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Dozen Tech Tips

Twelve bite-size technical tips...

By Michael Knowling

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When it comes to car mods with cred, a phat set of wheels and lowered suspension are at the top of the list. Given the significant cost of a quality set of rims and springs, though, who on Earth can afford some exotic kind of tyre to go with it? Tyres only wear out, after all...

This is a sad situation that - although earning unquestionable car park cred - can actually reduce a car's overall level of handling. Sure, the wider lo-pro rubber will probably give more direct steering feel but what happens to suspension travel, camber and toe angles? And how competent are those cheap-o tyres? Hmmm. If you want those trick rims and slammed suspension, we suggest you wait until you can afford to also splurge on some quality tyres and make the appropriate suspension changes. And, please, don't go too low with ride height!

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So you've pulled a heap of extra ponies from your motor, whacked in some serious suspension and brakes and you wanna hit the track for a bit of fun, eh? Sounds good - but be careful. With the aforementioned mods, you'll be able to enter and exit corners much faster than a standard car and, of course, this produces big G-forces. Just imagine what's happening inside the fuel tank - fuel is sloshing all over the place and, often (especially if the tank level is getting low), the fuel pump won't have any fuel near its pick-up. Uh-oh... Inadequate fuel flow at high load combined with mega engine temperatures is a recipe for disaster.

This WRX engine, for example, lost part of an exhaust valve due to a lean-out at high load. Don't let this happen to you - fit a fuel surge tank (or a so-called swirl pot) and make damn sure your engine doesn't starve of fuel.

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Kilograms are a key to performance. Lighter cars can benefit hugely from a weight loss program - merely ripping out all the junk out the boot, globebox and removing the spare tyre strips a good percentage of the overall weight, and provides a very real on-road (or track) acceleration advantage.

This race-ready Daihatsu Mira illustrates the advantage of weight stripping to its fullest. This little beast runs custom carbon fibre panels, is void of hoodlining, rear seat and belts, window winding mechanisms and even runs a lighter weight steering wheel and aluminium valve cover. Of course, much of this is inappropriate for a road car but - for example - its Perspex side rear windows are probably street legal (check your local laws). Note that, in addition to accelerating quicker, a stripped out featherweight car also has the potential to brake and handle more effectively - it's a case of win-win-win!

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Thinking about adding a rear wing to your club racer or fast road car? Want something that'll provide actual downforce, not just improved aesthetics? Well - if you're serious - one of the best approaches is to take some samples of the wing cross-section used in various factory performance cars (such as the Skyline GT-R) and get it replicated by someone experienced in fibreglassing. Most body kit 'glassers will try to sell you an existing off-the-shelf wing, so you might want to try somebody that makes wings for model aircraft - ask around hobby groups and you'll find someone local.

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When fitting a set of whopper stoppers - or even with a completely standard braking system - it's easy to misidentify a drop in high-load brake pad performance when there's simply flex in the brake mounting system. When you jump on the brakes hard, there's an awful lot of force channelled through the pedal box, master cylinder, brake lines and more. On many modern cars - such as the Subaru Impreza WRX - the firewall is said to flex significantly upon hard brake application, causing a portion of brake pedal movement to be effectively wasted. The solution to this particular problem couldn't be simpler - a metal bracket that prevents the snout of the master cylinder being forced forward. Note that these so-called master cylinder braces serve to improve braking feel and control, rather than provide any real improvement in stopping distances - this is limited more by tyre grip, brake pads and the size of the discs.

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And here's something that can dramatically reduce your chance of experiencing engine damage and it won't cost you a cracker. It's called grey matter. There are a few easy ways to maximise the life of your engine and minimise the amount of time spent digging into your pocket and crawling beneath the car with spanner in hand. First, you should always be thinking about thermal dynamics - that means you should never give your car a boot full when it's still cold (and bear in mind that oil temperature takes longer to rise than the indicated coolant temperature) and, conversely, you shouldn't shut the engine off immediately after a thrash. It's all about letting engine parts warm and cool g-r-a-d-u-a-l-l-y. During driving, you should also bear in mind the amount of underbonnet heat soak at any time - in addition to considering ambient temperature and what octane fuel you've got in the tank - and drive accordingly. There's not much sense knowing your top-mount intercooler absorbs heat in stop-go traffic and then proceeding to launch at full boost on a 40-degree Celsius day. Other considerations are: does your car have a chip that advances ignition timing and leans out mixtures? Does your air intake suck hot underbonnet air? What sort of outlet temps do you expect from your turbo or blower? The list goes on and on but, with some careful thought before you follow your instinct to floor it, you can save yourself a lot of grief.

