Automotive Topics

4WD
Abbreviation of Four Wheel Drive.
4WS
Abbreviation of Four Wheel Steering.
Absorbed Glass Mat Battery
A type of lead acid battery where the electrolyte is absorbed in a matrix of glass fibres holding the electrolyte next to the lead plates.
Absorbent Glass Mat Battery
A separator technology used in some sealed lead-acid batteries in which the glass-mat separator absorbs 100% of the electrolyte.
Ackermann Angle
The toe-out or toe-in of a vehicle with Ackermann steering when the wheels are positioned straight ahead.
Ackermann Curve
The graph created by plotting the difference between the real outer wheel turn angle and the ideal angle against all possible wheel positions from extreme right to extreme left turn.
Ackermann Deviation
The difference between the calculated ideal Ackermann angle and the actual outside wheel angle.
Ackermann Steering
A double-pivoting steering system.
Acoustic Pack
Name given to all of the soft absorptive parts used to reduce noise in a vehicle.
Activated Carbon Canister
An automotive filter in which activated carbon is used to trap fuel tank vapours, which have accumulated when the vehicle is not running.
Active Suspension
A suspension that uses sensors to determine conditions and responds to these different conditions by making compensatory adjustments to the suspension.
Adaptive Cruise Control
Control system used to maintain the vehicle speed without the invention of a driver. Maintains vehicle speed and uses radar to maintain a minimum distance to the vehicle ahead.
Adjustable Shock Absorbers
Shocks with adjustable bump and rebound characteristics.
Advanced Technology Partial Zero Emission Vehicles
Vehicles that meet California Air Resources Board′s requirements for SULEV exhaust emissions, zero fuel evaporative emissions, 150,000-mile emissions durability and an extended emission systems warranty, are referred to as AT-PZEVs.
Aerodynamic Drag
Resistance of a vehicle body to motion through the air. A smooth surface has less drag than a rough one.
Aerodynamic Noise
Sound generated by turbulent flow is just as if the field were generated by a distribution of quadrupole sources.
Aerodynamics
Lists all Aerodynamics topics in the Encyclopaedia
Aerodynamics Calculations
Lists all Aerodynamics Calculations in the Encyclopaedia
Aerodynamics Conversions
Lists all Aerodynamics Conversions in the Encyclopaedia
Aftermarket
All products and services used in the repair and maintenance of vehicles after the vehicle has been sold.
Air Cleaner
A filter designed to remove dust and dirt particles from the air.
Air Filter
A device for removing impurities from the air.
Air Scoop
A forward facing aerodynamic device or opening used to duct cool outside air to some part of the vehicle.
Airbag
A bag that is inflated when an impact is detected to restrain a vehicle passenger.
All Electric Range
The distance over a given drive cycle that a hybrid vehicle can travel on electric power only.
All Terrain Vehicle
A vehicle used in rough surface conditions.
Alloy Wheel
A generic term used to describe any non-steel road wheel. The usual alloys are either aluminum or magnesium.
Alternator
An electric generator for producing alternating current.
Anti Dive Suspension
Front suspension kinematic characteristic which reduces the amount of pitch under braking forces.
Anti Lift Suspension
Rear suspension kinematic characteristic which reduces the amount of pitch under braking forces.
Anti Lock Brake System
A system that can modulate the brake pressure under hard braking conditions to avoid a brake locking and resultant skidding.
Anti Squat Suspension
Rear suspension kinematic characteristic which reduces the amount of pitch under acceleration.
Anti-Dive Suspension
The resistance to a vehicle's tendency to dip down in front when the brakes are applied.
Antifreeze
Compounds of glycol or alcohol, that lower the freezing point of cooling water systems.
Anti-Roll Bar
A bar between the two wheels on an axle used to control roll by attempting to keep the two wheels at the same position in bump / rebound.
Anti-Squat
A measure of a vehicle′s resistance to rear suspension squat due to weight transfer during acceleration.
APU
Abbreviation of Auxiliary Power Unit.
Ash Frame
On some old cars the bodywork was built with a wooden frame, normally made from Ash, with panels attached to the wooden frame.
AT-PZEV
Abbreviation for Advanced Technology Partial Zero Emission Vehicles.
Auto-Ignition Temperature
Minimum temperature at which the vapour/air mixture over a liquid spontaneously catches fire.
Automated Manual Transmission
A manual gearbox where the gear changes are decided by a computer, based on input and output torque and speeds, and the gear change is actuated using a servo.
Automatic Transmission Fluid
Fluid for automatic, hydraulic transmissions in motor vehicles.
Automobile
A self-powered vehicle that travels on land typically with three or four wheels and with 2 to 9 seats.
Automotive Battery
A battery designed to start and run automobile.
Automotive Terminal Post
A round post made of lead used on engine starter batteries.
