Automotive Glossary
Automotive Glossary
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VVolts | |
V BATTBattery voltage. | |
V BeltA continuous loop drive belt with a 'vee' section. The sides of the belt grip the side faces of 'vee' pulleys to provide a friction drive method. | |
V PWRPower voltage. | |
V-beltA continuous loop drive belt with a 'vee' section. The sides of the belt grip the side faces of 'vee' pulleys to provide a friction drive method. | |
V.I.NVehicle Identification Number." | |
V(ref)Reference voltage. | |
V5/V5CVehicle log book/registration certificate. Issued by the Driver and Vehicle Licensing Agency. | |
VACVacuum | |
Vacuum AdvanceAutomatic engine ignition timing adjustment using the inlet manifold pressure to sense engine load. The pressure, as a vacuum, is applied to a diaphragm assembly to move the base plate in the ignition distributor. | |
Vacuum Assisted BrakesA brake booster system that uses inlet manifold vacuum in a brake servo unit to increase the driver's braking effort. The vacuum can also be provided from a vacuum pump on diesel engines. | |
Vacuum GaugeAn instrument for measuring pressure (below atmospheric pressure) of a fluid or a gas. | |
Vacuum MotorA motor that is operated by a vacuum such as to move or drive something. | |
Vacuum PipesSee Vacuum Hoses | |
Vacuum PumpTest equipment that can be used to apply a vacuum. | |
Vacuum RegulatorA device that either controls vacuum so a set level or one that uses vacuum to regulate another operation. | |
VAFVane Air Flow Sensor. | |
ValencyTerm describes a material that has a free electron. | |
ValetingThis is the performance of an extremely thorough cleaning, polishing and waxing of an automobile, both inside and out, to produce a showroom-quality result. | |
ValueThe degree of darkness or lightness of a colour. | |
ValveA control device that restricts or cuts off the flow of a liquid or gas. | |
Valve BallA ball used to create a seal inside a valve. | |
Valve BlockCollection of valves in one unit that operate a common system (automatic transmission for example). | |
Valve BounceBounce of a valve in its seat when closing. Usually occurs as a result of the engine speed being too high or the valve spring losing tension through age or deterioration. | |
Valve Gear (Train)The mechanism from a cam to a valve in an engine that transmits the movement of the cam to open the valve. | |
Valve GuideThe tube or sleeve in the cylinder head that locates a valve centrally in its seat. The valve slides in the guide during opening and closing. | |
Valve HeadThe top or disc end of a valve that seals the gases in the cylinder head. | |
Valve LagThe term applied to valves which remain open after the piston has passed tdc or bdc at the end of a stroke in the four stroke cycle. | |
Valve LeadThe term applied to valves which open before the piston has passed tdc or bdc at the beginning of a stroke in the four stroke cycle. | |
Valve LifterCam follower or tappet. | |
Valve MarginThe thickness of the valve head between the valve face and the head surface. | |
Valve NeedleThe control pin in, for example, a fuel injector. The needle works against an accurately shaped component to control flow. | |
Valve OverlapThe term used to describe the angle of crankshaft rotation when the inlet and exhaust valves are both open. | |
Valve SeatThe bevelled surface annular face in the cylinder head that closes each port and into which a valve seats and seals the port. | |
Valve Seat InsertA steel insert fitted in aluminium and some iron cylinder heads to form a durable seating for the inlet and exhaust valves. | |
Valve SpringThe spring that closes and holds closed the valve. It fits around the valve stem above the guide and between the cylinder head and valve spring retainer. | |
Valve StemThe shaft of a valve. | |
VaneA flat component used as part of a pump that moves a liquid or fluid. | |
Vane PumpA type of positive displacement pump formed by an eccentric rotor driving two or more vanes fitted inside a housing. The eccentricity of the rotor and vanes forms the pumping chambers of the vane pump. | |
VaporSee Vapour. | |
VaporisationFuel that is broken down to very fine particles and distributed into the intake air stream of an engine. | |
VaporizationFuel that is broken down to very fine particles and distributed into the intake air stream of an engine. | |
VapourMinute airborne droplets of a liquid or liquid that has been heated to a gas state. | |
Vapour LockVapour formation in a fuel line caused by heat. The effect is similar to an air lock and acts to prevent fuel delivery. To clear the vapour lock the fuel line must be bled or allowed to cool. | |
VAPSVariable assist power steering | |
Variable Choke CarburettorA carburettor with a variable diameter venturi (choke tube). The variable diameter is obtained by inlet manifold vacuum being applied to one side of a diaphragm or piston and atmospheric pressure to the other side. This arrangement produces a constant depression and relatively accurate fuel metering. | |
Variable ResistorA resistor that can have its value changed manually. | |
Variable VenturiA venturi (narrowing of a tube) that can be changed. Usually refers to a carburettor. See also Variable Venturi Carburettor. | |
Variable Venturi CarburettorSee Variable Choke Carburettor. | |
VarnishA burnt gum deposit from petrol that forms in the inlet tract of carburettors and on piston skirts. | |
VATVane Air Temperature Sensor. | |
VCCViscous Converter Clutch | |
VCMVehicle control module. An electronic control unit that controls a wide range (or all) of the vehicle functions. | |