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Like to go for those long arm-out-the-window cruises? Well, here's a way to both look cool (literally), maintain a lower cabin temperature and, importantly, reduce the chance of getting skin cancer on your 'cruising arm'. Window tint not only looks good, it provides real protection against UV and effectively lags heat penetration. In an interview with Richard Hall from Sun-Gard Australia, he said "Laminated glass - as in the windscreen - stops about 92 percent of UV. Combine that with a quality tint film and you can effectively prevent UV coming in at all." If you're in your car a lot, quality window tint makes a lot of sense.

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Whenever you're switching a high-current device - such as a big pair of spotlights, a high-power electric water pump or an auxiliary cooling fan - you must always use a relay. And don't forget to make sure the relay is rated up to the necessary current required by the device you're switching. If you ignore using a relay and simply wire your device straight from an on/off switch, you'll be limiting the amount of power reaching the device and - even worse - you might overload the switch, causing it to melt... As a guide - depending on the size of a given switch - we'd use a relay for any 12-volt device rated at over 5-amps.

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Big turbos - and we mean humungous turbos - are all the rage. If you haven't got a HKS 90/90 or a Garrett GT3000 'charger people reckon you're whimping out. The fact is, though, many of these monster turbo'd cars later revert back to a smaller unit in order to regain some of the lost low-down torque and throttle response. Sure, an oversize turbo is great for attainting some outa-this-world peak power output that'll win dyno competitions, but - on the street - these 'awesome' vehicles are very often left behind by more responsive cars with vastly less outright power. Don't be sucked in by peak power numbers. Ask yourself; do I want a 'dyno queen' or a kick-arse streeter? Often, the hardware used for each application is quite different...

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If you really 'need' a monster turbo it's a good idea to mask its response and low-load deficiencies with a tricked up auto trans and high-rpm stall converter. What - an auto? Yes, yes, we all know 'true' sports cars use a manual cog box, but if you've built one of the aforementioned big turbo monsters, a high-stall torque converter can do wonders. Say your engine doesn't start making any real boost 'till 4500 rpm, you can fit a stall converter that'll allow revs to flare up to whatever rpm you chose - that way you'll climb onto 'torque band' sooner. Such a set-up is not great for circuit work, but it's ideal for straight lining.

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Lightweight pulleys that connect the engine accessories (such as power steering and air conditioning) to the crank pulley are another power-up mod gaining popularity. Be careful of such products, however.

Many lightweight pulleys 'underdrive' the engine accessories, which means - with a different drive ratio - the accessories are spun slower than normal. Depending on the particular drive ratio, this can cause problems if you're loading up the car's electrical system with a massive stereo etcetera. And think about the massive amount of electrical energy - which is derived from the alternator, remember - that's required to spark the air/fuel mix at maximum engine load. Hmmm.

Some of the lightweight pulleys on the market maintain the same drive ratio as the standard pulleys, but these offer less of a performance advantage. With only a few grams saved per pulley, we have to wonder if a lightened flywheel would provide a greater cost-benefit - it's not uncommon to shed kilograms from a lightened flywheel...

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A great deal can be learnt with your engine's fuel injectors set up on a test bench. With the adjustable fuel pressure regulator used in most test benches, you can easily measure injector fuel flow at various pressures and - with a variable pulse width generator - you can alter the injector opening time. These particular 'side feed' injectors - from a MY94 Subaru WRX - are capable of flowing 19 percent more fuel with fuel pressure raised from 3.0 to 4.0 Bar. The fuel spray pattern also widens considerably at the same time. How else could you possibly learn this?

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