A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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I.F.S.: Independent Front Suspension. Also inertia fuel shut off switch used to switch off an electrical fuel pump or diesel fuel pump solenoid when the vehicle is involved in an accident.
I.R.S.: Independent Rear Suspension.
IA ISA: Idle adjust. Idle speed adjust.
IAT: Intake air temperature sensor used in electronic fuel injection as a correction factor for the quantity of fuel to be delivered.
ICE: In Car Entertainment system.
ICM: Ignition Control Module.
IDI: Indirect injection of diesel fuel into a pre-combustion or swirl chamber in the cylinder head.
Idle: Term used to describe an engine running at a speed when the throttle has not been depressed. Also used to describe a lazy technician...
Idle Air Control (IAC): Idle air control. An air valve on fuel injection systems to increase the air flow and idle speed of a cold engine and during warm up.
Idle Control Components: Parts that are designed to keep the engine idle speed at a set level.
Idle Mixture: The fuel strength or air/fuel ratio.
Idle Speed: Rotational speed of an engine on no-load and minimum throttle setting. Also tick over and curb idle.
Idler Arm: A steering arm parallel to the Pitman arm (drop arm) and connected to it by a centre track rod.
Idler Gear: (1) A gear between two others that does not affect the gear ratio. Any gearwheel between the driving and driven gears in a gear train, the shaft of which serves only to bear and locate the gear, and is therefore 'idle'. The idler gear may serve to reverse the rotation of the driven wheel, so that it rotates in the same direction as the driving wheel. (2) An intermediate or tensioning pulley for a belt drive.
Idling: Describes an engine running at idle speed (usually 700 to 800 rev/min).
Igniter: The part of an air bag unit that sets the inflation process in to action.
Ignition - IGN: Starting of combustion. Setting fire to a flammable substance. In a petrol engine the spark jumping the spark plug electrodes that starts the combustion process.
Ignition Advance: The automatic bringing forward of the ignition spark in relation to the engine speed.
Ignition circuit: The system used to connect components involved in producing a high voltage at the spark plugs.
Ignition Coil: An electrical transformer that increases the battery voltage to a high tension capable of arcing across the gap of spark plug electrodes.
Ignition Coil - IGC: An electrical transformer that increases the battery voltage to a high tension capable of arcing across the gap of spark plug electrodes.
Ignition Distributor: A component in the ignition system that houses the primary circuit switching device and the secondary circuit distribution components.
Ignition Lag: A short delay after injection before the fuel ignites.
Ignition Module: The electronic unit that switches the ignition coil on and off in response to a signal from a pulse generator.
Ignition Switch: The engine ignition and vehicle electrical circuits control switch used by the driver to start and stop the engine.
Ignition Timing: The static and dynamic settings of the ignition distributor or in the engine control module (ECM) that control the ignition coil secondary circuit output and spark for starting the combustion process in the engine.
Illumination: Lighting up, making bright.
Immobiliser: Usually part of an alarm system. It cuts off the ignition or fuel to prevent a vehicle from being started and stolen.
Impact Switch: A switch that operates when the car impacts something. Used as a safety device to cut off a fuel pump.
Impact Tools: Power tools that use a high frequency hammering action for the removal and installation of nuts and bolts, for drilling and chiseling. Impact tools should only be used with sockets, drills and chisels made for that purpose. The use of normal hand tools form impact is hazardous as these may shatter in use.
Impeller: Vaned disc that creates flow by centrifugal force (water pump). In a torque converter it is driven from the engine to force liquid onto the turbine.
Imperial: Old British standard of measurement using yards, feet and inches.
In-line Engine: A engine fitted along the axis of a motor vehicle.
Inboard Brakes: Brake units fitted on the final drive casing and output shafts rather than on the wheel hub and carrier.
Incandescence: Light given off by a high temperature object. Usually describes a bulb filament.
Included Angle: Camber and steering swivel (king pin) inclinations (angles) added together.
Independent Suspension.: Suspension fitted to each wheel.
Indirect Injection: Diesel engine design where fuel is injected into a pre-combustion chamber fitted inside the cylinder head.
Induced Voltage: Naturally occurring voltage in a conductor when subjected a magnetic flux.
Inductance: Property of a coil such that an increase in current causes an increase in magnetism, which in turn tends to prevent the original increase in current. See also Lens's law.
Induction: 1. The drawing in of a gas or fluid.2. Process of causing an electrical potential in a conductor due to relative movement of a magnetic field.
Induction Stroke: First stroke of four stroke cycle when air and fuel enter the engine as the piston moves down the cylinder. Also known as the intake stroke.
Inductive Coil: All coils possess inductance. This is the property that resists changes in current flow.
Inductive Generator: A magnetic/electrical pulse generator used as a sensor in electronic control systems. It uses an iron core and electrical winding to induce an electrical current when passed by a toothed wheel or rotor. Also known as a magnetic pulse generator.
Inductive Sensor: A coil and magnet used in conjunction with a trigger wheel. It produces a sine wave output with a frequency proportional to speed.
Inert Gas: A non-reactive gas element.
Inertia: The force that holds a body stationary or in uniform motion.