Auxiliary Power Unit
A device that converts high density fuel into electrical power.
AWD
Abbreviation of All Wheel Drive which also means Four Wheel Drive.
B100 Biodiesel
100% biodiesel.
B20 Biodiesel
A blend of biodiesel fuel with petroleum-based diesel where 20% of the volume is biodiesel.
Baffle Plate
A metal plate that acts as a baffle.
Balance Pipe
A pipe connecting two points of a system to even out pressure fluctuations.
Bargeboard
The finish board covering the projecting portion of a gable roof or part of the car body mounted vertically located between the front wheels.
Battery Electric Vehicle
An electric vehicle that is driven by an electric motor with energy stored in a battery.
Berlin Eye
Refers to the eye of a leaf spring when the eye is upturned.
BEV
Abbreviation of Battery Electric Vehicle.
Biodiesel
Diesel fuel derived from renewable lipid feedstocks, such as vegetable oils and animal fats.
Biodiesel B100
100% (neat) biodiesel. The mono alkyl esters of long chain fatty acids derived from renewable lipid feedstocks, such as vegetable oils and animal fats, diesel engines

Biodiesel B20
A blend of biodiesel fuel with petroleum-based diesel where 20% of the volume is biodiesel.
Blueprinted Engine
Ensuring the dimensions of the parts in the engine are more accurate and, therefore, closer to the original engine blueprint values.
Brake Bias
The distribution of braking between front and rear wheels.
Brake Caliper
The disc brake component that straddles the rotor and houses the piston, cylinder and brake pads.
Brake Disc Rotor
The rotating disc attached to the wheel axle and is clamped with brake pads to decelerate the vehicle.
Brake Fade
A reduction in braking performance due to the brakes overheating.
Brake Graunch
The name given to the noise made by the brakes when they are just slipping when starting (or stopping) from rest. The brake graunch is mainly exhibited on the vehicles fitted with automatic transmission, but can also occur on manual vehicles e.g., on a steep hill. It is caused by brake pad stick-slip when static and dynamic friction is very similar. The term 'creep/groan' is also used to describe the brake graunch.
Brake Horse Power
This is the useful power available at the flywheel of an engine.
Brake Judder
Brake judder is the phenomenon where with medium to heavy braking from high speed, severe vibration is felt throughout the whole vehicle. It is often attributed to a mode of vibration in which the front suspension executes a predominantly fore and aft vibration with the two road wheels in-phase with each other. Excitation is often provided by the oscillatory forcing generated when applying the brakes to a brake disk that has disk thickness variation.
Brake Mean Effective Pressure
This is the average effective cylinder pressure that does useful work calculated from the brake horse power.
Brake Pipes
Pipes used to carry hydraulic brake fluid under pressure.
Brake Servo
A device which multiplies the driver′s physical effort in applying the brakes using the engine manifold vacuum.
Brake Specific CO
The ratio of the rate at which carbon monoxide leaves the engine exhaust manifold to the brake horsepower.
Brake Specific Fuel Consumption
The ratio of the engine fuel consumption to the engine power output.
Brake Specific HC
The ratio of the rate at which hydrocarbons leave the engine exhaust manifold to the brake horsepower.
Brake Specific NOx
The ratio of the rate at which oxides of nitrogen leave the engine exhaust manifold to the brake horsepower.
Brake Squeal
High frequency continuous tone when brakes are applied, this may be a single or multiple tones. The sound is generated by vibration on the surface of the disc itself.
Brakes
A device used to reduce the speed of a vehicle or object.
BSCO
Abbreviation of Brake Specific CO.
BSHC
Abbreviation of Brake Specific HC.
BSNO
Abbreviation of Brake Specific NOx.
Bumper
An automobile bumper helps absorb the energy in an impact.
Camber
Generally a curve.
Camber Angle
Wheel angle relative to ground in front/rear view.
Camber Change
The change between the design value and the actual camber at any suspension position.
Camber Gain
The rate of change in camber as the wheel travels from jounce to rebound.
Camber Thrust
If a tyre is cambered left, it will produce a lateral force towards the left known as camber thrust, even when simply rolling in a straight line.
CANbus
A protocol developed by automobile manufacturers enabling a vehicle′s on-board computer diagnostic system to output standardized data streams.
Carburetor
A device through which air and fuel are atomized and drawn into the engine.
Carburetor Choke
A temporary restriction in a carburetor throat that reduces the flow of air and enriches the fuel-air mixture to aid in starting the engine.
Caster Angle
The angle between upper and lower ball joints in side view, about which the wheel turns.
Caster Change
This is the change between design and any suspension position.
Caster Gain
The change in caster as the wheel moves up and down from full jounce to full rebound.
