FAQ

4WD:

Four Wheel Drive. As a matter of English, 4WD should mean that there are four driving wheels regardless of how many wheels there are in total, but invariably at means 4×4.

4x4:

Four wheels (4x4) and all of them driven (4x4), 4WD.

6x4:

Six wheels, four of them driven, similarly 4x2, 6x2, 8x4 etc..

6x6:

Six wheels, all of them driven, similarly 4x4, 8x8 etc..

ABS:

Anti blockier system, anti lock brake system. Jensen was an early adopter.

AWD:

All wheel drive, so strictly speaking n wheels and and all of them driven, e.g., 4x4, 6x6, 8x8 etc.. However, Subaru and other makers of soft-roaders attempted to appropriate the term for 4x4 cars with limited capabilities off bitumen.

B20 diesel:

A blend of 20% biodiesel and 80% petroleum based diesel, available in WA as of 2006.

B5 diesel:

A blend of 5% biodiesel and 95% petroleum based diesel, available in WA as of 2006.

CNG:

Compressed Natural Gas, sometimes used as a vehicle fuel, is mostly methane, CH₄.

CO₂:

Carbon (C), di(2) - oxide (O), a greenhouse gas. The main products of combustion of petrol and diesel are water (H₂O) and CO₂.

Diff-lock:

A device to lock a differential so that both outputs must rotate at the same speed -- useful in slippery conditions (mud, snow) where loss of grip by just one driven wheel can otherwise cause complete loss of propulsion. Often featured in 4WDs and in sports and racing cars.

Differential:

One input, two outputs, allows left and right driven wheels to rotate at different speeds while turning corners (sometimes also front and rear wheels in full-time 4WD).

DOHC:

Double OverHead Cam shafts. Where an engine has two overhead cam shafts -- see OHC. NB. In an engine with two or more cylinder banks (V6, V8, etc.), this means two cam-shafts per bank.

E10:

A blend of 10% ethanol and 90% petrol. Also see ethanol.

E5 petrol:

A blend of 5% ethanol and 95% petrol. Also see ethanol.

ESC (also known as ESP):

Electronic Stability Control. Electronics sense which direction the vehicle is moving (from inertial sensors), versus which way it should be moving (from steering angle) and vary the brake force at each wheel to attempt to correct any discrepancy, for example, due to a skid.

Ethanol:

C₂H₅(OH), the happy part of wine and beer. Ethanol may also be blended with petrol, e.g., 5% in E5, 10% in E10. Ethanol-petrol blends started to become available in Australia ~2007. NB. ethanol may damage engines that are not designed to use it. See [fcai]['08].

Full-time 4WD:

Where all four wheels are driven all of the time, even on bitumen. If fully mechanical, this requires three differentials in a 4 wheeled vehicle -- one in each axle, and one (the "centre diff.") between the axles. Also see part-time 4WD.

FWD:

Front Wheel Drive, almost always, but also FWD.

Gallon:

Unit of volume. Imperial gallon (UK) = 4.546 litres. US gallon = 231 inch³ (=3×7×11) = 3.785 litres.

GT:

Gran Turismo, now much over-used but supposedly indicating a fast car for relaxed, long distance driving, and one not necessarily as agile as a sports car.

HDC:

Hill Descent Control, electronic gizmos apply brakes selectively to keep the wheels rotating, slowly, while descending steep hills on rough tracks. The device, and term, first seems to have been used by LandRover on Discoveries and Range Rovers.

Hybrid:

A vehicle powered by two forms of engine, separately or together, as of the '00s generally a petrol or diesel internal combustion engine, and an electric motor with a battery pack. Typically the battery can be charged by (i) regenerative braking and (ii) the internal combustion engine. Also see Plugin Hybrid.

Intercooler:

A heat-exchanger (radiator), either air-air or air-water, to cool hot air being fed from a turbo-charger (or less commonly a supercharger) into an engine -- compressing air increases its temperature and cooling it down again further increases its density.

Jeep:

Originally a light 4x4 vehicle of World War Two vintage.

