Motoring acronyms

There was a time, not so long ago, when a new car owner had to consult the manual only when they needed to change a rear light bulb or some other awkward minor task.

Nowadays the owner's manual stretches to three or four times the number of pages and failure to read anything less than cover-to-cover will mean the owner is probably not using half the bells and whistles fitted to their particular model.

Or worse still, is not taking advantage of some safety systems fitted.

And motoring journalists are probably not helping them a great deal, especially older drivers, when referring to ABS, EBD, ESP, CVT, EGR, TC, not to mention piezzo injectors, variable nozzle turbochargers and lambda sensors.

Many owners are not technically minded and just want the car to accelerate well either with a turbocharger, variable valve timing or variable intake volume.

But there are some abbreviations and acronyms that all owners should understand especially when a warning lights up on the dashboard showing a flashing “ABS”.

To help, Carsguide has come up with a list of the more common terms and abbreviations seen in road test and specification panels.

ABS: Anti lock brake system

A computer uses speed sensors on each wheel and applies and releases brakes on any particular wheel or wheels depending on the grip and whether or not that wheel, or wheels, is skidding when the brakes are applied.

ABC: Active body control

The suspension alters its characteristics to keep body roll to a minimum under hard cornering.

ACC: Active cruise control

A speed maintenance system in which the driver sets the speed he/she requires. The computer then opens the throttle to reach the set speed or applies the brakes to reduce speed to the set value. Some systems also detect other vehicles and slow the active cruise-controlled car to ensure it does not run into the back of the vehicle in front.

A PILLAR

The piece of steel on the side of the windscreen going from bonnet line to roof.

AWD: All wheel drive

A term being used by mainly car makers to show their vehicle distributes power to all four wheels, not just the front or rear pair.

CNG: Compressed natural gas

Gas emanating from the Earth (usually methane and CO2) compressed and used as a fuel for spark-ignition engines.

B PILLAR

The piece of steel running from floor to roof between the front and back doors.

C PILLAR

The piece of steel next to the rear window running from boot line to roof.

CETANE RATING

This is the “opposite” of octane rating and is used to measure a diesel fuel's ability to burn when injected into air hot from being squeezed or compressed in a very high compression diesel engine.

CRUISE CONTROL

A speed maintenance system where the computer opens the throttle sufficiently for the car to reach a predetermined speed. Any time the car's speed drops below that predetermined level the computer opens the throttle to reach it again. Normal cruise control does not stop the vehicle exceeding the set speed on steep downhill runs.

CV Joint: Constant velocity joint

A coupling that allows drive shafts not in the same plane to spin at the same speeds. A CV joint is commonly the coupling between the wheel and the drive shaft from the gearbox on front-wheel-drive cars. It is also known as a universal, the term commonly used to refer to the same device on a rear-wheel-drive car's driveshaft.

CVT: Constantly variable transmission

Instead of interchangeable toothed steel gears and shafts, the gearbox uses belts and pulleys that change their circumference to alter the ratio of the engine revolutions to the driveshaft revolutions. The ratio between the engine revs and the drive shaft revs then becomes constantly variable.

DOHC: Double over head camshafts

Camshafts that run across the top of the engine, one for the exhaust valves and one for the inlet valves that work either directly on the valves or on the valves through rocker arms.

EBD: Electronic brake force distribution

The computer, via wheel sensors, figures out which wheel can take most braking effort without locking up. If the inside wheels were in gravel and the outside wheels on dry tarmac it would probably direct most of the braking force to the outside wheels on the tarmac.

EFI: Electronic fuel injection

Instead of using a carburettor, fuel is introduced to the engine via injectors either in the inlet manifold just before the inlet valve or directly into the combustion chamber. The timing of the injection and the amount of fuel injected are controlled electronically.

EGR: Exhaust gas recirculation

Primarily a diesel engine device, cooled exhaust gas is channelled into the intake manifold and goes through the engine again. This cuts down on harmful gases created in the engine's combustion process.

ESP: Electronic stability program

The computer uses the same wheel sensors as ABS along with some others, and then cuts engine power and applies the brakes selectively in an effort to overcome understeer or oversteer.

GPS: Global positioning system (satellite navigation)

The GPS computer uses signals from three satellites to determine where the car is and can issue instructions on how to get to another location.

DSR: Down hill speed regulation

This is mainly on 4WDs. The computer applies the brakes selectively to the four wheels to keep speed below a certain level but without letting any one wheel skid or lock up.

