post-molding inserts may be installed by press-fit or ultrasonic methods.
Insert bearing
A removable, precision made bearing which insures specified Clearance between bearing and shaft.

Inserted Packing Red lead
Soaked canvas strips placed between connections that cannot be caulked successfully; stop waters.
Insert socket
A socket for use with a slogging ring wrench which raises the wrench above the surface, thus preventing hammer damage to floor or equipment
Insert tap
inside caliper
Inside caliper
Inside caliper
A machinists’ caliper used to check inside dimensions.

Inside corner weld
Two metals fused together; one metal is held 90 degree to the other. The fusion is performed inside the vertex of the angle.
Inside diameter
(ID) The internal diameter of a cylinder or tube
Inside micrometer
A precision measurement tool used to take accurate measurement of inside surfaces.
Inside pry spoon
A specialized pry bar designed to reach behind brackets and reinforcing bars to pry the metal. The pointed end of the inside pry spoon is placed at the high point of a dent, which is then forced out
Inside spring caliper
An inside caliper with spring for accurate setting
Exposure to the rays of the sun
A type of examination which serves to evaluate the operating condition of a component or system; the inspection may identify the need for servicing or repair.

Inspection and Maintenance Programs
(IM) In-use emission testing programs, primarily for passenger cars, used by some U.S. states to identify vehicles that cause excessive emissions which contribute to air pollution.
Inspection lamp
A British term for a Trouble-shooting light.
Inspection lot
Certain quantity of a particular item chosen at random for quality testing
Inspection mirror
A tool used to inspect hidden areas on automotive parts. It consists of a long rod (sometimes telescoping) with a small mirror at one end.
Inspection pit
A pit in the floor of a garage providing working space underneath a vehicle
The representative of the engineer who is authorized to inspect and report on contract performance.
To put something in position ready for use
Putting something in position ready for use. The opposite is removal

Installed height
  1. The height at which something is placed in position.
  2. The spring’s measured length or height, as installed on the cylinder head. Installed height is measured from the spring seat to the underside of the spring retainer
Installed market
Installed nameplate capacity
  1. An automotive mechanic whose sole responsibility is to install accessory equipment into a vehicle (e.g., radio, antenna, CD player, GPS)
  2. A tool used to install a component in place
Instant spare
An emergency inflator
Institute For Highway Safety
Institute of the Motor Industry
(IMI) British organization for managers in the motor industry
Used broadly to denote a device that has measuring, recording, indicating, and/or controlling abilities.

Instrument cluster
  1. An array of separate gauges in one housing; a major component of the instrument panel including analog or digital instruments and indicators, but no controls except for the trip mileage reset button on some cars.
  2. Several gauges integrated into one instrument, making one unit combining several functions, e.g., engine temperature, oil pressure and fuel gauge; if one gauge fails, the entire instrument cluster must be replaced
Instrument light
A light within a gauge or instrument panel that is illuminated to provide visiblity.
Instrument panel
(ip) The panel below the windshield and/or the cowl top panel and attached to the dash panel or fire wall, and which accommodates the instruments and controls. Also called dash, dashboard, or fascia
Instruments and controls
A general term covering all gauges, indicators, switches, regulators, and buttons
To cover with non-conducting material, so as to prevent the transmission of heat, electricity, or sound
Insulated trailer
A trailer designed for transporting commodities at controlled temperatures, usually provided with refrigerating and/or heating equipment.
Insulating cap
The insulated top of the coil tower
Insulating tape
PVC tape (usually black) for wrapping around electrical connections
  1. Any material which does not conduct electricity. It is used to prevent the flow or leakage of an electrical conductor.
  2. Any material which does not readily conduct heat. Used to keep heat or cold out of something.
  3. The process of insulating.
  4. (INSUL) In an electric motor, usually classified by maximum allowable operating temperature
    • class A 105°C
    • class B 130°C
    • class C 155°C
    • class H 180°C
Insulation, electric
Substance which has almost no free electrons.
Insulation, thermal
Material which is a poor conductor of heat; used to retard or slow down flow of heat through wall or partition.
  1. A unit made of a material that will not conduct electricity. The electricity in a copper wire covered with a plastic sleeve (insulator) cannot penetrate the sleeve.
  2. A material that prevents or slows the transfer of heat from one area to another
  3. A material which tends to resist the flow of electric current
Insulator block
A fiber or rubber block that insulates the carburetor from engine heat, used with flange mounted carburetors.
Insulator nose
The tip of a spark plug

