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How to Electronically Modify Your Car, Part 1

Part 1 of our major new series

by Julian Edgar

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At a glance...

  • Why electronically modify a car?
  • What skills and knowledge do you need?
  • What equipment do you need?
  • How to learn a completely new field of expertise...
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This article was first published in 2008.

I have been modifying cars for about 20 years, doing it first as an enthusiast and then latterly as a journalist writing about those modifications.

I have rebuilt a BMW engine; turbocharged and intercooled a naturally aspirated engine - including making my own turbo exhaust manifold; I’ve upgraded intercoolers and turbos and exhausts and radiators. I’ve done full suspension makeovers, aerodynamic modifications and rebuilt an auto trans. In the distant past I even internally modified an auto trans valve body to change shift behaviour, developing the whole modification myself. I’ve got a home workshop with a lathe, mill, bandsaw and lots of other equipment.

But I have to say: DIY electronic modification of cars beats mechanical mods hands-down for cheapness, ease of modification and results.

With electronics you can change turbo boost curves to get more performance at the bottom of the rev range – and the top as well. You can improve fuel economy and alter the way the car feels to steer. On cars with active torque split four wheel drive, you can in ten minutes and for under $100 make a greater improvement to handling than spending thousands of dollars on new suspension bits and tyres.

Nothing – simply nothing – beats DIY electronic mods. In fact, if I feel an inadequacy in a car I am driving, I now think: “What can I change electronically?” rather than first considering getting out the spanners.

Examples? Sure.

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My Honda Insight hybrid is one of the most fuel-efficient cars in the world. But for a cost of under $5 I have made electronic mods that measurably improve fuel economy.

When I owned a twin turbo, all-wheel drive Nissan Skyline GT-R, I built a torque-split controller that allowed the front/rear active torque split to be altered by a driver-operated knob. You could change the handling balance literally from corner to corner. In the rain, the handling was simply that of a different car.

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When I owned a Lexus LS400, I found the steering light and lacking in feel. But by using a single adjustable electronic component, I was able to dial-up an increase in the weight of the electronically-controlled steering that gave the driver far better control on the road. By using a second technique that made use of an electronics kit, I was able to make the steering lighter in carparks and heavier on the road, in fact getting increasingly firm as speed increased!

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A long time ago I owned a 660cc Turbo Daihatsu. It featured a big turbo, water/air intercooler and larger injectors. It got to 100 km/h in about 6.9 seconds. Making the standard ECU work with the big injectors cost less than $5 – and the car had perfect driveability.

None of these modifications involved years of study at breaking into the software of car computers; none of these mods was expensive. Most just involved simple measurement of car systems, some thinking, and then testing different modifications.

And all the modifications were extremely effective.

Not the Answer to Everything

DIY electronic modification is not the answer to everything. You can’t change the boost curve of a turbo that isn’t there, or use electronics to improve the flow of a restrictive exhaust. But, in cars that increasingly use electronics to control nearly every system – and in the future of hybrid and electric vehicles, to power the car as well – having electronic modification skills in your armoury dramatically increases the likelihood of doing great DIY car modifications.

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Simple electronics of the sort that is being described is not a closed book. It does not require years of study, formal training or intrinsic brilliance. You do not need an understanding of the whole field of electronics to be effective at making car electronic modifications – you can simply make modifications based on the understandings you have. (After all, that’s just like mechanical mods – how many modifiers would have the ability to design a camshaft from scratch?)

Even an understanding that you can develop in half an hour will allow you to do mods that would otherwise cost hundreds of dollars more if done mechanically – and that’s if they’re even possible to do mechanically...

The Series

In this series we will start from the beginning: you don’t need to have any electronics knowledge at all.

We will introduce concepts that can be built on one another, resulting in a frame of reference that remains the foundation for everything that follows. But that doesn’t mean you need to wade through thousands of words of theory before you can start making modifications. In fact, in each following part in this series we will cover a concept and then immediately apply it to a real world car modification.