Caster Offset
The side view distance between the point where the steering axis meets the ground and the centre of the tyre contact patch.
Chapman Strut
MacPherson strut used in a rear suspension.
Charge Cooler
A device which cools a gas between the compressive steps of a multiple stage compressor.
Chassis
The mechanical parts of a vehicle attached to a structural frame, including axles, brakes, driveshafts, and suspension components.
CHG
Abbreviation of Compressed Hydrogen Gas.
Clean Diesel
An evolving definition of diesel fuel with lower emission specifications.
Closed-Loop Fuel Control
A mode where input air/fuel ratio to an engine is controlled by using an exhaust oxygen sensor as the input reference.
Clutch
Coupling that connects or disconnects driving and driven parts of a driving mechanism.
Coachwork
The vehicle body - especially the comfort and luxury appointments as distinguished from the operational chassis.
Coil Over Shock
Standard assembly of spring and damper, where spring perches are at each end of damper.
Coil Spring
A steel spiral spring used to isolate a vehicle from the road.
Cold Cranking Amps
The current required by the starter motor to crank an engine in cold weather.
Cold Filter Plugging Point
A measure of the ability of a diesel fuel to operate under cold weather conditions and is defined as the lowest temperature at which diesel fuel will pass through a fine wire mesh screen of the test apparatus.
Compressed Natural Gas
Natural gas compressed to a volume and density that is practical as a portable fuel supply.
Compression Ignition
Ignition of a fuel charge by the heat of the air in a cylinder, generated by compression of the air, as in the diesel engine.
Compression Shackle
A short arm connecting the rear of the leaf spring to the frame which limits travel by compression.
Computer Aided Engineering
A technique for using computers to help with all phases of engineering design work.
Cone Clutch
The friction surfaces are on inner and outer cone surfaces.
Constant Velocity Joint
A special type of shaft coupling that allows the smooth transfer of power from an input shaft to an output shaft at all angles.
Contact Patch
Area of a tyre that actually touches the road.
Control Arms
A part of the suspension system designed to control wheel movement precisely.
Cranking Amps
The current required by the starter motor to crank an engine.
Crumple Zones
Exist at the front and rear of the vehicle to help absorb the impact of a collision.
CV Joint
Abbreviation of Constant Velocity Joint.
Cylinder Head
The detachable part of the top of the cylinder block that seals the cylinder and forms the top of the combustion chamber.
Damper
Device used to reduce unwanted vibrations of a system.
Dependent Suspension
Any suspension scheme using a single axle to connect both wheels, such that movement of one wheel also directly affects the other wheel.
Diesel Engine
An internal-combustion engine in which the fuel is injected into the cylinder near the end of the compression stroke and is ignited by the heat of the compressed air in the cylinder.
Diesel Particulate Filter
A device which physically captures diesel particulates preventing their discharge from the tailpipe.
Differential
Geared device between the driven wheels to allow varying rotational speeds of the wheels around corners.
Diffuser
The divergent section of a duct which slows down airflow to reduce pressure loss.
Disc Brake
A type of brake in which two friction pads grip a steel disc that is attached to the wheel, with one pad on each side.
Disc Clutch
A disc on the end of the input shaft with a friction surface and a disc on the end of the output shaft.
Double-Tube Shock Absorber
An older design of hydraulic shock absorber using two concentric tubes, one serving as the working cylinder, the other as the reservoir.
Downturned Eye
Refers to the eye of a leaf spring when the spring turns down to form the eye.
Drive-By-Wire
Technology that replaces mechanical connections with electrical connections to reduce weight and provide more sophisticated and reliable responsiveness.
Driveline
An assembly of one or more driveshafts with provisions for axial movement, which transmits torque and/or rotary motion at a fixed or varying angular relationship from one shaft to another.
Driveshaft
An assembly of one or two universal joints connected to a solid or tubular shaft member used to transmit rotational power.
Drivetrain
All of a vehicle′s components that create power and transmit it to the wheels, including the engine, transmission, differentials, and any interconnecting shafts.
Drum Brake
A brake that uses an enclosed rotating drum or can and stationary pads.
East-West Engine Layout
Another expression for a Transverse Engine layout.
ECU
Abbreviation of Electronic Control Unit.
EGR
Abbreviation of Exhaust Gas Recirculation.
Electric Vehicle
A vehicle with one or more electric motors for propulsion.
Electronic Control Unit
A generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle.
Engine
A machine which produces power to do work, particularly one that converts heat into mechanical work.
Engine Bay
The enclosure in which an engine is installed in a vehicle.
Engine Configurations
Various configurations of engine have been developed over the years for power, low noise and vibration, economy or weight.
Engine Excitation Mechanisms
The physics behind the vibrations generated by the internal mechanisms of an internal combustion engine.
