Engine

Engine immobilisers

An engine immobiliser, as the name suggests, is a security system designed to prevent the engine being run long enough for the car to be stolen. They’ve been a requirement for all new cars in Australia since 2001, so it is very likely your vehicle has one fitted.

Most of the systems work with a transponder chip embedded in the key or fob. When the key is turned or the start button pushed, the car’s computer sends a coded signal out. If the chip in the key responds with the correct code then the computer will allow the car to continue running. If the code is wrong, or no code is received, the engine will be cut. On many cars the engine may run for three or four seconds before cutting out. The key has to be coded individually to the car, which makes getting new keys quite a rigmarole that typically needs access to the car and an already coded key. It’s also expensive, so when buying a new car be sure to ask the dealer for an extra spare key as a sweetener.

If your car is pre-2001 and has an aftermarket system fitted, have it checked out by an auto electrician as part of your service routine.

Because immobilisers are so effective, keys are a hot target for thieves. More than 70 per cent of late-model cars thefts use the car’s own keys. Increasingly, homes are being burgled to gain access to car keys, so make sure you have sufficient home security and don’t leave keys lying around.

Stop-start engine technology

Stop-start engine technology is designed to reduce fuel use particularly in heavy traffic where manufacturers claim it is able to improve fuel economy by as much as 10 per cent.

It shuts off the engine when the car comes to a complete stop and starts it again when the brake is released and the accelerator pressed.

If a car with a conventional starting system was continuously started and stopped, it would soon have issues. To make it work reliably, car makers have rethought how the mechanicals are laid out. Items that once needed the engine running in order to operate, such as air-conditioning and gearbox and power steering hydraulics, have been redesigned to use electric motors instead.

Battery charging was a big hurdle – a car that is restarting every few hundred metres in traffic could soon drain the battery. To cope with this, cars with stop-start technology generally have a larger-capacity battery and more sophisticated multi-stage charging systems.

In addition to this, most of these engines are designed so that they start within one turn of the crankshaft. Some have gone even further by making sure they always stop with the pistons in the same place, which means the starter motor isn’t used much at all.

Speedometer

The first speedos were elaborate mechanical devices that used a cable to take information directly from the drive shaft to the speedo display.

Then came electronic speedos, which generate electric pulses with sensors attached to the drive shaft. The pulses travel along wires and are read by electronic counters in the display. The more pulses in a set time, the faster the shaft is rotating, which allows the vehicle’s speed to be calculated.

These speedometers are easier to build into a car and are more accurate. The electronic signal enables the speedo to give a digital reading, though most car companies prefer to use an analogue dial – but these are prone to reading errors.

Improved accuracy

In recent years, speedo accuracy has improved further, using wheel-speed sensors on each wheel averaged out to provide a more accurate display of speed than cars using a single sensor on the drive shaft.

This increased accuracy spurred a tightening of the Australian Design Rules which now prohibit under-reading, and allow over-reading by 10 per cent of actual speed plus 4km/h. This means that if your vehicle’s actual speed is 100km/h, the displayed speed is permitted to be anywhere between 100km/h and 114km/h. Before 2006, speedos were allowed to be out by up to 10 per cent high or low.

Real-world tolerance

This tolerance, particularly the pre-2006 one of 10 per cent plus or minus, has led some to wonder why the road laws don’t allow the same margin of error when it comes to speeding, since we rely on speedometers to stay within the limit. The design rule is a theoretical allowance, not a reflection of the real world. Speedos were always designed to over-read, almost invariably.

Accuracy check

Car manufacturers can check speedo accuracy at the end of the production line by putting the vehicle on a calibrated rolling road device and logging the speedo electronically. It is possible to pay a specialist to do this for you. A rudimentary alternative is to use the speed-check devices on some freeways. Simply sit on a fixed speed when passing them to get a rough idea of how accurate your speedo is.

As modern speedometers are sealed units they are not adjustable. But some factors that affect speedo accuracy, such as worn tyres, can be fixed.

Same rule for trucks

The speedometers in cars and trucks are subject to exactly the same requirements in the Australian Design Rule. Some trucks have a speed limiter, which limits the top vehicle speed as referenced by the number of wheel rotations per kilometre to no more than 100km/h. The speedo itself, however, will not typically be any less or more accurate than a car speedo. If anything, you might expect custom-built trucks to display more variation (within the allowed tolerance) than a mass-produced car.

Tyres

Perhaps no other item on your car is taken for granted as much as the tyres. They are constantly being worked over as we drive but we usually don’t think about them until one goes flat.

