Terms Starting with V

 
Valence ring-The outer orbit of electrons in an atom.

Valve-A device used to open and close a port to let intake and exhaust gases in and out of the engine.

Valve body-The part of an automatic transmission used to direct the oil flow to different parts of the transmission.  

Valve bounce-When a valve closes because of spring pressure, the valve may bounce when it closes.  This action can damage the seats or break the valve in two.

Valve clearance-The clearance or space between the valve and the rocker arm.  As the parts heat up, the clearance is reduced because of the expansion of parts.  The clearance keeps the valves from remaining open when the engine is hot.

Valve face-The part of a poppet valve that actually touches the seat for sealing in the cylinder head.

Valve float-If a valve spring is not strong enough to close the valve, the valve may float or stay open slightly longer than designed.  This condition will limit the maximum rpm of an engine.

Valve guide-The part in the cylinder head that holds the stem of the valve.

Vapor-A substance in a gaseous state.  Liquids become vapor when they are brought above their boiling point.

Vaporize-The process of passing from a liquid to a gas.  Fuel is vaporized when it is heated.

Vapor lock-Vapor buildup that restricts the flow of gasoline through the fuel system.  Vapor lock occurs from heating the fuel, causing it to turn into a vapor.

Variable resistor-A resistor that is able to change its resistance by moving a lever or handle.  Often, a variable resistor is used to control some electric circuit that needs a variable resistance, such as a variable speed fan motor used for heating the passenger compartment.

Variable valve timing-A mechanical-hydraulic-electrical system able to change the point at which the valve opens and closes by using a computer.

Varnish-A deposit in an engine lubrication system resulting from oxidation of the motor oil.

VAT-A voltage, amperage, tester used for checking the output of a charging system.

V configuration-A style of engine that has two rows of cylinders that are approximately 90 degrees apart and in a V shape.

Vehicle speed sensor-A sensor that measures the speed of the vehicle and used as an input to a computer.

Venturi-A restriction in a tube where air or liquid is flowing.  A Venturi always causes a vacuum to be created at the point of greatest restriction.

Vernier caliper-A measuring tool used to accurately measure length to 0.001 inches.

VIN-The vehicle identification number, located on the left front of the dashboard, which represents various data such as the model of the vehicle, year, body, style, engine type, and serial number.

Viscosity-A fluid property that causes resistance to flow.  The higher the viscosity, the greater the resistance to flow.  The lower the viscosity, the easier for the fluid to flow.

Viscosity index-A term used to measure a fluid’s change of viscosity with a change in temperature.  The higher the viscosity index, the smaller the relative change in viscosity with temperature.

Volatility-The ease with which a fuel is able to ignite.

Voltage-The push or pressure used to move electrons along a wire conductor. 

Voltage drop-Voltage lost at each resistor, usually defined as I x R drop (amperage times resistance).

Volumetric efficiency-A measure of how well air flows in and out of an engine.


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