| Car Terms |
| ABS (Anti-lock Braking System)
Prevents wheels from locking under brakes by sensing wheel slip and releasing and reapplying brake pressure appropriately. By avoiding skidding it maintains steering control under maximum braking and also saves on tyre wear by stopping flatspotting. ABS operation is felt as a juddering of the brake pedal. ABS works on any surface. Airbag Concealed sac in hub of steering wheel or dashboard which inflates during a crash. Many cars now have driver and passenger airbags as standard. Frontal airbags are fully effective only in front-on collisions. Side airbags are gradually being introduced. Small children should not be placed in front seats with airbags. Latest models of BMW 3 series and Mercedes S class have as many as eight, with curtain (window) airbags being the newest variety Approach Angle / Departure Angle The angle at which a 4WD can take a steep climb or descent without scraping the front or rear of the vehicle on the ground. BAS (Brake Assist System) Brake assist system applies maximum braking when it senses a panic stop. Bash plate Thick steel plate fitted under components such as engine, transmission and fuel tank. Designed to take hard off-road knocks. Bullbar Replaces front bumper bar. One-piece tubular bar with hoops above to protect headlights, radiator and front panels from damage caused by hitting wildlife. Steel, aluminium or polycarbonate construction. Cabriolet/convertible Interchangeable terms for car (usually a coupe) with a removable or foldable top. Cd Not the sound system, co-efficient of drag - a measure of how quickly the car moves through the air - the smaller the number, the faster. Compliance plate Legally required small metal plate fitted under bonnet containing information such as date car was built. Seek expert advice if you come across a privately imported car without one - it's likely to be worth less money and you may have trouble getting insurance and/or finance. Coupe Two doors only. Departure Angle / Approach Angle The angle at which a 4WD can take a steep climb or descent without scraping the front or rear of the vehicle on the ground. Differential Drives both halfshafts at the same time but allows them to be driven at different speeds, as when turning. DOHC See Twin Cam. Driveshaft Or propshaft, connects the transmission to the differential. Drivetrain / Powertrain The items necessary to transmit power to the wheels: engine, transmission, clutch (on manuals) torque converter (automatics), and driveshafts. In front-wheel drive cars the gearbox and differential are one unit called a transaxle. In rear-wheel drive cars the power has to be transmitted to the driving wheels from the engine at the front down the length of the car to the differential. Electromagnetic clutch Relies on sensors to detect wheelspin on (usually) the rear axle and then electrically engages a clutch to apportion drive to the front axle, providing 4WD. Four-wheel drive Available on an increasing number of passenger cars as well as the traditional off-roaders, the chief advantage of 4WD is added traction (grip) on slippery surfaces. Disadvantages include higher purchase price, increased weight (and consequently higher fuel consumption) and higher repair costs. Freewheeling hubs On a part-time 4WD they allow manual disconnection of the front axle driveshafts at the wheels, saving on wear. Auto freewheeling hubs are the same except they automatically disengage when the vehicle is reversed a few metres. Front-wheel drive Front wheels pull the car along, the rear wheels just go along for the ride. Helps the rear seat and boot space problem in smaller cars, and cars with front-wheel drive have better traction in rain and snow than their rear-driven counterparts. Differences in handling are often in the eye of the beholder (see Understeer and Oversteer). Front-wheel drive is cheaper and more efficient to manufacture because the major mechanicals are packaged at front of car. Four-wheel drive has increasingly become the norm (see Rear-wheel drive). Fuel injection Fuel injection sends fuel to the engine combustion chamber more efficiently than the old fashioned carburettor. Most are electronically controlled; it achieves better fuel economy and reduces fuel emissions. Multipoint injection is favoured for better performance. Full time Full time or constant 4WD sends power to all four wheels all the time, and unlike part-time 4WDs can be safely driven on hard road surfaces. Some have a selectable mechanical centre diff lock so they can deliver torque in a fixed 50:50 split front/rear (like part-time 4WD) for better off-road grip. Some passengers cars (all Subarus, Audi Quattros) are 4WD. Ground clearance The distance between the lowest central part of the car and the ground. GCM (Gross Combination Mass) Definition according to the Department of Transport and Regional Services: value specificed for the vehicle by the manufacturer as being the maximum of the sum of the Gross Vehicle Mass of the drawing vehicle plus the sum of the axle loads of any vehicle capable of being drawn as a trailer. In other words, the Gross Vehicle Weight (loaded) plus Gross Trailer Weight (loaded). Halfshaft Connects the differential to the wheel. Halogen headlamps Give a whiter light than usual incandescent bulbs. Some makes now offer xenon headlamps, also for whiter light. Handling How the car responds to steering. Good handling means stability on rough roads and in cornering (see Suspension, Oversteer and Understeer). Hatchback Whole rear panel (including back window) is hinged and opens. Hatchbacks may have two or four doors. HDC Hill descent control, Land Rover's system to do away with low range