Engine Oil
Liquid that reduces friction or wear, or both, between the moving parts within an engine; removes heat, particularly from the underside of pistons; and serves as a combustion gas sealant for the piston rings.
Engine Orders
Engine orders are simply the amplitudes of the frequency components which are the multiples of the rotating frequency.
Engine Radiated Noise
Some empirical noise prediction models have been derived from a sample of 1m radiated engine noise measurements.
Engineering Design
Lists all Engineering Design topics in the Encyclopaedia
Equivalence Ratio
Actual air/fuel ratio divided by the air/fuel ratio at stoichiometry.
European Automobile Manufacturers Association
The Association des Constructeurs Européens d’Automobiles and more often referred to by the abbreviation ACEA.
Evaporative Emissions
Hydrocarbon vapours that escape from a fuel storage tank, a vehicle fuel tank or vehicle fuel system.
Exhaust Catalyst Thermal Management
An exhaust catalyst runs at a high temperature internally and has a high surface temperature that also needs to be accounted for when packaging.
Exhaust Gas Oxygen
The concentration of oxygen in the exhaust of an engine is used in closed-loop fuel control systems to indicate rich or lean air fuel ratios.
Exhaust Gas Recirculation
A portion of exhaust is introduced into the intake of an engine primarily for NOx reduction.
Eye Diameter
The inner diameter of the eyelet at each end of a leaf spring.
FCEV
Abbreviation of Fuel Cell Electric Vehicle.
Flexible Fuel Vehicle
A vehicle that can be run on any blend of unleaded gasoline with up to 85 percent ethanol.
Flooded Cell
A design for lead-acid batteries where the electrolyte is an ordinary liquid solution of acid.
Flywheel
The wheel on the end of the crankshaft that gives the crankshaft momentum to carry the pistons through the compression stroke.
Foot Brake
Vehicle brake applied with the foot.
Fossil Fuel
A fuel such as coal, oil or natural gas that was formed through the decomposition of ancient plant and animal life.
Four Wheel Drive
All four wheels are driven by the engine.
Four Wheel Steering
A mechanism that allows the rear wheels to steer along with the front wheels.
Four-Stroke Engine
An engine operating on a cycle which is completed in four strokes, or two revolutions of the crankshaft.
Friction Shock Absorber
A shock absorber in which friction discs are inserted at the point where the two arms are joined, now no longer used in car suspensions.
Front Wheel Drive
A vehicle designed to have power applied to the front wheels.
Fuel Cell
A device that converts the chemical energy obtained from a redox reaction directly into electrical energy.
Fuel Cell Electric Vehicle
An electric vehicle that uses a chemical energy storage that is converted to electrical energy using a fuel cell.
Fuel Consumption
Definitions of fuel consumption calculations.
Fuel Cycle
The processes involved in extracting a fuel in its native form, converting it to a useful product, transporting it to market, and consuming it at its final destination.
Fuel Economy Drive Cycle
A drive cycle for a vehicle used to establish emissions and range amongst other performance metrics.
Fuel Injector
Electro-mechanical device that precisely meters fuel into an internal combustion engine.
Fuel Pressure Regulator
Maintains fuel pressure to fuel injector to help insure proper quantity is delivered to engine.
Fuel Surge
The term used to describe fuel surging away from the pick up in the fuel tank thus momentarily starving the engine of fuel.
Fuel Tank
The container for fuel on a vehicle.
Full Wheel Travel
The wheel is turned as far as possible from full left turn to full right turn, at full jounce and full rebound.
FWD
Front Wheel Drive - a vehicle designed to have power applied to the front wheels.
Gallon
This unit of volume is defined in the British and American system of units. Note 1 UK gallon = 1.2 US gallons.
Gearbox
A mechanical device that provides a torque-speed conversion between an input and output shaft.
Gross Vehicle Weight
The maximum loaded weight, including the vehicle itself, passengers, and cargo, for which a vehicle is designed and as specified by the manufacturer.
Ground Clearance Line
A curved line in the vehicle side view representing a group of planes above which specific vehicle components are to be located.
Handbrake
Vehicle brake that is applied by hand to hold the vehicle when stationary.
HC
Abbreviation of Hydrocarbon.
Headlight
The main light on the front of a vehicle.
Headliner
Fabric or vinyl upholstery on the interior of the roof of a vehicle.
Heating Ventilation and Air Conditioning
Lists all Heating Ventilation and Air Conditioning topics in the Encyclopaedia
Heavy Duty Engine
An engine that is designed to allow operation continuously at or close to its peak output.
HEV
Abbreviation of Hybrid Electric Vehicle.
HFEDS
Abbreviation for Highway Fuel Economy Driving Schedule.
High Performance Vehicle
A vehicle designed with high levels of performance in certain areas. Normally high power engine to give high accleration rates or top speed.
