Motoring dictionary

30 September 2009



ABS: ABS stands for Antilock Braking System. ABS simply keeps the cars base brakes from locking up so the vehicle slows down but the driver remains in control. Alot of modern cars are now fitted with anitlock braking systems.



BOOSTER BATTERY: A second battery used in commercial vehicles to give a little more power when starting.



CARBURETTOR: a device for mixing fuel and air for delivery to the engine. Air is drawn through carburettor by vacuum in the intake manifold produced by the engine and mixed with fuel creating a combustible mixture for delivery to the engine.

COMMON RAIL DIESEL ENGINE: refers to a new generation of diesel engines which have fuel delivered under very high pressure by an electric fuel pump to a common fuel supply manifold, or fuel rail as it's often called, for delivery to the fuel-injectors. Older diesels employ a mechanical pump driven off the engine with individual fuel pipes delivering the fuel to each injector. See also: DIESEL ENGINE

COMPRESSION RATIO: the ratio of the volume of the cylinder at the top of the engine's compression stroke to the volume at the start of the compression stoke. A low compression engine is generally considered to be one with a compression ratio below about 8.0: 1, above that an engine is regarded as a high compression engine. High performance engines generally have a higher compression ratio, and diesel engines have a much higher compression ratio than petrol engines, generally around 15 or 16: 1.

CONVERTIBLE: describes a four-seater car with a fold-down soft top. A convertible is not usually considered a sports car.

CROSSOVER VEHICLE: generally used to describe a car which crosses the boundaries dividing traditional car types. Often used to describe a car like the Subaru Outback which is a regular family wagon with the capability to go offroad.

CRUMPLE ZONE: the front section of the body which is designed to absorb the energy generated in a crash by deforming or crumpling so reducing the energy the occupants of the car are exposed to.

CHASSIS: once described the frame on which the car was built, but only heavy duty four-wheel drives have a chassis in the traditional sense and term now encompasses the whole suspension system.



DEPARTURE ANGLES: particularly used on four-wheel drives as a measure of the bank or obstacle the vehicle will clear when driven either forward or backwards. It's the angle described if you run a straight line from the edge of the road wheel to the leading edge of the bumper.

DIESEL ENGINE: a diesel engine doesn't use a spark plug for ignition, it relies on high compression to initiate the combustion process during the compression stroke.

DIRECT INJECTION: where fuel is injected directly into the combustion chamber instead of the intake manifold.

DISC BRAKES: disc brakes were first used on sports cars in the 1950s, but most cars today are fitted with them front and rear. A calliper forces pads lined with friction material against a spinning rotor to generate a braking force. Braking with discs is much more efficient than the older drum brake system.

DRUM BRAKES: first brakes were drums where a set of shoes lined with friction material are forced out to make contact with the internal friction surface of a rotating drum. Drum brakes are mostly used on the rear of some vehicles today.



ELECTRONIC STABILITY CONTROL: an electronic system which monitors the lateral acceleration of the car among other parameters and activates the brakes through the ABS to correct situations it assesses as dangerous, like understeer or oversteer. It's hard to detect the system working.

ELECTRONIC BRAKE FORCE DISTRIBUTION: modulates the pressure in the brake lines to each individual wheel to deliver maximum braking effect to the wheels that need it rather than distributing the braking force equally to all wheels.



FLY-BY-WIRE THROTTLE: most modern cars no longer have a throttle cable, or indeed any physical connection between the throttle pedal and the throttle on the engine. The throttle on today's cars is connected to the car's electronic brain which reads what the driver wants from the position of the accelerator pedal and the rate it is being depressed or released and send the information to the engine throttle.

FOUR-WHEEL DRIVE: traditionally a four-wheel drive vehicle was one where the drive was evenly split between all four wheels via a centrally located transfer case, but today's four-wheel drive can have smart electronic systems can determine wheel slip distribute the drive to the front and rear wheels to achieve optimum grip. See also: FRONT-WHEEL DRIVE, REAR-WHEEL DRIVE, ALL-WHEEL DRIVE

FRONT ENGINE: a car with the engine mounted ahead of the passenger compartment. It's the traditional place to mount the engine and is used by most modern cars. See also: MID ENGINE, REAR ENGINE

FRONT-WHEEL DRIVE: the front wheels not only steer and brake they also provide the drive. Front-wheel drive dates back to the 1930s when Citroen was one of the first to seriously pursue the concept, but it was the Mini that that put it on the map in 1959. Most cars today are front-wheel drive. See also: REAR-WHEEL DRIVE, FOUR-WHEEL DRIVE, ALL-WHEEL DRIVE

FUEL-INJECTION: virtually all petrol engines employ electronic fuel-injection for fuel delivery. Fuel is delivered to the engine under pressure and is then injected in a fine spray into the air flow in the intake manifold near the inlet valve. Fuel-injection is a more efficient way of atomising the fuel for better mixing and better combustion.



