Australian Car Advice | News Blog

Engine capacity

Engine capacity refers to the volume swept by all the pistons of an engine, within their bores, from the top to the bottom of their travel. Measured in litres, cubic centimetres (cc) here in Australia. Engines with greater capacities are usually more powerful and provide greater torque at lower rpms but also consume more fuel. However there are exceptions, for example a Subaru Impreza WRX with a 2.0 L engine capacity has more power than a Ford Falcon with a 4.0L engine capacity. This is due to the turbocharger found in the Subaru.

Disc brakes

Disc brakes - unlike drum brakes,use a calliper that grips the disc rotor to the wheel to gain friction. They tend to create more heat than drum brakes, but is designed to continue operating effectively in these conditions - and they are also exposed to outside air which helps with cooling. Within the caliper are usually two brake pads, one for either side of the rotor. These pads clamp together when the brake pedal is pressed. This is a similar concept to that of drum brakes but it is far superior not only in performance but also for reliability.

Problems with Disc Brakes

Many things can happen to disc brakes. But the more common problems are warping (caused by extreme heat), scarring (occurs when pads are not changed when due), and cracking (a bit rare - but occurs due to uneven rotor expansion). The easiest way to repair these problems is by machining the discs. However by doing so, you are effectively reducing the life of your brakes and it might just be cheaper just to replace instead of actually spending money on repairs.

Drum brakes

Drunk brakes are generaly found on the rear wheels of older (or cheaper) cars.  They are inferior to disc brakes as heat cannot escape as effectively while heavy braking can also cause the drums to quickly ware out. In drum brakes friction is caused by a set of pads which press against the inner surface of a rotating drum which is connected to a rotating wheel. However they are still in use today as they are cheaper to manufacturer are found on cheaper (Korean) cars sold here in Australia. It is good advice to try to purchase a vehicle with Disc Brakes instead.

A continuously variable (automatic) transmission uses drive belts in order to transmit torque and allows for various stepless ratios. In otherwords there are more gear ratios than your ordinary automatic transmission. One of the more interesting features of the system is that it often emulates the traditional feel of an abrupt gear change, paticularily at low speeds. This is due to the fact that most drivers expect the sudden jerks while a smooth transmission might appear to show a lack of power!

There are many different types of CVTs:

• Variable-diameter pulley (VDP)
• Roller-based CVT also known as Traction CVT, Extroid CVT, or IVT
• Hydrostatic CVT
• Electronically-controlled CVT

Bash plate

The protector plate fitted underneath vital components like your car’s engine, transmission and fuel tank. The Bash plate is generally made from thick steel. The Idea of the bash plate is to take the hard knocks that you might hit on the road.

Anti-lock braking System (ABS)

Anti-lock braking system prevents your car’s brakes from “locking up” and skidding. When the brake pedal is hit with force, short sharp pulsations are felt as the car’s computer system applies and release braking effort. A typical ABS is composed of a central electronic unit (CEU), four speed sensors covering all wheels, and two or more hydraulic valves connected to the brake circuit. The CEU continiously monitors the rotation speed of each wheel to determine if wheels are going to lockup. It can detect this by sensing wheels which are rotating considerably slower than the others. Once it has detected a possible lockup - the CEU moves the valves to help relieve the pressure within the braking circuit, by doing so it helps to reduce the braking force on the targetted wheel. Following that the wheel then turns faster and when it starts turning too fast, the force is reapplied. The ABS system does the prococess repeatedly.

Problems with ABS

The sensors on the wheels might get contaminated by metallic dust. When this condition occurs the sensors become less efficient in picking up problems. In modern ABS systems, two more sensors are added to help:

• wheel angle sensor,
• gyroscopic sensor

The idea behind this is that when the gyroscopic sensor detects that the car’s direction is not the same as what the wheel sensor reports, the ABS software will cut in to brake the necessary wheel in order to help the car go the direction the driver intends.

For more information on how ABS works, click here

Aquaplaning | Hydroplaning

A situation where a tyre loses its grip on a wet surface and “skates”, greatly reducing a driver’s control. Hydroplaning can occur when a combination of speed, tire wear, tire inflation or the depth of water on the pavement causes the tires to lose traction. The happens when a layer of water comes between the road and your car’s tires. This causes the car to lose traction.