Highway Fuel Economy Driving Schedule
One of the two EPA fuel economy tests, which consists driving routines, or schedules, performed in the laboratory.
Hookes Joint
A universal joint arrangement designed to cancel out the vibrations caused when the joint angle between the two driveshafts is varied while power is applied.
Hotchkiss Suspension
A live-axle rear suspension in which leaf springs handle both the axle′s springing and its location.
Hot-Stuck Piston Ring
A piston ring that is stuck when the piston and ring are at room temperature, and inspection shows that it was stuck during engine operation.
Hybrid Electric Vehicle
A vehicle powered by two or more energy sources, one of which is electricity.
Hybrid Vehicle
A vehicle that combines a conventional propulsion system and a rechargeable energy storage system.
Hydraulically-Assisted Clutch
A clutch operated by hydraulic pressure.
Hydrogen Economy
A scenario where the world uses hydrogen as the primary energy carrier in place of fossil fuels.
Hydrogen Storage
There are types of hydrogen storage: compressed gas, liquid or chemical.
IC Engine
Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the engine rather than outside of the engine.
Ignition Quality
The ability of a fuel to ignite when it is injected into the compressed-air charge in a diesel cylinder quantified by the cetane number.
Inactive Length
The central portion of a leaf spring that is prevented from flexing by the U-plate.
Independent Suspension
A suspension system that allows each wheel on a vehicle to move up and down independently of the other wheels.
Inertia Fuel Shutoff
A switch that shuts off the fuel delivery system when activated by predetermined acceleration.
Inherently Low Emission Vehicle
Any vehicle that is certified to meet transitional low-emission vehicle standards established by the California Air Resources Board and does not emit any evaporative emissions.
Institution of Electrical Engineers
The IEE is an innovative international organisation for electronics, electrical, manufacturing and IT professionals, with specifically tailored products, services and qualifications to meet the needs of today′s technology industry.
Intelligent Transportation System
An advanced technology approach to traffic management.
Intercooler
A device which cools a gas between the compressive steps of a multiple stage compressor.
Internal Combustion Engine
Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the engine rather than outside of the engine.
ITS
Abbreviation of Intelligent Transportation System.
Joint Angle Limits
The limits, set in the input, on the driveline joint angles through the critical range, to control feasible driveline geometry.
Jounce
Wheel travel upward from design load position.
Jounce Stop
A mechanical limit to vertical wheel travel.
Kingpin Angle
The angle of inclination from the vertical to the kingpin axis in the front view.
Kingpin Axis
The axis about which a road wheel is steered.
Kingpin Lower Point
The point of contact when you extend the kingpin axis to the ground.
Kingpin Offset
The offset from the centreline of the shock to the kingpin axis.
Kingpin Upper Point
The anchor point of the top of the shock absorber.
Lever-Type Shock Absorber
A damper operated by a lever arm from a chassis-mounted hydraulic damper unit.
Limited Slip Differential
Differential with mechanism to limit the amount of differential speed between the two outputs.
Liquefied Natural Gas
Natural gas that has been refrigerated to cryonic temperatures where the gas condenses into a liquid.
Liquefied Petroleum Gas
A flammable mixture of hydrocarbon gases used as a fuel, primarily mixes of propane, butane or both.
litres per 100km
Unit of fuel consumption used in the automotive industry.
Load Transfer
The dynamic transferring of vertical load from one tyre to another on a vehicle.
Lockup Torque Converter
A torque converter fitted with a lockup clutch that can be engaged to eliminate the slip between the torque converter′s input and output.
Longitudinal Engine
An engine layout in a vehicle where the axis of the crankshaft lays along the fore-aft or longitudinal axis of the vehicle.
Low Emission Vehicle
A level of standards for tailpipe emissions.
Low Gear
The lowest gear in a transmission, usually called first gear.
Lower control Arm
The lower suspension link between the steering knuckle and the frame. The arm pivots where it attaches at the frame to allow vertical movement of the steering knuckle.
LPG
Abbreviation of Liquefied Petroleum Gas.
L-Post
A style of battery terminal.
MacPherson Strut
Suspension system which uses a lower control arm and a damper/strut which is designed to take bending loads.
Mass Air Flow Sensor
A device mounted in the engines air induction system that provides an electrical signal representing the instantaneous rate of mass air flow.
mile per gallon
Fuel consumption.
Miles Per Gallon Equivalent
Energy content equivalent to that of a gallon of gasoline.
Module
The measurement that architects use to determine the proportions of a structure, for example, the diameter of a column.
Monocoque
A type of construction in which all or most of the stresses are carried by the skin.
Monoside
A single pressed side of a vehicle body.
Monotube Shock Absorber
A common type of shock absorber with the working cylinder and reservoir contained in one tube.
