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Tech Tips Time!

More bite-size tips for modifying your car

By Michael Knowling

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This article was first published in 2006.

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The concept of electric supercharging seems to be regaining popularity. There’s a wide range of electric blowers on the market but the majority of these products (especially the cheaper ones) are of limited worth. You can guesstimate the amount of boost you’ll achieve based on the system’s power draw and the size of the switching relays (used for activation) – the smaller the power rating, the weaker the supercharging effect. Some of the cheaper electric superchargers may deliver boost on a small capacity engine but we’ve seen reports that larger capacity engines see next-to-zero benefit. Also, be wary of claimed power gains that include replacing the vehicle’s airbox – the measured gains are largely due to the ‘naturally’ improved induction flow...

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As new car manufacturers tussle for sales, one marketing strategy is to advertise extended service intervals. The result is less time in the workshop and reduced maintenance cost. However, if you buy a car with extended service intervals, it’s important to read the fine print in the service manual before adopting the regular log book schedule. Take the (now superseded) Mitsubishi Magna as an example – its recommended service interval is every 15,000km but read the service manual closely and you’ll find it suggests a 7500km interval in ‘severe’ driving conditions. That’s half the distance between oil changes! If you give your car a bit of stick and use it mainly for short trips, you’d be ill-advised to adhere to the standard service interval...

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Along with monster turbos and intercoolers it’s becoming fashionable to run big brakes on your ride. While big brakes are something we advocate on any truly quick machine there are some pitfalls for buyers. One of the biggest traps is clearance between the new calipers and your existing wheels – sure, 20 inch rims might be able to accommodate the upsized discs but what about making sure the wheel spokes can pass the new calipers? Before handing over any money, we suggest trial fitting the new brakes or, in some instances, the brake manufacturer may be able to supply a wheel clearance template (PBR has ‘Wheelcheck’ templates at But be careful when relying on measurements to check clearance – a millimetre or two can be the difference between success or failure!

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Modifying your car is all about improving efficiency and performance – so why not apply the same approach to car sound amplifiers? Wiring a 4 ohm speaker to each output channel of an amp is ‘the done thing’ – you get the rated power output along with the claimed levels of total harmonic distortion (THD). The only problem is you’ll need to splurge on another amp if you want more power or more speakers. An alternative is to reconfigure the speaker wiring so you extract the most from your existing amp. If you have an amp that’s stable operating down to 2 ohms, you can wire a pair of speakers to run in parallel from each output channel. The reduced impedance makes the amp work harder and, in many instances, output is doubled (check the specifications of your particular amp). That’s free power – the only downside is slightly downgraded THD.

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On a similar note, you should be careful to take steps to avoid interference and unwanted noise when wiring your amplifier. Regardless of whether you’re using RCA or speaker level inputs to the amp, it’s important to keep them as far away as possible from the 12V power feed. If the amp is mounted in the boot, you should route the RCA or speaker level inputs down one side of the vehicle and the power supply line down either the centre or opposite side. Keep them separated and you should enjoy crystal clear sound!

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After you’ve tuned your atmo engine with all the bolt-ons, cam and cylinder head work, you’ll probably be scratching for further mods. At this point, many people opt for individual throttle bodies – a visually impressive but expensive upgrade. But what sort of gains are there? Well, on a modern engine – especially those with a dual-stage intake manifold - it’s likely you’ll find only a modest top-end gain. This typically comes in addition to improved throttle response. So before splurging your cash, it’s a good idea to first measure the restriction through your existing intake manifold/throttle assembly – all you need to do is find out the manifold vacuum with the engine at full power. The higher the vacuum, the greater the restriction and potential for improvement. If there’s enough restriction to justify an all-new short runner induction layout, you should be aware that it’s possible you’ll lose some drivability and torque at some point(s) in the rev range. Invariably, it’s a trade-off...

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Not long ago an AC power supply in your car was an extravagance – but all that’s changed with recent price plunges! A DC to AC inverter can now be bought from about AUD$50 (for a low output version) while a 500W example (as seen here) can be picked up for AUD$160. This is the perfect unit for powering a fridge, in-car PC or a cappuccino pump based intercooler water spray/water injection (see World's Best Intercooler Water Spray, Part 1). The ability to run AC devices opens up a whole new world!

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Wanna give your engine a relatively low cost and low fuss boost? Well, why not consider a NOS ‘Sneaky Pete’ type nitrous system? The Sneaky Pete (as its name implies) is an extremely compact nitrous injection system that has the potential for stealth installation. The supplied bottle takes just 10oz (280g) of nitrous liquid and the system comprises a nitrous only delivery system, which means you’ll need to put more fuel through the injectors while activated. Very sneaky!

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A trick way of adding some extra appeal and safety to your ride is to swap your conventional third brake light to a LED job. LED brake lights not only look cool but enhance safety thanks to their greater intensity and quicker light-up time compared to a filament bulb. Check out the article Hi-Po LED Brakelight Upgrades to find out how your existing third brake light can be upgraded to high intensity LED technology. Alternatively, you can raid the wreckers to find a complete LED brake light – we bought one for just AUD$15!

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If you’re performing a home car alarm installation it’s important to follow a few easy steps to further minimise the risk of theft. The siren should be mounted somewhere that’s difficult for a thief to access, the alarm wiring should be integrated with the factory loom and you should consider how easy it is for a thief to gain access to the battery without lifting the bonnet (some vehicles have holes into the engine bay from the inner guard). Keep these factors in mind and you should keep your car yours!

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