Inertia Reel: Type of seat belt that holds spare webbing on a reel and locks the reel on impact. This is performed by a swinging weighted ball and lever that locks the belt reel ratchet wheel with a pawl.
Inertia Switch: A switch that operates by the inertia (need to stay at a constant speed or state of rest) of a mass. Usually used to cut off supply to a fuel pump in case of a crash.
Infrared: Light that is just below the frequency visible to the human eye.
Infrared Lighting: Infrared light is outside the visible spectrum. When used for lighting, a special detector is also needed.
Infrared Sensor: A sensor that is sensitive and produces a signal in response to infrared light.
Ingestion: Take in by swallowing or absorbing.
Inhalation: Breathing in.
Inhibitor Switch: A simple switch that prevents the operation of a circuit. A good example is the switch in an automatic transmission gearbox that prevents operation of the starter motor when drive or reverse is engaged.
Inhibitors: A chemical that restricts or reduces the chemical reactions. In a cooling system an inhibitor is added to prevent corrosion of the engine from the ethylene glycol content of the antifreeze.
INJ: Injector valve.
Injection: Of fuel by pressure into inlet manifolds (petrol) or combustion chamber (diesel).
Injection Lag: A short time delay between actuation and actual operation of an injector.
Injection Timing: Point within the four-stroke cycle when injection occurs. Similar to ignition timing on petrol engines.
Injector: Control valve and nozzle used to inject and atomise fuel.
Injector lag: A short time delay between actuation and actual operation of an injector.
Injector Nozzle: The tip of a fuel injector, which is drilled to produce a particular spray pattern.
Injector Pulse Width: When viewed on an oscilloscope, the horizontal width of the trace. This represents the open time of the injector.
Injector Pump: Fuel pump that produces the timed high pressure pulses for the injection and timing of fuel delivery on a diesel engine.
Inlet Manifold: Ducting that connects the carburettor/fuel injection components to the inlet ports in the cylinder head.
Inlet Ports: The way in to the engine for fuel/air mixture.
Inlet Valve: Valve in the inlet port that allows air or air/fuel mixture into an engine.
Inline Pump: Type of diesel fuel injection pump with the pump elements in line.
Inner Races: The inside rings of ball or roller bearings.
Inner Tube: The separate sealed air tube on a tyre that is required with certain types of tyre and wheel rim.
Inner Wing: Metal panel structure under the bonnet forming part of the wing.
Input: Power or data that goes into a mechanical unit or electronic control module.
Input Shaft: Shaft that takes drive from the engine into the gearbox.
Insert (Valve Seat): A steel insert fitted in aluminium and some iron cylinder heads to form a durable seating for the inlet and exhaust valves.
Instrument Lights: Illumination for instruments such as the speedometer.
Instrument Panel: The panel in a vehicle fascia that holds the instruments and warning lights. Also dash panel and dashboard.
Insulated Circuit: A vehicle wiring system that does not use the body and chassis as a ground to form a return electrical circuit to the battery and alternator. A separate insulated set of cables connects all components to complete the circuits. Used in vehicles where there is a high fire risk. (Fuel tankers).
Insulator: Restricts the flow of electricity or heat through the material.
Intake Manifold: See inlet manifold.
Intake Stroke: Alternative term for the induction stroke. First stroke of four stroke cycle when air and fuel enter the engine as the piston moves down the cylinder.
Integral Body Construction: Modern light vehicle body and chassis construction method which has no separate chassis. The strength is built in by the use of stressed and reinforced panels.
Integrated Circuit (IC): An electronic device consisting of transistors, diodes and other components in a single unit and usually having a specific function.
Intercooler: An air to air radiator type heat exchanger fitted after a turbocharger in the air intake ducting to cool the intake air before it enters the engine.
Interference Fit: The relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is less than the outer dimension of the inner component.
Interior Lights: Lights inside a vehicle for illumination purposes.
Interleaf Friction: Friction between spring leaves that produces a damping effect.
Interlock: Part of a manual gearbox selector mechanism that prevents the engagement of two gears at the same time.
Intermediate Gear: Any gear in a transmission gearbox other than top and bottom or reverse.
Intermediate Shaft: A shaft between the input and output shafts, usually as part of a gearbox.
Internal Combustion: Engine where fuel is burnt inside cylinders.
Internal Customer: One inside of an organisation.
Internal Damping: A feature of some suspension components where friction tends to reduce oscillations.
Internal Resistance: Describes the resistance of a component that is the combination of all its internal parts. Even a battery has some resistance inside it.
Internal Splines: Splines (teeth) inside a shaft or tube.
Internal Taper: A hole that narrows.
Internal Windings: Windings inside a component.
Ion: An atom with positive or negative charge due to gain or loss of an electron.
Irradiation Treatment: A process where something is acted upon by radiation from a radioactive substance - it is used to make some foodstuffs last longer - but is a contentious issue!
IS: Inertia Switch.
ISC: Idle Speed Control. This term is usually used when a stepper motor or solenoid is used for idle speed increases during engine warm-up and when ancillary systems are in use.
Iso-octane: A fuel used in research tests as a comparison when determining the octane rating of fuels. Octane value of 100.