GRIP: the force generated between the tyre and the road which gives the car its ability to steer, break, turn and accelerate. Without it you won't get far.

GROUND CLEARANCE: the clearance between the lowest point on the car and the road surface.



HAIRLINE CRACK: A tiny stress crack which forms due to strains in the material or extreme temperature differences; as opposed to crazing, a single crack of this type will often occur alone.



INDEPENDENT REAR SUSPENSION: a system of suspension in which the rear wheels move independently of one another. It results in better handling as the movement of one wheel can't affect the movement of the wheel on the other side of the car. Both Holden and Ford have independent rear suspension.



JACK KNIFE: The action of a vehicle (tractor) with a trailer in which the trailer and the vehicle form a "V" instead of normally being pulled in a straight line. Usually this is the result of a skid in which the trailer swings around dangerously and tries to overtake the cab.



KANGAROOING: A colloquial term for moving forward in a succession of sudden jerks as a result of improper use of the clutch, (a characteristic of beginner drivers or those not used to standard shifting)



LIMITED SLIP DIFFERENTIAL: A differential unit designed to provide superior traction by transferring driving torque, when one wheel is spinning, to the wheel that is not slipping. A cone or clutch disc locks the two independent axle shafts together so that they both turn at the same time. There is a minimal amount of slippage (thus the name limited-slip) to allow for differential action.



MACPHERSON STRUTS: a simple compact front suspension arrangement which was developed by a young American Ford engineer, Earle MacPherson and used for the first time on the British Ford Zephyr in the 1950s. The MacPherson Strut employs a coil spring around a shock absorber unit, sometimes called an insert, to replace the conventional spring and shock absorber units.

MANUAL GEARBOX: one where the driver selects gears.

MID ENGINE: a car with the engine mounted behind the passenger cockpit, but ahead of the rear axle. It is used for better weight distribution between the front and rear axles which aids handling. Mostly employed on sports cars. See also: FRONT ENGINE, REAR ENGINE

MONOCOQUE BODY (unitary body): describes a car's construction which consists of a body shell without a separate chassis. Most cars today use monocoque construction which delivers greater strength and stiffness which in turn improves a car's handling and crashworthiness.



NATURALLY ASPIRATED ENGINE: (normally aspirated engine) an engine that doesn't employ a turbocharger or supercharger to boost intake pressure above atmospheric pressure.

NEUTRAL STEERING: when the front and rear of the car are following the same arc in a curve. It's rare for a car to have neutral steering.



OVERHEAD CAMSHAFT: describes and engine which has camshafts in or above the cylinder head and directly actuate the intake and exhaust valves. Most modern engines are overhead camshaft, some with one are referred to a single overhead camshaft engine (SOHC), those with two are called double overhead camshaft engine (DOHC). A V6 or V8 which has two camshafts per bank of cylinders is generally regarded as a double overhead camshaft engine, but can sometimes be called a quad-cam engine to denote its total of four camshafts.

OVERHEAD VALVE: originally used to describe an engine with the intake and exhaust valves in the cylinder head, ie above the piston, but now that all engines have valves above the piston it specifically refers to a engine with the valves operated by pushrods from a camshaft located in the cylinder block. The old V6 used by Holden until the VZ Commodore was a pushrod engine, as is the current Gen III V8 Holden uses.

OVERSTEER: the opposite to understeer, oversteer is when the car wants to turn more sharply than the driver intends. In an oversteer situation the rear of the car tends to run wider than the front and the tail can swing out. In extreme situations the car can spin. Car Makers don't design oversteer into their cars because it requires quite a bit of experience to control when it occurs. See also: UNDERSTEER



PADDLE SHIFT AUTOMATIC: an automatic transmission which has shift levers or 'paddles' usually mounted behind the steering wheel for selecting gears. One 'paddle' is usually used to select higher gears, the other to select lower gears.

POWER: is the rate of work generated by an engine. It's comes into play at higher engine speeds and is measured in kilowatts (kW).



QUAD-CAM ENGINE: An engine with four camshafts



REAR-WHEEL DRIVE: the traditional way of propulsion was to deliver the drive to the rear wheels, until the advantages of front-wheel drive where the complete drive train is combined in one package at the front of the vehicle which means the drive train intrudes less on the interior space. Today it's the cars with sporty pretensions that retain rear-wheel drive. See also: FRONT-WHEEL DRIVE, FOUR-WHEEL DRIVE, ALL-WHEEL DRIVE

ROADSTER: a term generally used today to describe a two-seater sports car. It once referred to a two-seater car with few frills.