Insulator tip
The tip of a spark plug
Insurance Institute for Highway Safety
(IIHS) A US body for determining the crashworthiness of vehicles in order to determine insurance costs.
Insurance premium
A regular payment for an insurance policy
Abbreviation for interior.
  1. Abbreviation for Integrator (replaced by ST FUEL TRIM)
  2. Abbreviation for Intermittent duty cycle
Intake air temperature sensor
A sensor located in the induction system that provides an electrical output proportional to the temperature of the air or air/fuel mixture
Intake cam
The cam responsible for the actuation of the inlet valve in DOHC engines
Intake camshaft
The cam responsible for the actuation of the inlet valve in DOHC engines
Intake charge
The mixture of fuel and air that flows into the engine.
Intake configuration
Intake manifold
Intake manifold
Intake manifold
  1. A sleeve or flange made of rubber or metal to attach to the intake port.
  2. The connecting tubes between the base of the carburetor and the port openings to the intake valve or intake ports. The air-fuel mixture travels from the throttle body into a chamber called the plenum which feeds individual tubes (called runners) which lead to the individual intake port. Its purpose is to transfer the air-fuel mixture to each cylinder. It is usually an aluminum casting or a GRP molding, with one intake opening and as many outlets as there are cylinders in the engine. Also called inlet pipe.
  3. The British term is inlet manifold
Intake manifold heater
Intake over exhaust engine
(IOE engine) An engine design used on early cars. Also called F-head engine. The intake and exhaust valves are arranged vertically in a lateral chamber of the combustion chamber and face one another; the side valve (usually the exhaust) is actuated directly by the camshaft, which usually rotates in the cylinder block; the overhead valve (usually the intake) is located in the cylinder head and actuated via a pushrod and rocker arm
Intake pipe
The duct, typically an alloy manifold, between the throttle and cylinder head; the absolute pressure in the induction pipe, the so-called intake vacuum, is indicative of engine load and is used to control many engine-related functions. The British term is induction pipe
Intake plenum
Intake port

Intake portIntake port

  1. The passage in the cylinder head which connects the intake manifold to the intake valve through which the fuel-air mixture proceeds on its way to the cylinders. The British term is inlet port.
  2. An opening or passage which directs the flow of air and fuel into the engine. In a four-stroke engine, the intake port is located in the cylinder head. In a two-stroke engine, the intake port is located in the cylinder or crankcase.
  3. The passage through which brake fluid flows in the master cylinder from the reservoir to refill the low-pressure area ahead of the cup on the return stroke
Intake stroke

Intake strokeClick image to supersize

In a Four-stroke cycle engine, it is the piston’s first stroke down in pulling fuel and air into the combustion chamber as it causes a partial vacuum. The phase of the 4-stroke cycle during which the intake valve is open and the piston descends from TDC to BDC, drawing air (in a diesel engine) or an air/fuel mixture (in a spark ignition engine) into the cylinder. The British term is induction stroke

Intake temperature sensor
Thermistor used by the computer to monitor the temperature of the air entering the engine.
Intake timing
Amount of time a two-stroke engine intake port is open, expressed in crankshaft degrees or piston position.
Intake tract
A branch of the intake manifold leading to an Intake port.
Intake valve

Intake valveIntake valve

The Poppet valve that opens to permit the fuel mixture into the cylinder. It closes during the compression and combustion strokes. Some engines have more than one intake valve to each cylinder. The British term is inlet valve.

Intake valve closes
(IVC) A mark on a valve-timing diagram.


Intake valve opens
(IVO) A mark on a valve-timing diagram.


In-tank fuel pump
An electric fuel pump that keeps pressure in the fuel line prior to the main fuel pump to prevent vapor lock.
IntegraClick logo for books on

A model of automobile from Acura

An essential component of something.

