Automobile Glossary contains certain annotations in alphabetical order about the very general terms connected with automobiles. This is to facilitate the common, non-technical personnel to become familiar with the parts and functions of the vehicle they use everyday. It is advisable to use them only as guidance. These are not meant for automobile or mechanical engineering students or engineers.
The terms are pertaining to reciprocating internal combustion engine running on petrol or diesel.
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
A
Abampere: The unit of electric current in C.G.S unit. It is equivalent to 10 Amps.
Anti-lock brakes: An electronically controlled system, which senses initial wheel lock-up while applying the brake pedestal and eases the hydraulic pressure at the wheels which are on the verge of skidding.
Accelerator: It is the pedal attached to the carburetor to regulate the supply of fuel to the engine cylinder. More press on the pedestal cause higher fed of the fuel and greater speed of the vehicle.
Ackermann Steering: This is needed while taking a bend. The inside wheel will travel more sharply than the outside wheel. Outside wheel travels more distance than the inner wheel
Active suspension Technology: It provides comfortable ride, ensuring a perfect balance between smoothness and road handling.
Adaptive Cruise Control: By means of a sensor it is able to know the speed of the vehicle ahead and automatically acts on the brakes or engine to stop the vehicle determining the proper distance between the vehicles. In some cases, the vehicle is stopped even without the interference of the driver.
Aerodynamics: It deals with the study of the best shapes which will ensure higher speed and fuel economy. It has control over fuel consumption, noise levels.
Air bag: It is the inflatable bag located in the steering wheel on the driver’s side or dash box or glove box on the passenger side. If at all there is a collision, the bags will automatically inflate preventing the driver from being thrown to the steering wheel or passenger to the windshield.
Air Brake: Air pressure operated mechanical brake acting on a piston to stop the vehicle. This is normally seen in large trucks.
Air Cleaner: It consists of a filter assembly enclosed in a metal or plastic housing located at the intake of air. The function is to prevent dust from entering the engine
Air filter: it is located within the Air cleaner. It is made of pleated paper It should be replaced regularly.
All Terrain Vehicle: It is used in rough surface conditions. It is also known as Off-road vehicle.
All Wheel Drive: It is a type of 4 wheel drive, meant to ensure smooth travel in unfavorable road conditions. It ensures greater control over the vehicle for the driver. The wheel slippage will reduce considerably. AWD divides the engine torque between front and rear wheels automatically as needed. It is applicable only to on road system and not off-road use.
Alternator: It is the source of power for the electrical system of the vehicle. It converts the mechanical energy into Alternating Current electrical energy (AC Current) which is converted into Direct Current by the diode. This current is used for the electrical system of the vehicle and for recharging of the battery.
Ammeter: It is used to measure the current. It indicates whether the electrical system is charging, staying uniform or discharging. The needle will be at the left when the engine is started, goes to the right as the alternator recharges the battery. Soon it will occupy the middle position.
Airflow sensor: It is used to measure the amount of air flowing to the engine. It is located immediately after the air filter. Based on the sensor readings, the computer of the engine determines the actual amount of fuel injected.
Air Shock Absorber: It is rubber bladder filled with air to act as shock absorber. When air pressure increases, vehicle is raised.
Air suspension: Instead of metal spring, air is used for suspension to support the vehicle.
Ampere: It is the unit of current. One amp equals the amount of current produced by a source of one volt acting on a resistance of one ohm.
Anode: It is the positive pole of an electric circuit. Electrons always flow to the Anode.
Anti-lock breaking System: It ensures stability during breaking. It can also shorten breaking distances. This was originally developed by Bosch and Mercedes Benz.
Automatic Climate Control: The air-conditioned is made to start and stop automatically maintaining the desired temperature of the driver or passenger inside.
Automatic Distance control: It is a combination of Cruse Control and a radar based speed control system. It allows maintaining a constant distance with another vehicle in front irrespective of the action of the driver in front.