The most usual form of tyre neglect is running them at too low a pressure. This causes heavy wear, delivers poor cornering and braking and, worst of all, blowouts, which can be catastrophic.

Beware under-inflation

You might think having a less-inflated tyre means more of it is in contact with the road but actually it’s the reverse. In an under-inflated tyre, the middle section bows up, leaving only the edges touching the road. This concentrates more heat and wear in these areas.

All car makers recommend pressures for the tyres on their cars. These are listed on a little placard usually found inside the driver’s door jamb or the fuel filler cap.

Check tyres regularly

You should get into the habit of checking tyre pressures at least once a month. This is most conveniently done at a service station, but be aware that the gauges at these places can get battered. If the one you use looks a bit worse for wear, go somewhere else or check the pressures against your own gauge (available from auto spares shops).

While checking the tyre pressures, also look for wear or damage. All tyres have inbuilt indicators to show when they are worn too far.

If there is noticeably uneven wear, the wheel may need rebalancing or the steering alignment may be out. Either way, a specialist should check it. If there are splits or damage, it could be time for a new set of tyres.

Wipers and lamps

Rain-sensing wipers

Rain-sensing wipers may seem like arcane magic, but in principle they’re pretty simple.

On most cars the system consists of a bank of infra-red LEDs and a bank of light-measuring devices, mounted near the interior mirror.

The little infra-red LEDs shine constantly, bouncing beams through the glass. The angle the lights are set at brings into play a physics principle called ‘total internal reflection’. Basically, the beam of infrared light bounces off the top surface of the glass and back down to the sensor. When the windscreen is dry, most light is returned back to the sensor.

When water droplets fall on the glass they act like lenses, causing the light that would have been reflected straight back to the sensor when it was dry to be bounced around inside the droplet instead. This causes much less light to be returned to the sensors. The car’s computer interprets this sudden drop in light return as rain and switches on the wipers. The more water on the screen, the less light returned, which triggers faster wiping.

Daytime running lamps

You may have noticed a growing number of cars driving around with what look like a row of fairy lights under the headlamps.

These are daytime running lamps (DRLs), which are now commonplace in Australia. The Australian Design Rules allow car manufacturers to incorporate them into their styling, and they come in all kinds of weird and wonderful configurations, but are usually found as a strip of LEDs under or near the main headlamp cluster. Their position, and the fact they run independently of the headlamp, leads some people to confuse them with fog lamps, but they are very different.

The difference between DRLs and fog or driving lamps is the intensity and direction of the light produced. DRLs are much less intense as they are not designed to illuminate the road, but to make the car visible to others. DRLs must only ever emit white light and have very tight restrictions on maximum output so as not to cause glare.

We are seeing more cars equipped with DRLs because they are now mandatory in Europe, where regulations state that they must be on at any time that the vehicle is running and the main beam, low beam or fog lamps are switched off. The Australian Design Rules allow DRLs but they are optional for vehicles sold in Australia. They may eventually become mandatory.

Submit your questions to RoyalAuto, 550 Princes Hwy, Noble Park North, VIC 3174 or care@racv.com.au.

Windows and handles

Car windows

The glass in your car is a very specialised beast, a world away from the windows in a house. It has to be designed so that in a crash it breaks in a way that’s as safe and predictable as possible.

Not every window in the car has the same kind of glass. Laminated glass, used mainly on the front windscreen, is essentially a sheet of thin stretchy plastic sandwiched between two layers of glass. The idea is that if the glass is cracked the plastic layer will stop bits of glass from flying around dangerously. The glass itself is also treated so that it breaks into small pieces to provide further protection.

The other type is toughened glass, which is normally found on side and rear windows. It has processes applied that make it very strong and resistant to damage. However when it does break it shatters (sometimes quite spectacularly) into tiny pellets which are much safer than the large jagged pieces typical of a normal window breaking.

Door handles

Door handles may seem the most mundane thing on a car, but the enormous changes in designs over the years are down to more than just fashion.

Before the 1970s, handles were similar to those found on doors in buildings or simple push-button affairs. Then came the Australian Design Rules (ADR), which required door latches to have features that prevent the doors from bursting open in the event of a crash. This led to more elaborate mechanisms using rods and levers, usually actuated by flip handles, and these were common for decades.

It was another safety push that coincided with the rise of programs such as ANCAP that led us to the pull-type grab handles we have now. As well as being ergonomically superior and less likely to break fingernails, these handles are designed to reduce the risk of the door opening in a crash, particularly rollovers and side impacts. They’re also favoured by emergency services when it is necessary to extract a vehicle’s occupants.

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