Integral ABS
An ABS in which the power booster and components of the standard and ABS brake systems form a single hydraulic unit.
Integral alternator/regulator
(IAR) a type of regulator mounted at the rear of the alternator
Integral backpressure transducer EGR valve
Combines inputs of exhaust backpressure and EGR ported vacuum into one unit. Requires both inputs to operate on vacuum alone there are two common designs Poppet and tapered pintle
Integral body and frame construction
Integral collector storage
(ICS) A solar thermal collector in which incident solar radiation is absorbed directly by the storage medium.
Integral color anodizing
An anodizing process in which the color is produced by using special electrolytes
Integral equipment
Any device or system that is designed for a vehicle and installed in it by the manufacturer, rather than being added on to a finished vehicle at a later date.
Integral frame
Integral fuel filter
A fuel filter which is part of the fuel pump or part of the Carburetor rather than one that is attached to a fuel line (in-line fuel filter).
Integral horsepower motor
In terms of horsepower, an Open enclosure electric motor built in a frame having continuous rating of 1 hp or more at 1700-1800 rpm. In terms of size, an integral hp electric motor is usually greater than 9 inches in diameter, although it can be as small as 6 inches
Integrally molded linings
disc brake pad sets that have the linings cured integrally with the pad plates.
Integral molded seat
A seat with integrated 3-point seat belt
Integral part of
A necessary part of something, e.g., the Cam lobe is an integral part of the camshaft.
Integral-type power assisted steering
Integral-type power steering
Integral vacuum booster
A vacuum booster that installs between the brake pedal and the master cylinder. Integral boosters are actuated by brake pedal movement.
Integrated child safety seat
A fold-down child safety seat located in the center of the rear seats that is part of the original car. This seat includes seat belts, and are generally not as good as aftermarket safety seats. They are not as adjustable or comfortable. There is generally little or no side protection and the child normally must sit with his legs sticking straight out. When not in use, the seat can be folded away, much like an armrest.
Integrated child seat
A rear seat that can be converted into a child seat.

Integrated circuit

  1. A circuit that incorporates multiple transistors and other semiconductors to a single circuit, sometimes called a chip.
  2. A complete electronic circuit consisting of numerous transistors and other solid state devices, and formed on a single silicon semiconductor chip.
Integrated circuit board
Electronic circuit made from transistors, resistors, etc., all placed into a package referred to as a chip, since all circuits are on one base of semiconductor material.
Integrated Direct Ignition System
(IDI) A distributorless ignition system consisting of two separate ignition coils, an ignition module, a secondary conductor housing mounted to an aluminum cover plate, a crankshaft sensor, and electronic spark timing
Integrated roll cage
The cage or framing of the car serves the dual purpose of protecting the passenger while also creating a place to hang all the car’s components — engine, steering, sheet metal, etc. An integrated roll cage is one that is claimed to be especially safe and designed to protect the passenger in the case that the car rolls. It is called integrated because it is part and parcel of the overall framing for the car’s components and thus sturdier.
Integrated safety belts
Consist of a shoulder belt and a lap belt. Whereas the cars of the 60s had the option of being ordered without seat belts, today’s cars have an integrated safety belt as standard equipment.
Integrated system
An anti-lock brake system with the brake booster and hydraulic modulator integrated into a unit with the master cylinder
Intellectual property rights
(IPR) The right to possess or control the use of intellectual property, such as trademarks, copyrights, patents and trade secrets.
Intelligent Transportation Systems
(ITS) A traffic monitoring system that uses electronics to communicate with motorists. Examples include variable message signs and video traffic cameras.

Intelligent Vehicle Highway Systems
(IVHS) Blanket term for a wide array of technologies, including electronic sensors, computer hardware and software and radio communications. The purpose of IVHS is to increase efficiency of use of existing highways, reducing travel time, fuel consumption, air pollution and accidents. There are five functional areas:

  • Advanced Public Transportation Systems (APTS)
  • Advance Traffic Management Systems (ATMS)
  • Advance Traveler Information Systems (ATIS)
  • Advanced Vehicle Control Systems (AVCS)
  • Commercial Vehicle Operations (CVO)

A more recently coined term, Intelligent Transportation Systems, encompasses both IVHS and modes of transportation other than highway, such as rail.

