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Tech Tips

DIY tips for better outcomes

by Julian Edgar

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This article was first published in 2011.

From zero cost rubber sheet to salvaging HID headlights, from a very low cost digital/analog intake air temp display to forced air cooling of under-bonnet electronics.... more tech tips for you!

Zero Cost Rubber Sheet

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The other day I was getting a set of tyres fitted at the local truck tyre dealer. I wasn’t driving a truck; it was just that the nearest distributor for the brand of tyres I wanted was primarily a truck dealer. While the tyres were being put on I wandered around the place, only to see a large bin containing an enormous inner tube – probably from the rear tyre of a tractor or mine tipper. When I paid the tyre bill I asked if I could have the discarded inner tube – and the answer was yes.

So why did I – and why would you – want an old inner tube? The answer is that such a tube contains an enormous amount of thin sheet rubber. Armed with a pair of sharp scissors, you can simply cut out the amount you want.

So far I have used the rubber sheet to make rubber washers (cutting them out with a leather punch), to prevent two surfaces rubbing together, as a gasket to make a box water-tight, and as a rubber vibration absorber. So if you see an old truck or tractor inner tube, grab it!

(And if you need even thinner rubber sheet, a bicycle inner tube is a good source.)

Forced Air Cooling of Electronics

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I recently pulled apart a vacuum cleaner and came across an unusual component. On the one of the small electronic circuit boards inside the machine was a black plastic box, complete with two hose nipples. The nipples connected to hoses that disappeared off inside the casing of the vacuum cleaner.

So what was the component? Inside the box was a small heatsink mounted on a power transistor - what the designers had done was to use some of the airflow generated by the vacuum cleaner to actually cool the transistor! Pretty trick, eh?

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The lessons for cars are obvious: electronic things that get hot (like injector dropping resistors, ignition modules and even under-bonnet mounted ECUs) can have specific ducting from the grille to keep them cool. Even a small amount of airflow makes a major difference to temps; keeping these items away from hot parts of the engine and ducting cool air to them is likely to radically reduce their heat build-up.

Eight Sockets in One Tool!

When you browse a tool shop and see something new, it’s always a toss-up as to whether it’s worth buying. The logic goes like this: if such a tool was worthwhile, wouldn’t it have been invented long ago and already be in widespread use?

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Well, the other day I took a punt on a pretty cheap ‘socket wrench’. It’s like a large spanner that integrates eight different sized sockets into the one design, with four sockets at each end. They’re accessible on rotating heads. The sizes are 10, 12, 13, 14, 15, 17, 19 and 21mm – and many people will immediately recognise that these sizes have been picked well... they cover most metric bolts in common use.

And the good news is I’ve found it to be a really useful tool, ideal for when you’re unsure of the nut or bolt size but only want to grab one tool, and also very useful when you’re working on a piece of gear with lots of different bolt sizes. It’s awkward in confined spaces and of course has no ratchet facility, but in real-world use I’ve found it to be a good tool that’s worth buying.

Digital / Analog Intake Air Temp Display

Measuring intake air temperatures is important if you drive a turbo car – high intake temps reduce power and also increase the chance of detonation. If you constantly monitor intake air temps you’ll also learn the pattern of when they’re at their highest – for example, in many turbo cars, highest intake temps actually occur after the car has been idling in city traffic on a hot day. Not so good when the driver then guns the car off the line.... By watching intake air temps you’ll also know when to activate an intercooler water spray.

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Recently, a great little temp gauge has become available at a rock-bottom price. Available on eBay and sold as a digital thermometer for PCs, it incorporates both analog and digital displays (the digital display measuring down to a resolution of 0.1 degrees C!) and comes with a sensor.

It’s designed to work off 5V but because it takes such little current, you can pick up that 5V source off the ECU – eg on the TPS feed. I’ve also run it off 12V but that’s not recommended for long periods. The sensor cable will need to be extended for most automotive use, but that’s no hassle. The measuring range is quoted as being -10 degrees C to 80 degrees C.

But the best thing is the price – at the time of writing, AUD$9.48 including post to your door! Do an eBay search for more details.

Hot Air Intake

Everyone knows that you should aim for the coolest air intake for your engine. Colder air is denser, and denser air has more oxygen in it, allowing the mixing of more fuel and resulting in more power! Colder intake air also allows more ignition timing advance to be run before detonation occurs, again resulting in more power. So why would you ever want a hot air intake?

I recently moved to a small town outside of Canberra and let me tell you, the winter temps are way cooler than Queensland’s Gold Coast where I previously lived. So? Well, one thing I’ve been able to observe is that on these cold days, my car’s fuel economy is clearly worse. That’s probably because while cold air is good for power, it’s not so good at evaporating the fuel atomised by the injectors. As Honda found out with their turbo F1 cars of the 1980s, where best fuel consumption was achieved with an intake air temp of 70 degrees C, warmer air can improve fuel consumption.

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So what I have done is remove the trunking that connects the air box to the cool air external of the engine bay, and replaced it with a bell-mouth mounted directly on the airbox. The air that is breathed has therefore passed through the radiator, and is consequently much warmer than it would otherwise be. The result? Fuel consumption is back to normal.

It’s not something I see staying there all the time – come summer and the original cold air intake will go back on.

Salvaged HID Lights

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I recently came across a discarded late-model headlight (I think it was from a Mini) and grabbed it. What attracted my attention was the high intensity discharge (HID) low beam. Could it be salvaged and made into a working light, I wondered?

But first a warning: HID lights use dangerously high voltages that are potentially lethal, especially if water enters them. Do not ever touch a working HID system and ensure that in use, others also cannot touch any part of it except an on/off switch on the 12V supply side.

If you haven’t recently looked inside a modern headlight – let alone an HID design – such lights can be pretty baffling. The socket on the plastic housing may have as many as eight connections, the optical assembly may have up to three bulbs, and there are likely to be two separate reflectors and potentially also a glass convex lens present in the assembly.

The first step is to mentally split the system into three light sources – high beam, low beam and parking lights. These are likely to all use different bulbs, reflectors and (possibly) lenses. The next step is to see if there’s any beam levelling system present – most HID lights have the capacity to adjust beam angle so as not to blind oncoming drivers when the rear of the car is laden. The ground connection on all the light sources is likely to be shared. Finally, HID is likely to be used for only the low beam – the high beam and parking lights are typically conventional incandescent.

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In the headlight I salvaged, things were considerably simplified by extracting the headlight assembly from the plastic housing, and then removing the high beam bulb, the associated wiring and the low beam levelling motor (there was no parking light). In fact, that left only two power supply wires to the HID control box – brown and yellow. The brown wire was also shared with the (now snipped off) high beam wiring, so that implied it was a ground wire. Connecting positive 12V to the yellow wire and ground to the brown wire brought the light to immediate life.

A brilliant 12V light? You’d better believe it! (But also believe the warning stated above: unless you know what you’re doing, leave it well alone.)

So that’s it for another AutoSpeed Tech Tips – if you liked these, do a site search for more.

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