B
Ball joint is a part of the front wheel suspension. It helps to hold the front wheels in position. There may be a couple of ball joints for each front wheel.
It is a joint between any two parts allowing movement in any direction between them. It is mainly needed in the suspension system and steering linkage of the vehicle. It ensures smooth rotation. It is dangerous to drive the vehicle with a worn out ball joint because the driver will lose control over the vehicle.
Battery is the electric storage container of DC voltage. It is fundamentally required to start the engine of the vehicle, after which the alternator takes over to supply power to the electrical systems. The alternator is responsible for restoring the battery charge.
Normally, the battery consists of six cells each of two volts connected in series, giving a total of 12 volts DC. The positive and negative terminals of the battery are known as Anodes and Cathodes respectively. Dilute Sulphuric Acid constitute the fluid in the battery or the electrolyte. When a resistance or circuit is connected between the positive and negative battery terminals, chemical reaction takes place as a result of the interaction between the plates and the electrolyte, allowing the current to pass through the resistance.
The battery takes care of the electrical requirement of starting, ignition, lighting, indicating lamp s etc.
Battery Charger is an electrical device used for restoring the original charge or voltage of the battery.
Bearings enable prevention of wear tear between a rotating part and fixed part. Normally they are of two types – bush bearing and ball bearing.
Belt drive enables transmition of rotary motion from a primary unit to a secondary unit with the help of one or more leather or rubber belts and pulleys.
Blower is a fan run by an electric motor. Usually, it is a part of the Air-conditioning system of the vehicle.
Brake caliper is a device shaped like the letter ‘C’ used with the disc brakes. As the driver presses the brake pedestal, the caliper forces the pads against the rotor causing the retardation or stoppage of the vehicle.
Brake discs or brake rotors are circular plates that rotate along with the wheel. When the brake is applied, the caliper presses against the discs stopping the vehicle.
Brake drums contain brake shoes which press against the drum, when the break is applied, stopping or slowing the vehicle.
Brake fluid is a special fluid meant specifically for the brakes used in the hydraulic braking system.
Brake horse power is the actual or net horse power the vehicle can deliver. The British
Brake horse power is 0.98 of metric horsepower.
Brake lines are the tubes that carry the brake fluid among various parts of the brake system.
Brake linings are the heat resistant material of high friction located in the brake shoes.
Brake master cylinder is the main component of the braking system. It takes the pressure applied on the brake pedestal and transmits equally to the four brakes of the vehicle.
Brake pads are located inside the calipers. They create the friction when pressed against the rotor. When it is said that the disc brakes are replaced it only means that the pads are replaced.
Brake Pedal is located at the left of the accelerator pedal. When it is pressed the speed is lowered or the vehicle retardates. When it is pressed the maximum, that is when the brake is applied, the brake shoes press against the brake drum of the wheel causing friction resulting in the motion or kinetic energy to reduce to zero.
Brake system: When the brake pedal is pushed, the pressure created, which is considerably increased by the brake booster. It is then distributed evenly by the brake master cylinder and sent to the brake lines of the wheel with the help of the brake fluid. At the wheel, the pressure causes the caliper in the vehicle with disc brakes to close, causing the pads to act on the brake rotor. The friction developed causes the car to slow down or stop.
In the case of drum brake system the brake shoes placed inside the brake drum press against the drum when the brake pedal is pushed.
Bore is the diameter of the engine cylinder in centimeters or inches
Bottle Jack enables the lifting of the vehicle just sufficient to replace the wheels.
Bumper protects the vehicle frame or body from collision.
Bushing is a rubber, plastic or any such material that fits between two components protecting them from wear and tear or damage.
C
Caliper is within the disc brake and holds the disc pad in position. It helps in pressing the pads against the disc to retard or stop the vehicle. In general, it contains two brake pads and one piston. It is the hydraulic pressure acting on the piston that forces the pads against the brake rotor.