Having good quality tyres can help reduce the chance of a skid while going under 50km/hr. However once you go over 50km/hr the chance of a possible traction loss is no longer dependent on the quality of your tyres (Offcourse there are tyres with higher thresholds). Tyre manufacturers are alwayas coming out with newer tyres to combat Hydorplaning

Hydroplaning prevention:

* Check your tyres and tyre inflation

* Reduce your speed in wet conditions

* Drive in the tracks of preceding vehicles

What todo in the event of a hydroplane:

* Go into neutral (on a standard transmission, depress the clutch)

* Grip the steering wheel firmly and steer where you want to go

* Do not brake or accelerate

Airbags

A bag designed to inflate instantly in the event of a collision to stop the driver and the passanger from hitting the dashboard, steering wheel or other parts of the vehicle. Airbags reduce the risk of death from a frontal crash by around 30% Other types of airbags such as side airbags, some of which are designed to protect the head and the chest, head airbags and curtain (window) airbags are becoming increasingly common in most cars in Australia.

Originally when airbags were first introduced many problems were determined with their design. The basic problem was the violent explosion of the airbag, (300km/hr) was not only causing a serious noise but also caused many minor injuries to the drivers hands or wrists. However over time these problems have all been slowly rectified and modern airbag systems are far more efficient.

Hill Descent Control (HDC) as the name suggests is designed to allow drivers to smoothly hill descent in rough terrain without driver intervention, in otherwords the system gives assistant to the car by slowing each wheel individually to insure that the vehicle does not go past the desired speed, th HDC system is generally linked with the ABS system.

Cruise control buttons are generally used to adjust the speed of the vehicle to a desired level. However much like cruise control, driver pressure to the accelerator or brake pedal will override the HDC system, although this is generally vehicle design dependent. The basic idea of Hill Descent Control is to insure drivers can be confident that even the ride down hills with slippery or rough terrain will be controlled and safe.

Originally Introduced on the BMW 7 Series, Automatic Stability Control + Traction (ASC + T) is a BMW only feature which is a suspension control system that help reduce engine output by making sure that the vehicle can move or acceleration can take place, without wheelspin.

This system can kick in regardless of how the car is being driven. If the reduction in acceleration is not enough, each drive wheel is braked individually until both wheels have optimum traction. Braking is under control of the BMW pioneered Anti-lock Braking System (ABS) system.

• If a wheel looks imminent to spin, the wheel brake is applied or the system intervenes to regulate the engine management accordingly so that wheelspin does not occur. By doing so the engine insures that only sufficient throttle is applied to insure lateral stability, even if the driver has his foot down on the accelerator.
• An integrated engine drag torque regulation system helps prevent the engine from blocking if the driver decides to suddenly let go of the accelerator
• The system can be switched off if required

How does it work:

In critical situations on the road, the angle of the throttle butterfly in the ignition system is altered in such away as to allow only the maximum transmissible power to reach the wheels, while Digital Motor Electronics (DME) adjust the ignition time. This results in the drive force being cut back by up to 50 per cent. In addition, ASC+T will also activate the brakes in the rear wheels if necessary, and to varying degrees if frictional coefficients on the road differ.

The ASC+T system knows when stability and traction have to be increased thanks to the ABS sensors, which provide the computer with a steady stream of data on wheel slip for each side of the car, as well as on changing speeds in the drive wheels. If the predetermined limits are exceeded, the control unit will instantly activate the traction system.

All the driver registers of this complex procedure is a decrease in engine torque despite the fact that pressure on the gas pedal may not have changed. Also, a control lamp in the instrument display will come on to indicate that ASC+T is in action and that the driver should adapt to the altered road surface. Source

Benefits of the Automatic Stability Control and Traction (ASC-X):

* Excellent safety on wet road surfaces (rainy, ice, snow, loose gravel)
* System is quick to act and can detect even slight surface changes
* Blocking of wheels no longer occurs occurs when the accelerator is released on a slippery surface