gearing for steep off road descents. Using ABS, it applies brake pressure to all four wheels to restrict speed downhill. High range Normal set of gears in a 4WD, used for driving at normal road speeds. Horsepower Metric usage is to express "power" as kilowatts, or kW, rather than the old fashioned hp or bhp (brake horsepower). The more kW, the more power. Also important to the engine's ability to perform is the power:weight ratio. Some engines are best at moderate engine speeds (rpm) while others have to be revved much higher to produce their maximum horsepower. More relevant for day to day driving is torque, or pulling power, and how the car responds at ordinary engine revs (see Torque). Independent suspension (see Suspension) Most modern cars have independent front suspension, in which each wheel operates independently. If one hits a bump it doesn't affect the other. Independent rear suspension (IRS) is not universal on rear-wheel drive cars. In non-IRS cars there's one solid rear axle; if one wheel goes over a rough patch, both are affected. With IRS the car has more composure on rough roads. Kilowatt (see Horsepower) Limited slip differential (LSD) A mechanical version of traction control, limiting wheel spin on an axle in two and four-wheel drives. Lockup torque converter Fuel-saving device on some automatic transmissions. Some power is lost when automatic transmissions transmit their power and a lockup torque converter stops this power loss or slippage. In some cars you can feel it engage and disengage. Long wheelbase (LWB) Some vehicles are offered in long or short wheelbase (SWB) versions. Low profile tyres The tyre's profile is the height of the sidewall compared with the width of the tread, expressed as a percentage. A number of 60 or lower is considered low profile. Some performance tyres are ultra low, eg 45 series. Low profile tyres have better grip on dry roads but a firmer ride because they are stiffer. Very low profile tyres are not suitable for off-road use and they are more likely to puncture. Standard tyres are usually softer and ride more comfortably but have less grip and more flexing in turns and at high speeds. Tread design is important in wet weather grip; most low profile tyres have a high performance tread with open pattern and good wet qualities. The wider the tyre, the more water you have to shift from under the wheels on a wet road. Low range reduction An extra set of gears for slow speed driving in a 4WD (usually only the lowest two ratios are required). Important for steep slippery off-road trails. LWB/LWB Stands for Long WheelBase. Some vehicles, such as the Holden Commodore and Toyota Landcruiser, are built in two or more body lengths. For the Holden, the Commodore is the short wheelbase version, the Caprice - 150mm longer between the front and rear axles (on VX versions) - is called the long wheelbase version. MacPherson struts Modern front suspension system. They support the car's weight and act as shock absorbers. Multivalve engines An alternative to turbocharging to get more power. Some manufacturers add more valves to the traditional two per cylinder to move air and fuel through the engine more quickly. Some cars have multivalves and turbochargers. Neutral handling The car doesn't show much understeer or oversteer. Normally aspirated Engines which are not turbocharged. NVH Noise, vibration and harshness, a term used to describe all the rattles and squeaks sometimes encountered in new cars. Nudge Bar single tubular hoop, usually made from aluminium or steel, fitted to the front of the vehicle, suitable for minor parking bingles. Inadequate for deflecting a big red 'roo. On-demand 4WD Sophisticated part-time system which runs in 2WD until 4WD is required. The system engages 4WD automatically, it has a switch which senses when to 'close' and engage 4WD. The switch is most often a viscous coupling or electromagnetic clutch. Examples: Control Trac (Ford), Real Time (Honda) Syncro (VW), Torque on Demand (Holden), Quadra-Trac, Quadra-Drive (Jeep). Overdrive A fuel-saving device, overdrive is an extra gear on a manual or automatic which makes the engine turn more slowly at higher road speeds. It's called overdrive because the driveshafts are turning faster than the engine. Overhead camshaft The camshaft operates the valves in an engine. In an overhead camshaft (ohc) engine the camshaft is above the cylinders and makes the engine more fuel-efficient than an overhead valve (ohv) engine, in which the camshaft is mounted in the engine block, further away from the valves. Most 4-cylinder cars are ohc. Oversteer Also known as getting loose, oversteer is the tendency of the rear wheels to push out and maybe lose traction during a turn, with the back end sliding out. Most rear-wheel drive cars can be made to oversteer, especially if the surface is slippery. As power is transmitted through the rear wheels they can be made to lose traction by accelerating hard in first or second gear on a wet or loose surface; a front-drive car is safer in this regard because a sliding front is easier to control. Part-time 4WD Allows use of 4WD when you're driving on slippery roads or off-road. Otherwise only 2WD can be used or else transfer case damage occurs. Examples: Command Trac (Jeep), Easy Select (Mitsubishi). Performance How well a car accelerates, handles and stops. Good performance helps when you need to accelerate quickly, eg when merging onto a freeway, for climbing steep hills, for negotiating turns and rough roads with control and stopping safely. Most modern cars have sufficient performance to cope with everyday road conditions in city and country. Powertrain / Drivetrain The items necessary to