Camshaft is a rotating shaft consisting of a series of cam lobes operating the valve mechanism. It is driven by gears, by sprockets and chain or belt.
Cam lobes are bumps on the cam that activate the lifters which enable closing and opening of the valves while cam rotates along with the distribution shaft.
Carburetor is a device in which the fuel mixes with correct quantity of air drawn from outside through a filter, and vaporizes as needed by the engine. The vapor mixture is allowed to enter the combustion chamber through the inlet valve.
Catalytic converter in the exhaust system is a device which reduces the concentration of exhaust gases and makes it less harmful.
Chain Drive is just like belt drive. It enables the driving of a shaft by another shaft with the help of toothed wheels on either shaft and connected by a suitable chain.
Chassis is the structural framework of the vehicle including the engine, suspension, brakes, chain drive etc. It is an integral part of the body.
Choke supplies rich fuel to the carbureted engine to enable the starting of the engine when it is cold. It controls the intake of air to the carburetor.
Cluster panel is the reverse side of the instrument panel in the dashboard. It contains the electronic and electrical circuits.
Clutch enables the engagement of transmission gears. That means the vehicle will be stationary even while the engine is running. By applying pressure on the clutch pedestal, the clutch is engaged either mechanically hydraulically.
Combustion is the burning of fuel-air mixture in the combustion chamber.
Combustion Chamber is the space between the topmost point of the cylinder and the pace when the piston is at the top dead center during the compression stroke. It is here that the air-fuel mixture starts to burn due to ignition by the spark plug. The volume of the chamber is measured in cubic centimeters.
Compression causes reduction in volume. Combustion is made more effective by compression. It increases engine efficiency.
Compression ratio is the ratio of the volume of the cylinder when the piston is at the bottom dead center to the volume when the piston is at the top dead center.
Connecting rod connects the piston to the crankshaft. It enables the conversion of reciprocating (up and down) motion of the piston into rotary motion of the crankshaft.
Coolant is antifreeze and is a chemical liquid that helps to prevent the freezing of the vapor mixture at extreme low climatic conditions. It also helps in the lubrication of the water pump. The coolant should have 20% to 60% of concentration. It is poisonous.
Cooling fan is generally used to draw cool air from the atmosphere and force it on a hot object or surface, for example, the radiator.
Cooling system is designed to prevent over heating of the engine. Once the engine temperature rises to the operating temperature, the thermostat closes the circuit to operate the pump which circulates the coolant through the engine block and the radiator.
Crankcase is the lower part of the engine block where the crankshaft rotates. It contains oil for the engine.
Crankshaft is the main shaft of the engine to which the connecting rod is attached. It is responsible for delivering the rotary motion. It is generally connected to the flywheel.
Cylinder is the diametrical chamber in the block in which the piston moves up and down. It is in the cylinder that combustion takes place. The cylinder is also known as bore or barrel.
Cylinder Block is the basic framework to which other engine parts are attached. It includes the upper part of the crankcase and the engine cylinders.
Cylinder Head is the upper part of the cylinder block consisting of spark plugs and valves. It is the top of the combustion chamber.
D
Dashboard of the car is the location just behind the windshield. It accommodates instruments, accessory controls, glove box etc. It also contains various gauges. The controls for the head lights, windshield wipers, signals, air conditioner, cassette player etc are placed in the dashboard.
Diesel engine has higher compression ratio. It is of greater efficiency and torque than similar petrol engines. As a result there is better fuel economy and towing performance. It does not require a spark plug or carburetor. However there are glow plugs to pre-heat the cool cylinders to facilitate easy starts. When the engine starts, combustion occurs as the diesel in the cylinder is heated due to the compression.
Differential is the gear assembly connected to the drive shaft which allows the left and right wheels to rotate at varying speeds as the vehicle takes a turn. The exterior wheel has to spin faster to allow for the larger distance it has to cover.
Dipstick is a metal stick with markings needed to check the level of engine oil, transmission fluid, power steering fluid etc.