The disc between the driven plates in a twin plate clutch
To increase or concentrate, such as to increase the voltage of an electrical current.
Interactive wishbone
The patented suspension system used on the front of the new Lotus Elan which maintains precise suspension geometry without transmitting undue road harness to the passengers. The result is the elimination of torque steer and bump steer, and a very comfortable ride.
Inter-axle differential
Gear device equally dividing power between the axles and compensating for unequal tire diameters. Also called Center differential
Inter-cable adjuster
An adjuster built into some parking cables that allows the outer housing to be made longer or shorter to adjust the parking brake.
Intercell connector
A lead strap or connector that connects the cells in a battery
Inter-cell link
An electric conductor that carries electric current between the adjacent cells of a battery
Passing freight from one carrier to another between lines.
Interchangeable head torque wrench
A wrench that does not have the usual square drive for use with sockets, but is designed to accept special interchangeable heads
Interchannel competition
The rivalry between different channels of the distribution system. For example, independent retailers competing with manufacturers’ outlets.
Intercity bus
A transportation vehicle designed for high speed, long distance travel; equipped with front doors only, high backed seats, and usually restroom facilities.
  1. Domestic shipping routes serving more than one coast.
  2. Made in separate parts; between frames, beams, etc.,the opposite of continuous. (Floors are continuous; longitudinal girders are intercostal in most cargo vessels.).
Intercoat adhesion failure
A situation in which one coat of finish peels off or can easily be stripped off with masking tape from another layer underneath. This may be caused by excessive bake time of coatings, resulting in too hard a finish, poor flatting of coats, providing poor keying of coats, or very low film thickness
  1. A device which cools the air entering the carburetor or fuel injection system. Colder air has more oxygen molecules than warm air. Thus cooler air gives more power and better fuel economy. An intercooler looks like a radiator. It contains large passages for the intake flow, and uses either outside air or water directed over it to lower the temperature of the intake flow inside. Also called a charge-air cooler or charge cooler. Compare aftercooler.
  2. A heat exchanger for cooling gas between stages of a multistage compressor with a consequent savings in power.
  3. Intake manifold cooled by circulated water.
  1. The temperature reduction of the charge air between compressor and engine
  2. Cooling the engine intake air after the turbocharger and prior to introduction into the cylinder.
A structure made in separate parts; between each floor, frame or beam, etc instead of made in one continuous length spanning all the floors, frames, or beams
Intercrystalline corrosion
A small outbreak of rust occurring along crystal boundaries of metals or alloys
Interest rate
  1. Difference in angle between mating surfaces of a valve and a valve seat.
  2. The noise from the ignition system that affects radio and TV reception. Suppressors are used to minimize interference and on modern vehicles the main suppressors are the spark plug leads.
Interference angle
Valve seat angle cut slightly less than the valve face angle. The valve face seats a few seconds after initial engine start-up.
Interference fit
A condition of fit (contact) between two parts that requires pressure to force the parts together. Usually the shaft is slightly larger than the hole so that they must be pounded or forced or driven together. Also called Force fit, Press fit, or Drive fit.
Intergovernmental Panel on Climate Change
(IPCC) A panel established jointly in 1988 by the World Meteorological Organization and the United Nations Environment Program to assess the scientific information relating to climate change and to formulate realistic response strategies.
Intergranular corrosion
A small outbreak of rust occurring along crystal boundaries of metals or alloys
The inside of a vehicle
Interior light
The Courtesy light which illuminates when the doors are opened or when an interior switch is activated.
Interior light switch
There are two types of switches which turn on the interior lights One is located on the door posts and is activated when the door is opened or closed. The other is found on the instrument panel and may be incorporated into the headlight switch.
Interior mirror
The rear-view mirror located centrally near the top of the windshield.

Interior noise level
The level of noise inside the vehicle, typically in the range from 45-90 dBA from idle to full throttle; at 70 mph between 66-87 dBA
Interior payload
The amount of weight that a vehicle can carry. The capacity of the usable area in the vehicle’s interior. It is defined by cubic feet. This includes the seating area for passengers as well as the cargo space
Interior trim
The panels, linings, decorative facings, upholstery, and covers inside a vehicle
Interleaf friction
The friction between individual leaves of a leaf spring
Interline Freight
Freight moving from origin to destination over two or more transportation lines.
  1. To fit gear train members together.
  2. A device in a change-speed gearbox which prevents two gears from being engaged at the same time.
  3. A control to prove the physical state of a required condition and to furnish that proof to the safety shutoff device circuit.
Interlock Switch
Firm or organization that operates between the producer of the goods and the end purchaser. Thus, the members of the distribution channel noted above are intermediaries or ‘middlemen’.
Between two things or two extremes
Intermediate car
A designation no longer used because even full-size cars are now about the size of what was the compact car. In 1970, for instance, a Chevrolet Impala was a full-size car, a Chevelle was an intermediate, a Nova was a compact. When cars smaller than the Nova came out (i.e., Chevette), they were called sub-compacts.
Intermediate coat
Any coat of paint between the first coat (primer) and last coat (finish)
Intermediate drive plate
A disc between the driven plates in a twin plate clutch
Intermediate gear
Any gear in the auto transmission between first and high. Usually refers to second or third gears
Intermediate grade gasoline
A grade of unleaded gasoline with an octane rating intermediate between Regular and Premium. Octane boosters are added to gasoline to control engine pre-ignition or knocking by slowing combustion rates.
Intermediate hold
A term dating from the early days of three-speed automatic transmissions; today represented by the position 2 on the selector quadrant
Intermediate lever
A parking brake linkage lever (other than the parking brake pedal, lever, or handle) used to increase parking brake application force.
Intermediate plate
A disc between the driven plates in a twin plate clutch
Intermediate rim taper
A rim with one tapered bead seat of 5° at the fixed flange.
Intermediate rod