You might not want to do that particular modification, but look at the example closely so that you can see how the modification works.

Don’t fool yourself – if you don’t understand it, don’t pretend to yourself that you do! Learning requires honesty as well as an open mind: there are heaps and heaps of tossers who skim something, get a vague gist of what it was all about, and then think they know it.

They don’t.

One really good way of self-assessing whether or not you have learnt something is to say to yourself: can I now explain this idea to someone else? As a teacher and journalist, I know this approach very well – if I can’t explain a newly-learned concept to someone, then I don’t understand the concept.

Electronics is the sort of subject where it is the sequence of ideas that is important. In this series, none of the individual ideas will be at all hard; it is the understanding how those ideas stack together that is vital.


If you do mechanical mods, you need spanners and sockets and a hammer and screwdrivers. If you do electronic mods, you also need tools.

You can try doing electronic mods without any special tools, but it’s just making things hard for yourself. Like using a pair of pliers to undo a bolt, rather than a socket and a breaker bar. You round-off the bolt and then decide you don’t really want to mechanically modify your car any more...

Your need three major pieces of equipment:

  • Multimeter

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The key piece of equipment is a multimeter. A multimeter is a test tool which can measure a variety of different electrical factors - at minimum: volts, ohms and amps. In addition to these measurements, it helps if the meter can also display:

  • duty cycle

  • pulse width

  • rpm

  • temperature

  • continuity

Another very useful function of a multimeter is a 'peak hold' button. As the name suggests, the meter will retain on its display the max value measured. Especially when working by yourself on the road, this allows testing without having to constantly glance down at the meter.

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The best place to buy a multimeter is from an electronics store. While automotive parts suppliers stock multimeters, they can be up to double the price for meters with just the same quality and features. Note that pretty much any digital multimeter will have sufficient accuracy for car use - buy on the criteria of price, features and warranty. Because of the huge decrease in prices over the years, it's not worth buying a multimeter secondhand - many times they are above new price!

  • Soldering Iron

Next on the list is a soldering iron. A general purpose mains-powered iron (eg a 25 or 40 watt design) will perform most soldering tasks on a car - and also can be used to assemble electronic kits and work with individual components.

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However, if you can stretch for the extra dollars, a temp-controlled iron is a better proposition. Not only do they - as the name suggests - allow you to dial up an appropriate temp for the job, but they usually are configured with a base station and a remote iron that's linked to it with a supple cord. The lighter iron makes it a lot easier to use, you get an inbuilt stand and a tip-cleaning sponge is usually also provided.

And don't forget to use solder designed only for electronics use.

  • Power Supply

A variable supply is, I think, an absolute must-have. It’s especially useful if you're building something and want to test it before it gets into the car.

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A variable power supply can output variable voltages and in some cases, variably limit the current flow as well. At realistic prices you're more likely to find power supplies that can supply currents up to 3 amps and have an output voltage range of 0-20 volts.

Most important is to have a power supply that has built-in digital meters to show the current being drawn and the voltage being supplied. Having this information instantly available (sure, you can measure it with your multimeter - but then that ties up the meter) is extremely useful.

Also look also for fine and coarse supply voltage adjustments (so much easier to accurately set the voltage) and the variable current output facility. The power supply should also be completely protected against overload, high temperature and short circuits.


Electronically modifying cars opens up a whole world of incredibly cheap, very easy and highly effective possibilities. Don’t miss out!

Next: understanding circuits

The parts in this series:

Part 1 - background and tools

Part 2 - understanding electrical circuits.

Part 3 - volts, amps and ohms

Part 4 - using a multimeter

Part 5 - modifying car systems with resistors and pots

Part 6 - shifting input signals using pots

Part 7 - using relays

Part 8 - using pre-built electronic modules

Part 9 - building electronic kits

Part 10 - understanding analog and digital signals

Part 11 - measuring analog and digital signals

Part 12 - intercepting analog and digital signals

Part 13 - the best approaches to modifying car electronics and the series conclusion

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