HSA: Hill start assist

The computer keeps the brakes applied even when the driver has taken their foot off the brake pedal. It can operate for a time, say two seconds, or until the vehicle starts to move forward. This helps to stop rolling back on hills before starting off.

BA: Brake assist

The computer applies extra pressure to the brake lines having sensed there is an emergency situation. This means the brakes work more quickly and powerfully even if the driver fails to put in maximum effort on the brake pedal.

LAMBDA PROBE

This is a device set into an engine exhaust pipe to measure the amount of oxygen in the exhaust gas. Too much oxygen means the engine's fuel injection system is running the engine too lean which uses less fuel but creates more harmful exhaust emissions. Too little oxygen means the engine is running rich, good for power but also poor for emissions and fuel economy.

LPG: Liquified petroleum gas

Gases found with crude oil, mainly butane and propane but including others, which when highly compressed turn into a liquid which is then used as fuel in spark ignition engines.

LSD: Limited slip differential

A differential which allows one of the two driven wheels to turn only a limited amount before its stationary opposite number is also forced to turn. In a limited slip diff, both wheels will eventually turn or spin regardless of the amount of traction each wheel can achieve. In a non-limited slip diff it is possible for just one of the two wheels to spin continuously while the opposite number remains stationary. Limited slip diffs are found more commonly on high-performance cars where they give more precise control of the car.

MPI/MPFI: Multi point injection/multi point fuel injection

Used to describe a fuel rationing system where the fuel is injected individually into each inlet port or cylinder rather than one constant injection into a common manifold linking all cylinders.

OCTANE

Petrol in Australia is commonly rated 91, 95, and 98 octane. This is not a measure of the energy in a litre of petrol but is a measure of the petrol's resistance to exploding (detonating or knocking and undesirable) rather than burning (desirable) in an engine. A high-octane petrol means it resists exploding when compressed in an engine much better than a low octane petrol. But a car with a high compression ratio makes more power than a car with a low compression engine so 98 octane fuel is needed for high performance, high compression engines if they are to give their best.

OVERSTEER

The back of the vehicle slides out when cornering.

PIEZO INJECTOR

A (relatively) new type of fuel injector for engines which is almost infinitely controllable, meaning the engine management computer can vary a

fuel injection cycle not only to deliver a certain amount of fuel but can spread it out over a number of “squirts” or injections. This is especially helpful for diesel engines which benefit in less noise, less emissions and more power if the fuel injection is spread over a number of mini injections.

UNDERSTEER

The front wheels are turned left or right but the vehicle goes straight ahead, “scrubbing” or “pushing” the front tyres across the pavement.

TC/TCS: Traction control system

The computer applies the brakes to individual wheels, and/or throttles back the engine, to overcome spinning wheels on slick surfaces. In 4WD vehicles it may distribute the power in varying amounts to front or back wheels or even individual wheels.

TORQUE

Torque is a twisting force. It is the force created by a spinning engine that tries to keep the engine spinning when other forces are trying to slow it down. Torque is the force that governs how quickly cars accelerate.

HORSEPOWER/KILOWATTS:

Horsepower is a measurement of the engine's ability to do work. It takes a certain amount of horsepower to move a car weighing a certain amount at a certain speed. One horsepower is the equivalent of 550 foot-pounds per second, or the energy required to lift one pound 550 feet every second or 550lbs one foot every second. In the metric system one horsepower is equivalent to 745 watts or 0.745 of a kilowatt.

TURBO LAG

The time between the accelerator being pushed and the exhaust gases building up enough volume and velocity to effectively spin the turbine in the turbocharger. The time taken between pushing on the accelerator and having the engine produce effective torque or power.

VVT: Variable valve timing

The opening and closing of the inlet and exhaust valves in relation to the position of the piston in the bore, can be changed while the engine is running. “Mild” valve timing means good cylinder filling with air and fuel at low engine revs and good smooth power while “wild” valve timing at high engine revs means more power as the engine reaches its maximum speed.

Variable nozzle turbochargers

Turbochargers rely on certain pressures, and amounts, of exhaust gas to work efficiently. Variable nozzle turbos can work efficiently over a much greater range of pressure and quantity than fixed nozzle turbos. A variable nozzle turbo will therefore have much less turbo lag and will start forcing air into the engine (and consequently more fuel, which equals power) at much lower engine revolutions than a fixed nozzle turbo.