Intermediate shaft
A rotating shaft joining two other shafts
Intermetallic compound
An alloy of two metals in which a progressive change in composition is accompanied by a progression of phases with varying crystalline structures
Not constant but occurring at intervals.
Intermittent duty cycle
(INT) An electrical motor which never reaches normal operating (equilibrium) temperature but is permitted to cool down between operations is operating under intermittent duty conditions. Compare Continuous Duty Cycle
Intermittent cycle
Cycle which repeats itself at varying time intervals.
Intermittent failures
A defect that appears for only a short time with no definitive pattern. Usually occurs as a result of wear and is often a precursor to a permanent failure.
Intermittent fault
A problem which comes and goes (and annoyingly never occurs when the car is taken in to the garage for repair!)
Intermittent weld
Joining two pieces and leaving unwelded sections in the joint.
Intermittent wiper control
A device which operates the wipers at preset intervals; typically adjustable from 2 to 40 seconds. It usually includes a mist action which makes only one swipe and then stops. Most often used in conditions of light drizzle or snow, mist, and spray from other vehicles
Intermittent operation
A system which is not activated in a regular pattern, but with specified delays.
Using two or more modes of transportation: rail, truck or ship. The stock can move over sea by ship, over land by rail and then, at the main rail switch, the container is removed and put on truck chassis. The stock is then carried by truck to the Distribution Centers.
Intermodal Container
A cargo container designed for high-speed transfer of cargos between different transportation modes. Typically seen around harbor ports, railway yards, and cargo storage facilities.
Intermodal Surface Transportation Efficiency Act of 1991
(ISTEA) An omnibus act that further integrates the national intermodal surface transportation system and authorizes funds for highway construction, highway safety programs, and mass transit programs. ISTEA seeks a national intermodal surface transportation system that is economical, energy efficient, and environmentally sound. Section 1008 of the ISTEA establishes the Congestion Mitigation and Air Quality Improvement Program which can provide funds to support alternative-fuel and alternative-fuel vehicle programs.
Intermodal transportation
Transportation that involves the interchange between transportation modes, such as automobiles, mass transit such as buses and railway. Intermodal transportation enables people and goods to be consolidated into larger groups that can be transported at lower costs. In addition to reducing costs, it enables greater logistic flexibility than can also reduce congestion and travel time.
Internal bowl vent
A tube designed to vent excess fuel vapors from the fuel bowl back into the carburetor during acceleration and cruising conditions
Internal chain drive
Transmission that uses an internally housed chain to drive one or more shafts.
Internal circlip pliers
A special pliers with pointed jaw tips for the installation and removal of internal circlips
Internal Collector Storage
(ICS) A solar thermal collector in which incident solar radiation is absorbed by the storage medium.
Internal combustion engine
(ICE or IC) An engine that burns fuel within itself as a means of developing power (unlike an External combustion engine such as a steam engine). Although the term internal combustion engine covers all types of reciprocating and rotary engines, it is typically used with reference to four-stroke gasoline and diesel engines
Internal cooling
Engine cooling provided by oil, fuel mixtures, and valve overlap.
Internal damage
Injury to the body shell that is not usually visible from the outside. Such damage is often caused by rust from the inside of panels and fenders, so the damage becomes visible only in an advanced state of decay
Internal diameter
Internal gear
An internally toothed Annular gear
Internal gear pump
A gear pump which has one rotor with internally cut teeth meshing with an externally cut gear idler; a crescent-shaped partition is used to prevent liquid from passing back to the suction side of the pump; a typical oil pump, characterized by quiet operation and high capacity
Internal manifolding
A system with a self-contained reactant delivery system similar to a boxed fuel cell system that would only require connections to the reactant tanks to become operational.
Internal micrometer
A Micrometer for inside measurements such as distances between two parallel surfaces or inside diameters of cylinder and main bearing bores
Internal mix air cap
A special type of air cap for spray guns. Air and material are mixed inside the gun and are ejected through a single orifice. This design is used only for pressure-feed guns, primarily for spraying heavy viscous materials. Compare External mix air cap
Internal reforming
Internal resistance
The resistance inherent in a voltage source, such as a battery. The internal resistance of a battery is made up of several individual resistances, e.g., between the plates and the electrolyte, the plate resistances, the resistance of the electrolyte to ion flow, and internal connectors
Internal Resistance Loss
Internal snap ring
A split ring held in place by its own tension within a groove cut around the bore of a hole. Compare External snap ring.
Internal thread
The thread on the inside of a nut or similar into which the external thread of a bolt or screw fits. Also called female thread
Internal tooth lock washer