Knocking:

Premature or incorrect ignition of the air-fuel mixture in a petrol engine which causes shock waves and can be heard as a "knock". It can cause major engine damage.

Land-Rover:

4x4 maker based in the UK.

LPG:

Liquified Petroleum Gas, especially as in a vehicle fuel. It generally consists of propane and/or butane.

LSD:

Limited Slip Differential.

Mile:

Unit of length. 1 mile = 5,280 feet = 1760 yards = 1.60934 km.

MON:

Octane rating, motor method; see Octane rating.

mpg:

Miles per gallon, that is the number of miles travelled per gallon of fuel consumed. (Beware, the US gallon is smaller than the Imperial gallon).

Octane:

Octane, C₈H₁₈, has various isomers. The octane rating 100 is defined by the isomer 2,2,4-trimethylpentane (iso-octane), CH₃C(CH₃)₂CH₂CH(CH₃)₂. The octane rating zero is defined by straight-chain normal heptane, n-heptane, C₇H₁₆. (It is possible for a fuel to have an octane rating >100.)

Octane rating, octane number:

Indicates the resistance to detonation of petrol used in a spark-ignition engine. It is the proportion of 2,2,4-trimethylpentane in a blend with n-heptane that has the same knock properties, in a special test engine, as the fuel being rated. (The research method (RON) employs a lightly loaded test engine, the motor method (MON) an engine under load.) All other things being equal, an engine with a higher compression-ratio will require the use of a higher octane fuel. Also see knocking, octane, and RON.

OHC:

OverHead Cam shaft, where the cam shaft that operates the engine valve gear is in the cylinder head, above the cylinders. NB. In an engine with two or more cylinder banks (V6, V8, etc.), this means an overhead cam-shaft per bank. Also see DOHC.

Part-time 4WD:

Where a vehicle is normally two wheel drive (usually the rear wheels), but drive can be engaged to the other two wheels, typically by means of a mechanical dog clutch. Also see full-time 4WD.

Parking ticket:

A form of voluntary taxation.

Plugin Hybrid:

A hybrid vehicle where the battery pack (often of high capacity) can be charged from the mains electricity supply, e.g., at home, overnight.

PULP:

Premium UnLeaded Petrol, introduced in Australia some time after 1985; it has a RON of 98 and is more expensive than ULP. Some imported cars must use PULP to operate optimally and/or to avoid knocking. There is no power or efficiency gain from using PULP in an engine that is correctly designed to run on the cheaper ULP.

RON:

Research Octane Number, as determined in a lightly loaded running test engine (research method). Also see knocking, octane, and octane rating.

Speeding ticket:

Another form of voluntary taxation.

Supercharger:

An engine-driven air-pump to force more air into an internal combustion engine, where it can burn more fuel, and produce more power (possibly at lower efficiency). Also see turbo-charger.

SUV:

Sports Utility Vehicle, an American term for 4WDs, particularly with light to moderate capabilities off bitumen.

Traction-Control:

Electronics detect wheel spin and apply wheel brakes selectively, and/or lower engine power, to prevent it.

Turbo-charger:

An air-pump driven by exhaust-gases, via a turbine, to force more air into an internal combustion engine, where it can burn more fuel, and produce more power. Because it captures what would otherwise be waste energy lost out of the exhaust, a well-designed turbo-charger may increase an engine's efficiency overall. Also see intercooler and supercharger.

ULP:

UnLeaded Petrol, introduced in Australia ~1985; it has a RON from 91 to 93. Prior to the introduction of ULP, petrol had a small amount of Lead added in the form of tetra-ethyl lead, (CH₃CH₂)₄Pb, to increase the octane rating. Lead had the side-effect of protecting non-hardened valve seats from rapid wear, but is toxic, and would poison catalytic converters designed to reduce pollutants in exhaust gases. Also see PULP.

XWD:

Cross-Wheel-Drive -- Saab nonsense for "active-on-demand ... engagement of the rear wheels to optimize traction at take-off; & an electronically controlled rear limited-slip differential (eLSD)," i.e., light duty 4x4 / 4WD / AWD, c2008.