MPGE
Abbreviation of Miles Per Gallon Equivalent.
Multiple Disc Clutch
Multiple plates on input and output shafts are brought together to transmit torque. The multiple plates increases the frictional area.
Natural Gas Vehicle
Vehicles that are powered by compressed or liquefied natural gas.
Naturally Aspirated
An engine that draws air in without the assistance of a supercharger or turbocharger.
NEDC
Abbreviation for New European Driving Cycle.
Neutral Steering
Handling characteristic between understeer and oversteer.
New European Driving Cycle
A European driving cycle designed to assess the emission levels of car engines and fuel economy in passenger cars.
North-South Engine Layout
Another expression for a Longitudinal Engine layout.
Open Differential
Standard differential with no limited slip or torque sensing features, allows unlimited wheelspin.
Open Loop Fuel Control
A mode where engine input air/fuel ratio is controlled by measuring the mass of input air and adding the proper mass of fuel to obtain a desired ratio.
Overdrive
A transmission ratio below 1:1.
Oversteer
The tendency of a vehicle to turn more than the apparent steering angle.
Partial Zero Emission Vehicle
A vehicle that meets SULEV tailpipe emissions and has zero fuel evaporative emissions.
Particulate
Composed of distinct particles.
Passenger Compartment Acoustic Absorption
The noise within a passenger compartment are controlled by a number of parameters, one of those is the acoustic absorption within the compartment.
Petrol
A volatile, flammable liquid mixture of hydrocarbons, obtained from petroleum and used as a fuel for internal-combustion engines.
Petrol Engine
An internal-combustion engine in which the fuel is petrol that is drawn or injected into the cylinder along with air and ignited with an electric spark.
Petroleum
An oily, thick, flammable, usually dark coloured liquid that is a form of bitumen or a mixture of various hydrocarbons, occurring naturally in various parts of the world and often separated by distillation into petrol, naphtha, benzene, kerosene and paraffin.

Petroleum Fuel
Petrol or diesel fuel.
Pitch - Vehicle Dynamics
The motion of a vehicle in which the front moves up and down relative to the static position.
Pitch Sensitivity
The magnitude of aerodynamic downforce can markedly alter with changes to front ground clearance as a result of pitch movements. This can affect the vehicle performance and feel of the vehicle.
PM0.1
Ultrafine particles.
Polar Moment of Inertia
The resulting inertia of mass forward and rearward of the centre of gravity.
Propshaft
A driveshaft on a rear wheel drive vehicle that transfer rotational power from the engine-gearbox at the front to the differential at the rear.
Pushrod
A metal rod that transmits the motion of the camshaft to the valve actuators
Racing Line
An imaginary line around a circuit that provides the quickest lap time.
Radiator
A device that cools the liquid in the cooling system by allowing it to circulate through a series of water channels, which are exposed to air ducts
Radiator Fan
A fan to provide cooling air toward the radiator.
Range Extender
A device that extends the range of an electric vehicle by converting an energy dense fuel into electricity.
Rear Wheel Drive
A vehicle designed to have power applied to the rear wheels.
Rebound
The motion of the suspension as the strut is extending.
Research Octane Number
The octane as tested in a single-cylinder octane test engine operated under less severe operating conditions.
Revolutions per Kilometre
A unit for the number of times a tyre rotates in one kilometre of travel.
Roll Axis
Longitudinal line around which a vehicle rolls (joins front and rear roll centres).
Roll Bar
Abbreviated name for Anti-Roll Bar.
Roll Centre
Invisible moving point around which a vehicle is considered to rotate in a corner.
RON
Abbreviation for Research Octane Number.
RPK
Abbreviation of Revolutions per Kilometre.
Run-Flat Tyre
A tyre which can run for a certain length of time without air in it.
RWD
Rear Wheel Drive - a vehicle designed to have power applied to the rear wheels.
Secondary Ride
A term used to indicate the ride response of a vehicle in the frequency range of 8-20 Hz.
Shock Absorber
A unit that adds damping to the relative motion of two parts.
Shunt
The transient response of the body to changes in the engine mean torque transmitted to the road wheel by the driveshafts.
Single-Tube Shock Absorber
A common type of shock absorber with the working cylinder and reservoir contained in one tube.
Sipes
Narrow slits in the tread blocks that allow the tread block to flex and so increase grip.
Sleeve Valve Engine
In the sleeve valve engine the conventional valve train was replaced by a ported cylinder liner that was then rotated to align with ports in the block so as to achieve the timing for the intake and exhaust strokes for the four-stroke cycle.
Slick Tyre
A tyre that has no tread on it′s surface.
Slip Angle
The difference as an angle between the direction a tyre is travelling in and the direction the wheel is pointing.
