Automotive Glossary

A

Axle Ratio - The ratio between the rotation of the drive shaft and the driven wheel.

Alternator - A belt-driven, saucer-sized device which uses the engine's power to generate electrical energy.

B

Boost Pressure - The measurement of the increase above atmospheric pressure produced inside an intake manifold for any super charged engine. Most commonly measured in psi.

Bellhousing - The metal unit behind the engine that holds either the manual clutch assembly or the torque converter of an automatic transmission.

C

CV Joint – Constant Velocity Joint - A joint designed to allow a rotating shaft to transmit power at constant rotational speed, without an appreciable increase in friction.

Camshaft - The opening and closing of the valves in a piston engine is regulated by a camshaft. A camshaft consists of a cylindrical rod running the length of the cylinder bank with a number of cams, or lobes, protruding from it. The lobes push on valve lifters, converting rotary motion into linear motion.

Compression Ratio - The number that can be used to predict the performance of an engine; it measures the degree to which the fuel mixture is compressed before ignition. It is the measure as the difference between the volume of the cylinder, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke. The higher the compression ratio, the more mechanical energy and engine can make from its air/ fuel mix.

Crankshaft Pulley - The visible wheel attached to the front end of the crankshaft. This pulley drives the alternator, as well as other devices, via the drive/fan belt.

Crankcase - Engine's lower portion - where the crankshaft is located.

Cylinder Head - The top "half" of the engine and the part of the engine responsible for the "breathing," the cylinder head sits on top of the engine block, and contains the engine valves, and often the camshafts as well.

Cold Air Intake - A cold air intake is a device used to bring lower temperature air into a car's internal-combustion engine, to increase engine power and efficiency.

D

Differential - A device that allows each of the driving wheels to rotate at different speeds while supplying torque to both. Most commonly used to split torque evenly between wheels, in four-wheel-drives they can be designed to apportion an uneven torque.

Downshifting - Shifting to a lower gear, usually so that the engine can operate in its proper rpm range, or in certain circumstances to slow the vehicle.

Drivetrain - It mainly refers to primary engine and transmission components that make the car "go."

E

F

Flywheel - One of the main components of your clutch assembly, a flywheel is a metal disc that provides "momentum" to move the car.

G

Gasket - Gaskets are everywhere in your vehicle. Your vehicle is composed of thousands of parts, many of which are joined together. Sometimes the seal between these parts--between the cylinder head and the engine block for example, is crucial. In these cases, a gasket is used to help provide a proper seal. These gaskets can be made of paper, cork, rubber, or metal plates.

Gear Ratio - Gear ratios mathematically determine the relationship between your engine and your transmission. Gear ratios are chosen by manufacturers to provide desired performance characteristics like acceleration and fuel efficiency. These do not change unless the gears themselves are physically replaced.

H

Horsepower - Is a unit of power equal to 746 watts.

Hydraulic Roller Lifters - Have a roller placed on the end contacting the camshaft . This is done to reduce friction between the lobe and lifter. They are generally used when special camshafts and high tension valve springs have been installed.

Harmonic Balancer - A harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration and serves as a pulley for drive belts.

I

Intercooler- A heat exchanger that cools the air or intake charge in a forced induction system.

IAC Valve – Idle air control valve.

J

K

Knock Sensor - A sensor which detects engine knock or 'ping' and then transmits a signal to the engine's computer.

L

M

MAF (mass airflow sensor) - A sensor which measures the amount of air entering the engine. It sends its readings to the engine's computer.

Manifold Insulator - Insulators are used to minimize that transfer of heat energy into the under bonnet, which therefore reduces the temperature of the intake manifold.

N

O

Oxygen Sensor - This device measures the oxygen level in the exhaust gases, allowing the engine to adjust the air/fuel mixture accordingly. (also called an “oh-two sensor”)

Overhead Cam - A camshaft "over the head" rather than below the cylinders in the engine block, Overhead cams eliminate the need for pushrods to open and close the valves.

OTR Cold Air Intake – Over the radiator cold air intake.

P

Push Rods - Pushrods are metal rods that go between the camshaft and the rocker arms. The push rods cause the valves to open and close via the rocker arms.

PSI - Per square inch.

PCV Valve - Part of the Positive Crankcase Ventilation system. When this valve is open, it sucks unburned fuel vapour from the crankcase to the intake manifold for a second burning, and helps lower emissions.

Piston - The piston moves up and down in a cylinder compressing the air/fuel mixture over and over again to be ignited for power.

Q

R

RPM - 'Revolutions per Minute' A measurement of how fast your engine--specifically your crankshaft--is spinning.

Rocker Arms - Curved levers which transfer a 'push' from a push rod to a valve stem in order to make the valve open.

Roller Rocker - A roller rocker is a rocker assembly that uses bearings instead of metal sliding on metal.

S

Supercharger - A means of forced induction, i.e., using compressed air to get a higher density of oxygen in the air-fuel mixture. Supercharging utilizes power from the crankshaft to compress air.

Stroker Kit - Is an aftermarket assembly that increases the displacement of a reciprocating engine by increasing the travel of the piston (that is, the piston moves further up and/or down in the cylinder). This is done by using a different crankshaft where the crank pin is moved further away from the centre of the axis of rotation of the crankshaft. While this increases displacement and torque it can potentially lower the limit to which the motor can rev safely compared to the stock configuration.

T

Timing Chain - A timing chain is a metal chain that drives the camshaft by linking it to the crankshaft. It assures that the valves will open and close at the proper time for efficient ignition.

Thermostat - A regulator for automatically regulating temperature by starting or stopping the supply of heat.

Throttle Body - The throttle body is the valve connecting to the intake tube that regulates airflow into the intake manifold, where air is then distributed to the cylinders.

Turbocharger/Turbo -Is a gas compressor that is used for forced-induction of an internal combustion engine. A form of supercharger, the turbocharger increases the density of air entering the engine to create more power. A turbocharger has the compressor powered by a turbine, driven by the engine's own exhaust gases.

TPS – Throttle position switch

U

V

Valve Spring - A small coil spring that closes the valve and keeps the lifter in contact with the camshaft.