Internal tooth lock washerInternal tooth lock washer

A lock washer with serrations on the inside hole. In application, these serrations or teeth bite into the nut, bolt, or material to prevent the nut from easily backing out. Compare external tooth lock washer

Internal vane pump
internationalClick image for books on

An automobile manufacturer. Also called International Harvester

International bunker fuels
Internationale de l’Automobile
Internationale du Sport Automobile
International load line certificate
A certificate issued after the vessel has been surveyed and load lines marked on her sides.
International Metric Thread System
A thread form similar to the American standard, excepting the depth which is greater. There is a clearance between the root and mating crest fixed at a maximum of 1/16 the height of the fundamental triangle or 0.054 x pitch. A rounder root profile is recommended. The angle in the plane of the axis is 60 degrees and the crest has a flat like the American standard equal to 0.125 pitch.
International Motorsports Association
(IMSA) The sanctioning body of sports car prototype racing in the United States. Current categories include World Sports Cars (WSC) a series for purpose-built race cars, GTS-1 for vehicles resembling street cars but which have custom-made chassis and highly modified engines and GTS-2 which are race cars made from street cars but with modified engines, transmissions and suspensions. Major events sanctioned by IMSA include the Rolex 24 Hours of Daytona and 12 Hours of Sebring, the longest running sports car race in the United States.
International Standards Organization
(ISO) A Geneva-based organization established (in its present form) in 1947 to standardize units of measurement and technical design
International tonnage certificate
A certificate issued by a government department in accordance with the International Convention of Tonnage Measurement of Ships stating the gross and net tonnages
International waterways
International straits, inland and interocean canals and rivers separating the territories of two or more nations which are can be navigated by both merchant ships and warships with no restrictions
Interprovincial highway
A broad road (usually multi-laned) that crosses two or more provinces of Canada but is not designated with the same number in each province. See Trans-Canada Highway
Interrupted ignition source
An ignition source which is automatically ignited or energized when the equipment is called on to operate and which remains ignited or energized during the main burner Flame-Establishing Period. The ignition source is automatically extinguished or de-energized when each main burner Flame-Establishing Period is completed.
Interrupted pilot
A pilot that is automatically lighted each time there is a signal for initialization. The pilot fuel is cut off automatically at the end of the main burner flame-establishing period.
A road junction.

Interstate Commerce
Exchanging goods between buyers and sellers in two or more states.
Interstate commerce commission
(ICC) US Government body which controls the design and construction of pressure containers. The U.S. federal body formerly charged with enforcing Acts of Congress affecting interstate commerce. The ICC was decommissioned in 1993.
Interstate companies
Natural gas pipeline companies subject to Federal Energy Regulatory Commission (FERC) jurisdiction.
Interstate highway

Interstate shieldInterstate shield

A broad road (usually multi-laned) that crosses two or more states of the U.S. and is designated with a low number and maintains that same number in each state.

Interstate Trucking
Trucking commerce crossing state lines.
Interval operation
Interstate pipeline
Any person engaged in natural gas transportation subject to the jurisdiction of Federal Energy Regulatory Commission: (FERC) under the Natural Gas Act.
In the grass
Trucker slang for the median strip as in ‘We got a smokey in the grass.’
Something that can affect a person’s behavior, perception, mood or alertness
Intrachannel competition
Rivalry between channel participants at the same level in the distribution channel. For example, department stores competing with one another.
Domestic shipping routes along a single coast.
Intracorporate Hauling
Trucking and delivery between two points within one state.
Intrastate Commerce
When all business between buyers/sellers is carried on within state.
Intrastate companies
Companies not subject to Federal Energy Regulatory Commission (FERC) jurisdiction.
Intrastate pipeline
Any person engaged in natural gas transportation (not including gathering) that is not subject to the jurisdiction of the Commission under the Natural Gas Act (other than any such pipeline that is not subject to the jurisdiction of the Commission solely by reason of Section 1(c) of the Natural Gas Act).
Intrastate Trucking
Trucking commerce within the same state.
Intrusion beam
Intuitive control
A switch or device which the manufacturer believes is self-explanatory to operate. However, the user may not understand its operation.
Intumescent Mat
Ceramic fiber mat which irreversibly expands after exposed to high temperature. Usually contains vermiculite. Intumescent mats are used in the canning of catalytic converters and diesel filters to hold the ceramic substrate inside the steel canister.
In-Use Deterioration
(IUD) The effect of time and use on vehicle performance and emissions.
In-use vehicle
A vehicle that is:

  • Registered with the Government of one or more States, the District of Columbia, the Commonwealth of Puerto Rico, or the Virgin Islands; or
  • The vehicle is owned or operated by a Government or military organization within the United States that is not required to register vehicles with the Government agencies listed under #1 above. For example, civilian Federal vehicles are generally not required to register with the State Government in which they are assigned.
Vehicles specially designed or constructed for people with disabilities. This does not apply to conventional motor vehicles which have been modified for disabled persons and which are permitted to be on the road.
The book value of inventory owned and held in a particular country.
The amount of goods on hand or reported to be on hand.

Inventory System
Perpetual Inventory System.
Inventory Turns
The number of times inventory turns is calculated using the following method: a) Sum the Inventory In and the Inventory Out, and then divide by 2 to arrive at the Throughput. b) The number of Inventory Turns is equal to the Throughput divided by the Average Inventory.
Inverse Voltage
Inverted telescopic forks
An older name for Upside-down forks
Inverted-tooth chain
A type of chain with teeth formed on its links to engage with the teeth in the sprockets. Silent chains drives are not truly silent. The links in a silent chain drive, however, engage with the sprocket teeth with little impact or sliding, and as a result a silent chain produces less vibrations and noise than other chains. The amount of noise generated by a silent chain drive depends of many factors including sprocket size, speed, lubrication, load, and drive support. A link belt silent chain includes removable links joined by rivets or interlocking tabs. These chains offer the advantage of installation without dismantling drive components, reducing inventory, and increasing temperature ranges. Also called Silent chain
  1. A vehicle brand of which the 1925-1938 models are classic cars.
  2. A model of automobile manufactured by Buick Division of General Motors from 1959-63
Invisible glove
Trucker slang for traffic tickets as in ‘You got a smokey at the 57 yardstick giving out invitations.’
Abbreviation for input/output, for computer data transmission
Abbreviation for Inlet over exhaust
IOE engine
  1. An electrically charged particle formed by losing or gaining electrons; particles of this type make a solution of certain chemicals a conductor of electricity
  2. Group of atoms or an atom electrically charged.
Ion exchange
Reversible exchange of ions adsorbed on a mineral or synthetic polymer surface with ions in solution in contact with the surface. A chemical process used for recovery of uranium from solution by the interchange of ions between a solution and a solid, commonly a resin.
Ionic-current measuring method
A measure of the conductivity in the spark gap in order to select a spark plug of the correct heat range
Ionic-current measuring technique
A measure of the conductivity in the spark gap in order to select a spark plug of the correct heat range
The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, and nuclear radiation can cause ionization.
  1. Abbreviation for Instrument Panel
  2. Abbreviation for British Institute of Petroleum
Abbreviation for Instrument Panel Cluster
Abbreviation for Intergovernmental Panel on Climate Change
  1. Abbreviation for Injector Pressure Regulator
  2. Abbreviation for Intellectual Property Rights.
Abbreviation for Integrated Relay Control Module
IR drop
Electrical term indicating the loss in a circuit expressed in amperes times resistance (I x R) or voltage drop.
A display of the spectrum of glittering, shimmering colors; often changing as the position or angle from which they are observed, changes
Abbreviation for Integrated Road Information System
Ir loss
Losses created by the resistance to the flow of ions in the electrolyte and resistance to flow of electrons through the electrode and bipolar plate materials. Because both the electrolyte and fuel cell electrodes obey Ohm’s law, the ohmic losses can be expressed by the equation Ohm = iR. Also called ohmic polarization
  1. (Fe) A metal used for making steel. In the steel industry, iron is the name of the product of a blast furnace containing 92 to 94 percent iron. Other names for blast furnace are pig iron and hot metal.
  2. A colloquial term for any automobile.
  3. A tire lever or tire iron.
  4. A soldering iron.
  5. An old used car valued at nothing more than the price of iron.
Iron Butt Rally
The most grueling long-distance motorcycle rally in the world. To finish the rally requires that you ride at least 10,000 miles in 11 days
Iron core
IR remote control
Abbreviation for Institute of Road Transport Engineers A British organization set up to increase the competence and professionalism of vehicle drivers and owners
Abbreviation for Independent rear suspension.
Abbreviation for Idle speed control
ISC motor
Abbreviation for Idle speed control motor
Abbreviation for International Six Day Trial (a motorcycle race)
Isherwood System
A system of building ships in which the main framing is longitudinal or fore and aft, instead of transverse as in ordinary ships.
Abbreviation for International Standards Organization
(C4H10) A normally gaseous branch-chain hydrocarbon. It is a colorless paraffinic gas that boils at a temperature of -17.8°C. It is extracted from natural gas or refinery gas streams.
(C4H8) An Olefinic hydrocarbon recovered from refinery processes or petrochemical processes.
Isochronous governor
A device which maintains constant engine speed regardless of changes in the load being carried.
ISO flare
The type of brake line flare made popular by the International Standards Organization
(C6H14) A saturated branch-chain hydrocarbon. It is a colorless liquid that boils at a temperature of 69°C.
Name for an engine/swingarm rubber mounting system used by Norton on its early Commando motorcycles
Isolated operation
A mode of operation in which the fuel cell power plant is separated, electrically and mechanically, from all other sources of electrical energy.: (Sell also GRID ISOLATED).
Isolate the battery
  1. The action that occurs when the anti-lock brake system isolates one or more wheel brakes from hydraulic pressure produced by the master cylinder, allowing the ABS to take over control of braking pressure from the driver
  2. The amount of sunlight reaching an area. Usually expressed in milliwatts per square centimetre.
An item that prevents interaction between two components
A refining process that alters the fundamental arrangement of atoms in the molecule without adding or removing anything from the original material. Used to convert normal butane into Isobutane: (C4), an alkylation process feedstock, and normal pentane and hexane into isopentane: (C5) and isohexane: (C6), high-octane gasoline components.
Liquid hydrocarbon used to determine the octane rating of fuels; (see also octane number)
A saturated branched-chain hydrocarbon: (C5H12) obtained by fractionation of natural gasoline or isomerization of normal pentane.