Slip the Clutch
To operate the clutch so that it partially disengages, as when keeping up the revs when driving off; causes wear on the clutch.
Snatch
To take up the drive suddenly when the clutch pedal is released.
SOFC
Abbreviation of Solid Oxide Fuel Cell.
Solid Axle
Suspension where left and right wheels are rigidly connected except torsionally.
Solid Brake Disc
A brake disc that is solid metal between its friction surfaces.
Solid Height
The height of a coil spring when it is totally compressed to the pont at which each coil touches the adjacent coil.
Solid Oxide Fuel Cell
A fuel cell that employs a solid, ionically conductive material as electrolyte.
Space Frame
A series of structural members assembled to create a skeletal system that supports the interior systems as well as the exterior skin and driveline components of a vehicle.
Space Saver Tyre
A spare wheel and tyre which is much smaller than the regular tyres and can be used to replace a flat tyre.
Spare Tyre
An extra wheel and tyre assembly which is stored in the vehicle in the event of a flat tyre.
Spare Wheel Well
An indentation in the boot floor that houses the spare wheel in a horizontal position.
Spark Plug
Electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark.
Spark Plug Fouling
A deposit on the electrodes of a spark-plug of essentially non-conducting material that may, but will not necessarily, prevent the plug from operating.
Spark Plug Whiskering
A deposit of conductive material that tends to form a bridge between the spark-plug electrodes or to a ground, thus shorting out the plug.
Specific Fuel Consumption
The amount of fuel needed to provide a given power for a given period.
Spiral Wound Lead Acid Battery
Instead of having the electrodes as flat plates, the electrodes are rolled up in a spiral.
Splayed Springs
Leaf springs that are not parallel to the centreline of the vehicle in the plan view.
Splitter
A generally flat, horizontal, forward-protruding extension to the underbody of a race car.
Spring Top Leaf Thickness
The thickness of the topmost leaf in a multiple-leaf spring.
Sprung Weight
The weight supported by the suspension, including a proportion of the suspension arms.
Steering Angle
The angle the wheels are turned at any instance relative to straight ahead.
Steering Offset
The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the centre of the tyre′s contact patch.
Steering Ratio
The ratio of steering wheel rotation angle to steer angle at the road wheels.
Steering Shimmy
A steering wheel oscillation that often occurs at a certain road speed.
Stopping Distance
The minimum distance for a given speed that a vehicle takes to come to a rest, normally includes driver reaction time and braking distance.
Straight-Line Speed
The highest speed obtainable by a vehicle driving in a straight line.
Sump
The engine oil reservoir.
Super Ultra-Low Emission Vehicle
A level of standards for tailpipe emissions.
Suspension
A system consisting of small particles dispersed in a liquid. The system of springs, links and absorbers that suspends a vehicle above its wheels.
Suspension Bush
Provides compliance and damping between two points of a suspension system.
Synchromesh Gearbox
A gearbox using a device that synchronizes the speeds of gears that are being shifted together.
Telescopic Shock Absorber
A tubular damper operated by rod and piston, either single or twin-tube.
Tension Shackle
A link attached to the rear eye of a leaf spring and to the frame of the vehicle.
Tetraethyl Lead
An octane enhancer.
THC
Abbreviation of Total Hydrocarbons.
Tie Bolt
A fastener which passes through the leaves of a leaf spring, holding it together.
Toe-In
Setting the front wheels to toe in will mean that when driven the wheels will tend to be aligned.
Toe-Out
Setting the front wheels of a front wheel drive car to toe out will mean that when driven the wheels will tend to be aligned.
Torque Converter
A fluid coupling used in automatic transmissions to transmit power from the engine to the wheels.
Torque Converter Lock-up Clutch
An automatically engaged clutch in a lock-up torque converter which prevents slipping losses.
Torque Curve
A graph which shows the engine torque as a function of machine speed.
Torsion Bar
A type of spring that twists as it is compressed or stretched.
Total Hydrocarbons
All of the hydrocarbon emissions from an internal combustion engine.
Traction Control
A means of electronically reducing the power to the driving wheels, to minimise wheel-spin, and maximise traction.
Transaxle
A transmission and differential combined in one integrated assembly.
Transitional Low Emission Vehicle
A vehicle that is certified to meet the TLEV emission standards established by the California Air Resources Board.
Transverse Engine
An engine layout in a vehicle where the crankshaft axis lays across the vehicle.
Tubeless Tyre
A tyre which does not have a separate tube.
Turbo Lag
The delay between opening the throttle and a turbo producing boost.
Turning Circle
The diameter of the circular path created by the wheel furthest from the center of the turn.
Two-Stroke Engine
An internal-combustion engine that has one power stroke per revolution.
Tyre Aspect Ratio
The ratio of section height to section width multiplied by 100.