transmit power to the wheels: engine, transmission, clutch (on manuals) torque converter (automatics), and driveshafts. In front-wheel drive cars the gearbox and differential are one unit called a transaxle. In rear-wheel drive cars the power has to be transmitted to the driving wheels from the engine at the front down the length of the car to the differential. Ramp-over angle angle a 4WD can drive over a mound without scraping underneath. Rear-wheel drive Only the rear wheels are driving the car; they are connected to the engine and transmission by a driveshaft. On a front-engined rear-drive car the driveshaft runs the length of the interior, reducing passenger room. Very few cars are rear-wheel drive these days, exceptions are all BMWs, Mercedes-Benzes (except the A-class), Commodores and Falcons, Lexus models IS200, GS300 sports and LS400. In the US only a very few giant models are rear-wheel drive. Revolutions per minute (rpm) How engine speed is measured; displayed on a tachometer on the instrument panel. The redline on the tachometer shows the maximum rpm, in cars with a rev limiter you can't accelerate past the redline but have to upchange gear. Ride A subjective notion of the car's comfort. A car should remain stable through turns and at high speed but should also absorb the bumps. Some high performance or sports suspensions are so hard the ride is uncomfortable. If the ride is too soft steering response may be compromised. Saloon/sedan Four doors and a boot. Seatbelts Lap-only rear seatbelts are now regarded as inadequate in an accident. Look for cars which have lap-sash seatbelts for all rear seat occupants. Pretensioners tighten during an accident to give added protection. Adjustable seatbelt mountings also provide better comfort. Selectable full-time 4WD A constant 4WD with a front prop shaft which, if desired, can be disconnected to run in two-wheel drive (saving on wear and rolling resistance). Examples: Super Select (Mitsubishi); Selec-Trac (Jeep). Side Steps A bar or board made of steel or alloy which runs along the length of the sill to allow easier entry to the cabin, and in the case of sturdier examples, protect the sills while off-road. Snatch Strap Like a giant elastic band used to 'snatch' a car out of a bog. Steering Power steering is great at low speeds, eg, when parking but too much power assist can reduce important feedback to the driver about what the wheels are doing. Direct steering response means you immediately feel a change in direction when you turn the wheel and whether you've turned too much or too little. SRS Supplementary restraint system (see Airbag). Suspension (see Independent suspension) In general cars with firmer suspension have better handling but suffer a loss of ride quality on rough surfaces. Known as the ride/handling compromise - the sportier the handling, the harder the ride. A few models have adjustable suspension settings for better (softer) ride or better handling. A test drive would indicate whether this feature is important to you. SWB/LWB Stands for Short WheelBase. Some vehicles, such as the Holden Commodore and Toyota Landcruiser, are built in two or more body lengths. For the Holden, the Commodore is the SWB version, the Caprice - 150mm longer between the front and rear axles (on VX versions) - is called the long wheelbase version. Torque Torque is pulling power, or what you feel when you press the accelerator. Measured in Newton metres (Nm). The amount of torque is a good measure of the engine's power for accelerating in normal driving and when towing heavy loads. Engine speed is also a factor. For example an engine which develops good torque at low engine speed can accelerate well from low speeds, tow well and work efficiently with an automatic transmission. An engine which produces its torque at higher engine speeds has to be revved much harder to accelerate well from low speeds and won't pull heavy loads so well. Such an engine is better for manual transmission, which gives more control over engine speed (see Horsepower). Traction control Uses ABS to apply braking force to a slipping wheel, allowing drive to be directed to the wheels with most grip. Transfer case Part of the transmission which channels drive to front and rear axles and may contain the gearset for low range. Turbocharging In which extra air is forced through the turbocharger to increase engine power. Twin cam/dual cam (DOHC) Some overhead camshaft engines have two cams per cylinder bank. Separate camshafts improve engine breathing and allow higher engine speeds, more efficient operation and more power (see overhead camshafts). Understeer Also known as pushing, understeer is prevalent on front-drive cars when driven hard. The front of the car resists turning and wants to go straight. Some cars are designed to understeer because it is thought to be safer and easier to manage for average drivers than oversteer. Viscous coupling Is an enclosed tube connected between transfer case and driveshaft which has viscous fluid within. This fluid heats up when a pair of wheels start to spin and 'locks' the driveshaft, giving 4WD. Wheel articulation Lateral movement of a live axle; for independent suspension this is described as wheel travel. Wind up Eventually happens when a part-time 4WD (or full-time 4WD with centre differential locked) is driven on paved roads, potentially causing much damage to the transfer case. Winch Usually fitted to the front of the vehicle, it is a steel cable tied to a drum that is driven by a powerful electric motor to retrieve a bogged vehicle. The hooked end of the cable is usually attached to a fixed point and the cable reeled in, pulling the vehicle out of its predicament. |