Disc brake or caliper disc brake consists of a rotor that rotates at the same speed as the wheel, overlapped by a caliper. Disc brake is considered to be better than a drum brake.
Displacement is the total volume of air or air-fuel mixture entering the cylinders during one cycle. It is equal to:
Square of bore x stroke X number of pistons x 0.785, expressed in cubic centimeters or liters.
Distributor is a part of the ignition system. It is driven by the camshaft which provides high voltage to the camshaft in the correct sequence. It distributes proper voltage to each spark plug in the proper sequence. The task is accomplished electronically at present.
Drive shaft transmits power from transmission to differential in a rear drive power train.
Drive train is the path from the engine to the drive wheels. The power transmitting parts like clutch, transmission arrangement, driveshaft, differential, the axle which accommodates the drive wheels etc are all part of the drive train.
Drum brake is a type of brake in which the hydraulic pressure causes the curved brake shoes to hit against the inner walls of a metal drum of each wheel.
Dual Overhead Camshaft (DOHC) engine has two camshafts in each cylinder head, one for actuating the inlet valves and the other for actuating the exhaust valves. As the camshafts are directly on the valves, there is no need of pushrods and rocker arms. This will allow the better build up of the revolutions per minute in quick time.
Dynamometer measures the power of the internal combustion engine.
Dynamic seal prevents the passage of fluid between two moving parts.
Dynamic voltage is the voltage at the source when the circuit is in operation.
E
Electronic Control Module (ECM) is the computer which interprets the electrical signals of the sensors for actuating the engine parts and processes to ensure maximum performance of the engine.
In other words, ECM is the brain behind the engine control system, which with the information received from the sensors ensures proper and efficient operation of the engine.
Electrical System consists of the alternator or generator or dynamo, condenser, coil, distributor, spark plugs etc and their associated wiring.
In the electric-ignition internal combustion engine, the electricity produced by the generator is converted into sparks of high voltage for the spark plug.
Electric Motor converts electrical energy into motion. Originally there were only starter motors and windshield motors. Currently there are small motors for operating the windows, mirrors, seat adjustments, central locking etc.
Electrolyte is a solution of dilute Sulphuric acid which accommodates the negative and positive terminals of the automotive batteries.
Electronic Climate Control regulates the temperature and humidity conditions within the cabin.
Electronic Fuel Injection System consists of an electronic control unit the purpose of which is to regulate the flow of fuel at the appropriate time.
Electronic Ignition System consists of electronic devices to turn on and off the supply of primary current.
Engine Oil is used to lubricate the moving parts of the engine. It reduces the accumulation and formation of rust and corrosion.
Engine Size is the engine displacement given in liters or cubic centimeters (cc).
Engine Thermostat actuates the engine cooling system after sensing the engine coolant temperature.
Emissions are the exhaust vapors discharged into the atmosphere. A catalytic converter in the exhaust circuit reduces the emission.
In Internal Combustion Engine the fuel is burnt within the engine. The automobile engines belong to this category. In the engine the energy of the fuel is converted into mechanical energy or energy of motion
Ethyl Alcohol is a normal vehicle fuel.
Exhaust System includes catalytic converter, silencers or mufflers and piping.
The burned gases escape to the atmosphere through this.
Exhaust Gas Recirculation (EGR) System allows a small amount of exhaust vapors to be brought back to the engine and burnt again. The exhaust vapor when combined with the mixture of fresh air and fuel helps in the reduction of combustion temperatures, which in turn, reduces the formation of nitric oxides in the exhaust.
The purpose of it is to reduce the amount of nitrogen oxide in the exhaust system. During combustion, that is, at high temperatures, Nitrogen is generated. EGR directs a part of the exhaust vapors back to the intake manifold, as a result of which, the combustion temperature falls, causing reduction in the amount of nitric oxides in the exhaust system.
Exhaust Manifold collects the foul vapors from the exhaust ports before being transmitted to the catalyst, muffler and exhaust system.