Tyre Envelope
The surface that fully encloses the tyre in all positions that it can occupy at full jounce and rebound, from extreme left to extreme right turn.
Tyre Pressure
The recommended pressure that the tyre should be run at.
Tyre Rolling Circumference
The effective circumference of a tyre loaded against a surface.
Tyre Rolling Radius
The effective radius of a tyre loaded against a surface.
Tyre Speed Rating
The maximum speed the tyre can be run at.
Tyre Squeal
The noise made by the tyres when experiencing sudden acceleration or braking or when cornering too fast.
Tyre Tread Pattern
The design cut into a tyre surface to improve grip, particularly in wet conditions.
Universal Joint
A mechanical device which transmits torque and/or rotary motion between two shafts that are not in a straight line.
Universal Terminal Post
A style of battery terminal, with a round post similar to the automotive post, but with a threaded stud in the center of the post.
Unladen Weight
The actual weight of a vehicle or combination with no payload.
Unsprung Weight
All parts of the vehicle that are not supported by the suspension system, wheels, tyres, brakes, etc
Upper Control Arm
The control arm that extends downward from the frame of the vehicle to connect with the axle.
V10 Engine
Ten-cylinder engine with the cylinders arranged in two banks of 5 and the shape of a V when looking along the line of the crankshaft.
V16 Engine
Sixteen-cylinder engine with the cylinders arranged in two banks of 8 and the shape of a V when looking along the line of the crankshaft.
V4 Engine
Four-cylinder engine with the cylinders arranged in two banks of 2 and the shape of a V when looking along the line of the crankshaft.
V6 Engine
Six-cylinder engine with the cylinders arranged in two banks of 3 and the shape of a V when looking along the line of the crankshaft.
V8 Engine
Eight-cylinder engine with the cylinders arranged in two banks of 4 and the shape of a V when looking along the line of the crankshaft.
Vacuum Pump
Device used for creating vacuums.
Valve Regulated Lead Acid Battery
A lead acid battery that uses pressure valves that open only under extreme conditions.
Variable Rate Spring
A spring that does not offer uniform resistance to compression.
Vee Engine
One with two banks of in-line cylinders mounted with an angular separation on a common crankcase.
Vehicle
A means of transport, generally meaning an automobile.
Vehicle Acceleration
The rate at which a vehicle accelerates, normally declared as time taken between two speed points.
Vehicle Dynamics
The dynamic behaviour of the vehicle.
Vehicle Emissions
Harmful pollutants to the health and the environment include particulates, hydrocarbons, carbon dioxide, carbon monoxide, ozone, lead, and various oxides of nitrogen.
Vehicle Exterior Noise
Noise produced by a land based vehicle that is radiated to the surrounding environment.
Vehicle Noise
The noise produced by a land based vehicle that is radiated to the surrounding environment (exterior noise) or that is observed by the occupants of the vehicle (interior noise).
Vehicle Performance
This covers a number of aspects including: acceleration, braking performance, top speed, cornering acceleration, …
Vehicle Suspension
The springs, shock absorbers and linkages that suspend a vehicle's frame, body, engine, and drivetrain above its wheels.
V Engine
One with two banks of in-line cylinders mounted with an angular separation on a common crankcase.
Viscosity Index
An arbitrary measure for the change of kinematic viscosity with temperature.
Viscous Coupled Differential
Limited slip device which uses sheared fluid between two plates to limit wheelspin.
VRLA Battery
Abbreviation for Valve Regulated Lead Acid Battery.
Warning Lamp
A small lamp that will light up if there is a problem.
Watts Link
Lateral locating device for a solid axle.
Wet Clutch
A clutch immersed in a cooling lubricating fluid, which also keeps the surfaces clean and gives smoother performance and longer life.
Wheel
The Mesopotamians are credited with the invention of the wheel.
Wheel Balance
The wheel and tyre of a vehicle needs to be balanced so that as they rotate they do not vibrate. Any wheel and tyre assembly vibration can result in a wobbling of the steering wheel or if severe the whole vehicle.
Wheel Bearing
The main wheel bearing that allows the wheel to rotate, supports the vertical load, fore/aft load and side loads generated during cornering.
Wheel Bump
The motion of the suspension as the strut is compressing.
Wheel Droop
Total downward movement of a wheel from a static ride height.
Wheel Hop
The vertical oscillatory movement of a wheel between the road surface and the sprung mass of the vehicle.
Wheel Nut
Fixings that secure the wheel to the wheel hub.
Wheelbase
The distance between the centres of the front and rear wheel axles as viewed from the side of the car.
Winchester Gallon
The US gallon, equivalent to 3.785411784 litres.
Zero Emission Vehicle
A level of standards for tailpipe emissions.
Zero-Offset Steering
A steering system whose geometry has a scrub radius of zero.

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