VDCVolts Direct Current | |
Vee BeltDrive belt made with a V section. | |
VehicleAnother name for the binder, into which all of the other ingredients of a paint mixture are added. This includes pigment solvents, diluents, resins, driers, etc. | |
Veiling (cobwebbing)The formation of a web or strings in a paint as it emerges from a spray gun, usually caused by too high viscosity, low atomising air pressure or a combination of both. | |
VelocitySpeed in a designated direction. | |
Vent PipesPipes used to ventilate something such as a fuel tank or crankcase. | |
VentilatedAir circulating freely in room, disc, etc. | |
VenturiConvergent-divergent nozzle which accelerates air flow and lowers static pressure in gases or vapours flowing through it. In a carburettor the venturi provides the depression in the air flow pressure causing the fuel to be drawn from its float chamber into the air stream. | |
VerbalAny form of communication that uses words, i.e. speaking and writing in the form of letters, newspapers, emails etc. | |
VibrationHigh frequency oscillating wave producing sound or pulsating feeling. | |
Vibration DamperA device, usually fitted to a rotating shaft (crankshaft) that dampens the vibrations produced in the shaft by rotary imbalance or a pulsed drive. | |
VINVehicle Identification Number | |
VIN (Vehicle Identification Number)Unique code assigned to each vehicle by its manufacturer to identify the model, year, production sequence and other vehicle specific information. | |
VinylA class of monomers which can be combined to form vinyl polymers. Widely used to make chemically resistant finishes, tough plastic trim and other vehicle components. | |
Viscomatic LockA drive mechanism that uses fluid to create a lock at a certain speed. | |
ViscometerA viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. | |
ViscosityThe flow rate of a liquid. The addition of solvents and/or diluents will reduce the viscosity or fluidity of the paint. Paint viscosity must be carefully adjusted and controlled to allow proper atomisation and flow-out. | |
Viscosity cupA precision device used to measure the viscosity of a liquid by timing how long it takes the liquid to drain out of the cup in a continuous stream. The standard Viscosity cup in use in the UK paint industry is known as a BS B4 or DIN 4 cup, which has a 4mm orifice for the paint to flow through. | |
Viscosity IndexA measure of the change in the flow rate (viscosity) of a liquid with temperature rise. The higher the viscosity index the smaller is the change in viscosity. | |
Viscous CouplingA drive coupling that uses a fluid to transmit drive. Also sometimes a fluid coupling. | |
VOC ContentThe measure of volatile organic compounds (VOC's) in solvent-borne paints. Usually measured as the weight in kilos of non-exempt solvent per tonne of paint. | |
VolatileReadily changes to vapour or gas at ambient temperatures. | |
VolatilityThe tendency of a liquid to evaporate. Liquids with high boiling points have low volatility and vice-versa. Volatility affects flash-off time and fire hazard consideration. | |
VoltageElectromotive force expressed in volts. Potential difference. | |
Voltage DropThe voltage that is lost when an electrical current passes through a resistance. | |
Voltage RegulatorAn electrical or electronic device to maintain a generator output within a narrow voltage range. | |
Voltage StabiliserA mechanical (bimetal) or electronic device used to maintain voltage at a set level. In instrument systems this prevents readings changing as system voltage changes. | |
Voltage StabilizerA mechanical (bimetal) or electronic device used to maintain voltage at a set level. In instrument systems this prevents readings changing as system voltage changes. | |
VoltmeterInstrument for measuring electric potential. Can usually be set to read AC or DC on different ranges. | |
VoltsUnit of electromotive force. Potential difference. | |
VolumeThe capacity of a space as a numerical calculation. | |
Volume SolidsThe percentage, on a volume basis, of the non-volatile material in a paint. | |
Volumetric EfficiencyThe ratio of the actual amount (mass) of air entering an engine cylinder against the actual swept volume of the cylinder. | |
Volumetric SensingA system used by alarms to sense movement inside the vehicle. | |
VOSAThe Vehicle and Operator Service Agency | |
VRVoltage Regulator | |
VSVehicle Sensor | |
VSIVehicle Specific Information, provided to NTs to aid the correct assessment of a vehicle under test. | |
VSSVehicle Speed Sensor. | |
VT20An MOT Test Certificate which includes the English/Welsh dual language version (VT20W). | |
VT20 ETAn MOT Test Certificate for issue during a period of Emergency Testing. | |
VT30A notice of refusal of a MOT Test Certificate including the Welsh counterpart (VT30W). | |
VT32An Advisory Notice – issued to advise of items of concern identified during the test that do not justify the refusal of a test certificate. | |
VT40MOT Inspection Check List used by a NT during a test for vehicles other than motor bicycles (see VT40M). | |
VT40MMotor bicycle MOT Inspection Check List used by a NT during a test. | |
VTSVehicle Test Station | |
VTS DeviceThe Computer device installed at each VTS on which each test must be registered, from which MOT documentation is produced and to perform certain administrative functions. | |
VulcanisationThe treatment of rubber and rubber compounds to make them capable of being moulded. Also used to refer to the sealing of a tyre or tube repair with an adhesive and heat process. | |
VVCVariable Valve Control | |
VVTVariable Valve Timing | |