In the External Combustion Engine the fuel burns outside the engine. The steam engine is an example of external combustion engine.
F
Fan Belt transmits power from a pulley attached to the crankshaft to the engine fan, radiator fan etc.
Fan Clutch controls a variable speed fan. It ensures that the fan runs at the appropriate r speed to prevent engine from overheating. The fan speed is reduced or is put off when not needed.
When the temperature of air passing through the radiator fins increases, the clutch automatically starts the fan. When it reduces, the clutch stops the fan.
The clutch also regulates the fan speed as required.
Fire Prevention System blocks fuel delivery to the engine in the case of a collision or accident, thus preventing the risk of fire.
Flywheel is a large metal disc usually of steel attached to the crankshaft. It spins at very high speeds to develop good amount of centrifugal force. The faster it runs, the more kinetic energy it develops. It translates the work of the internal combustion engine into constant rotational motion.
Forging is a heating process which enables conversion of the metal into items of various shapes and thicknesses.
Four Stroke Cycle in an internal combustion engine consists of four strokes –suction or intake stroke, compression stroke, power stroke and exhaust stroke. It is more efficient than the two stroke cycle. Two revolutions will be needed to for one cycle of four strokes.
In Four Wheel Drive the two front wheels are connected to their own axles and differential and the two back wheels are also connected to their own differential and axles. The power is distributed equally to both the front axles and back axles to drive all the four wheels.
In Four Wheel Steering all the wheels turn when the steering wheel is turned. The rear wheels turn to a smaller degree than the front wheels.
Frame or chassis is the rigid structure of the vehicle made out of heavy steel.
In Front Wheel Drive or Front Drive the power is transmitted only to the front wheels which are actually the drive wheels.
The Front Pipe is a part of the exhaust system, connecting the exhaust manifold and silencer.
Fuel is the combustible material used to generate energy. Petrol and Diesel are the common fuel in automobile vehicles.
Fuel Air Mixture consists of vaporized fuel and clean air, which enter the cylinder from carburetor or fuel injector. The mixture is compressed and ignited to generate the power necessary to drive the engine. In general, the mixture is in the ratio of 16 parts of air to one part of fuel.
Fuel Delivery System forms the path of the fuel flow from the fuel tank to the engine. Apart from the fuel tube or fuel line made of rubber hose or plastic, it includes a fuel filter and fuel pump.
Fuel Economy corresponds to the number of KM/liter of Miles/gallon.
Fuel Gauge is located in the dashboard and indicates the quantity of fuel in the tank. If the needle is at the extreme left the fuel tank is empty (E). If it is at the extreme right the fuel is full (F). Normally, the needle stays somewhere in between E and F.
Fuel Injector is an electrically controlled valve which injects the required amount of atomized and pressurized fuel into the combustion compartment at the appropriate time. It is more efficient than the carburetor as the injection process is controlled in a better way.
Fuel Pump operated mechanically or eclectically, pressurizes the fuel system for transfer of fuel from the fuel tank to the engine.
Fuel Tank stores the fuel before being transferred to the engine through the fuel line, which is positioned a few millimeters above the bottom surface of the tank to prevent foreign materials from passing on to the carburetor or fuel injection system. The top of the tank has an airtight lid which is opened for filling the fuel. At the bottom is a drain plug to facilitate draining and cleaning of the talk.
Fuse is a part of the electrical system. It ensures safety of a component or device from damage due to the flow of high current in the circuit due to any reason.
The flywheel stores kinetic energy. It spins at very high speeds. The faster it runs, the more energy it develops. It translates the work of the internal combustion engine into constant rotational motion.
G
Gap is the distance that the spark must cover to travel from a central electrode to the side electrode of a spark plug.
It is also the distance between rotor and the pick up coil in electronic ignition.
Gasket is a thin, soft material made out of asbestos, cardboard or cork. It is placed between two metal surfaces to ensure airtight seal.