Changes of volume or pressure under conditions of constant temperature.
Isothermal expansion and contraction
Action which takes place without a temperature change.
Forms of the same chemical element that differ only by the number of neutrons in their nucleus. Most elements have more than one naturally occurring isotope. Many isotopes have been produced in reactors and scientific laboratories.
A vehicle brand of which all models from 1919 except Tipo 8C Monterosa are classic cars.
Abbreviation for Input Shaft Speed
Abbreviation for Intermodal Surface Transportation Efficiency Act of 1991
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Abbreviation for Ignition Timing Adjustment
A vehicle brand of which models build during 1925-1948 are classic cars.
Abbreviation for Ignition Timing Control System (Honda)
Abbreviation for Institute of Transportation Engineers
  1. Abbreviation for Idle tracking switch. An input device that sends a signal to the control module to indicate throttle position
  2. Abbreviation for Intelligent Transportation Systems. Uses electronics to monitor traffic and communicate with motorists. Examples include variable message signs and video traffic cameras. See IVHS


Abbreviation for In-Use Deterioration

  1. Abbreviation for Inlet valve closes
  2. Abbreviation for ‘Individually Controlled Ventilation’ as introduced on 1933 Fisher body LaSalles
Abbreviation for Intelligent Vehicle Highway Systems — A general term for a wide variety of technologies, including electronic sensors, computer hardware and software, and radio communications. The purpose of IVHS is to increase efficiency of use of existing highways, reducing travel time, fuel consumption, air pollution, and accidents. A more recently coined term, Intelligent Transportation Systems (ITS), encompasses both IVHS and modes of transportation other than highway, such as rail. (see AVI, AVL, WIM) There are five functional areas

  1. Advanced Public Transportation Systems (APTS)
  2. Advance Traffic Management Systems (ATMS)
  3. Advance Traveler Information Systems (ATIS)
  4. Advanced Vehicle Control Systems (AVCS)
  5. Commercial Vehicle Operations (CVO)


Abbreviation for Inlet valve opens
Abbreviation for Idle Validation Switch
Abbreviation for Integrated Vehicle Speed Control
Abbreviation for Infinitely Variable Transmission.
Abbreviation for Idle vacuum valve
Izod method
An impact resistance test in which the specimen is held as a vertical cantilever beam and is broken by a single swing of a pendulum, with the line of initial contact at a fixed distance from the specimen clamp and from the centerline of the notch and on the same face as the notch
Izod test
An impact resistance test in which the specimen is held as a vertical cantilever beam and is broken by a single swing of a pendulum, with the line of initial contact at a fixed distance from the specimen clamp and from the centerline of the notch and on the same face as the notch