SHOCK ABSORBERS: employed on each wheel to dampen the movement of the wheel as it moves over bumps. Without them the wheel will bounce up and down without control. Car makers calibrate the shock absorber rate according to the sportiness they want in their suspension set-up. See also: ADAPTIVE SHOCK ABSORBERS

SPACESAVER SPARE: a small temporary use tyre manufacturers use because they take up less space in the boot. Should only be used in an emergency and should be replaced as soon as the regular road tyre is repaired or replaced.

SPORTS-SHIFT AUTOMATIC TRANSMISSION: an automatic transmission which has an additional option which allows the driver to select gears by the movement of the gear shift lever. variously called 'Tiptronic', 'Sports Shift', 'Paddle shift' etc.

SUPERCHARGING: similar to turbocharging, but the supercharger is driven by the engine rather than the exhaust gases. There is no delay in response with the supercharger, it responds as soon as the driver presses down on the accelerator, but being driven by the engine it does use up some of the engine's power. Supercharging is preferred for larger engines where the power loss is less critical. See also: TURBOCHARGING



TORQUE: is the turning or twisting force generated by an engine. It's generally what gets a car going and is measured in terms of Newton-metres (Nm). It's generally at its peak in the lower part of the engine's speed range, diminishing as the revs rise.

TRACTION CONTROL: an electronic brain which works in tandem with ABS which detects when one drive wheel is spinning faster than the other/s and sends a signal to the engine to reduce the torque by cutting the ignition.

TRACK: the width between the wheels. The front track can sometimes be different to the rear track.

TURBOCHARGING: the engine's incoming charge of air and fuel is pressurised by an exhaust driven turbine for more efficient filling of the cylinder which produces greater power. The turbocharger is fitted in the exhaust system and is driven by the exhaust gases as they leave the engine. The engine's incoming air is routed through the turbocharger which increases the air pressure for delivery to the engine's intake manifold where it is mixed with fuel delivered by the fuel-injection system. Turbocharging is preferred on small engines because it doesn't use up any of the engine's power, but turbocharged engines can suffer from a delay in power delivery known as turbo lag. See also: SUPERCHARGING

TURBO LAG: the delay in response from and engine after the driver presses down on the accelerator. Because the turbocharger is located in the exhaust system a small amount of time is lost while the exhaust gases flow through the engine and reach the turbocharger, so the engine feels slow in response while the turbo is catching up to the driver's needs.

TYRE INFLATION PRESSURE: the pressure in a tyre. The recommended tyre pressure can be found on a sticker either in the glove box or on the passenger side front door pillar. Can also be found in the owner's manual.

TYRE TREAD: the area of the tyre that makes contact with the road. The tread's function is to remove water from the tyre's contact patch for better grip on the road.

TREAD WEAR INDICATORS: bars running across the tread moulded into the tread grooves that are hidden until the tread wears down to a dangerous level when they're exposed to indicate the tyre is worn out and should be replaced.

TYRE CONTACT PATCH: the area of the tread that is in contact with the road at any one time and generates the grip that allows us to steer, brake, accelerate and drive.



UNDERSTEER: a handling term that describes a situation when the front wheels want to steer a wider arc than the driver intends. The cars feels as though it's running wide. Most cars are set-up to understeer rather than oversteer which is more difficult for drivers to control. See also: OVERSTEER

UTE (utility): unique vehicle created in Australia to describe a work vehicle that combines the comfort of a car with a load bed able to carry cargo or tools. Differs from an American pickup because it is based on a family sedan, not a truck.



VARIABLE VALVE TIMING: describes the system which alters the timing of the opening and closing of the intake and exhaust valves by rotating the camshaft to achieve optimum power and torque from an engine. Car makers use different terms for their own systems, like VVT-I, VTEC etc.



WHEELBASE: the distance between the centre of the front axle or wheels and centre of the rear axle or wheels. Generally the wheelbase is the same on both sides of the car, but occasionally, for a particular reason, a car maker might make it different from one side to the other.



XENON : A colourless, odourless gas used in electric luminescent tubes to provide a bright light; a xenon stroboscope for ignition timing is strong enough to use in daylight.





ZERO-EMISSION VEHICLE: (ZEV) A vehicle which itself produces no emissions, such as electric powered vehicles. The concept does not take into account the fact that electric cars use the electric power of batteries that are normally charged by power supplied by electric power plants (which generally do produce certain emissions).