Gas Turbine is an internal combustion engine consisting of a rotor attached with blades. The power generated is smooth as there are no reciprocating parts.
Gauge is an instrument consisting of a dial and a moving needle. It displays the engine conditions. A digital gauge does not have dial and needle but has numbers on it.
Gear Oil is a thick lubricant used for differentials and transmissions. It is generally with a number like SAE 80 or so. It contains extreme pressure (EP) additive or something like that. It enables reduction of wear and friction. It is a heat transfer agent and controls corrosion and rust.
Gear refers to the number of revolutions made by the driving gear to that made by the driven gear. The rim of the gear consists of teeth. Transmission of power can be achieved by meshing of the teeth of the driver gear and the driven gear.
Gear Box consists of an input shaft, a number of gears, and an output shaft.
Gear Shift is a floor mounted lever which helps in manual change of gears during transmission.
Gear Wheels consisting of meshing teeth are used to transfer power between shafts in rotation. A change in the speed ratio is achieved with the help of wheels of different diameters. They are usually made of hard steel.
GPH or gallons per hour is generally the flow rate of the fuel pump. The higher the horsepower, higher will be the GPH required.
Governor controls the speed of the vehicle. It ensures that the speed of the vehicle does not go beyond the acceptable limits.
H
Hatchback is a passenger car with a full height door at the back with window. It may also have a folding seat at the back.
Halogen lamp is a powerful, high output white light lamp used as head light.
Head covers the top of the cylinders and pistons. The combustion chamber and valve train are included in it.
Header constitutes equal length of tubes lying separately and side by side.
Headlight is located at the front on either side of the car and is generally of the halogen type to provide very bright light to see the road ahead during dark. It may also consist of a reflector, lens etc.
Heat exchanger allows heat transfer from one medium to another. In the internal combustion engine, the engine coolant which is a circulating fluid flows inside the radiator coils and air flows through the coils to cool the coolant resulting in the rise in temperature of the air.
Horsepower is the unit of output of the engine. It is equal to the power required to lift 33,000 pounds through one foot in one minute.
Hubcap or wheel cover covers the center of the wheel.
Hydraulic is based on the incompressibility of liquids, say oil and water, which when forced through an orifice produces enormous force. The hydraulic clutches and brakes are based on this principle.
Hydraulic assisted brakes function on hydraulic pressure supplied by power steering pump which helps in applying the brakes.
I
Idle mixture is the mixture of air and fuel in the ratio of about 15 to one, before being fed into the engine cylinders.
Ignition is the firing of a spark plug causing ignition of the air/fuel mixture in the combustion chamber.
Ignition coil is a transformer. The primary circuit receives a small voltage from the battery. This voltage is amplified to a very large voltage in the secondary circuit. This high voltage is transmitted to the sparkplug through the distributor.
Ignition system consists of the components which provide spark to ignite the air-fuel mixture during the compression process in the engine.
Impeller is the rotary part of a centrifugal pump. It has vanes which help to convert mechanical energy into fluid energy.
Inertia is the force necessary to prevent a stationary object from moving. It is also the force necessary to keep a moving object to continue with its motion.
In Inline engine the cylinders are positioned in a straight row, whether vertically or slanted. The crankshaft is common for all the pistons.
Intake stroke is also known as suction stroke. As the piston moves down to the bottom of the cylinder, a partial vacuum is created at the top of the cylinder. Atmospheric pressure causes the air-fuel mixture to be fed into the cylinder opening the inlet valve. During this stroke the exhaust valve remains closed.
J
Jack allows lifting a part of the vehicle from the ground to do any repair or change the tire.
Jumper cables are used to connect a dead battery to a live battery to allow transfer of voltage and thereby energize it.
Jam nut is a second nut tightened against a primary nut to prevent it from loosening.
Jig is a fixture for holding a work.
Jumper wire is used to bypass electrical circuits or components while doing a testing.