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Chapter 4 A dyno run is an excellent way of finding out what’s happening with the engine management system in a modified car. Among other things, it can indicate if the mixtures are too rich or too lean, or if detonation is occurring which is normally inaudible on the road. Modif ying Car Electronic Systems Modifying your car’s electronic systems is not as difficult as you might think and it needn’t cost the earth. S INCE ALL CARS RUN a lot of electronic control systems, it stands to reason that making mechanical engine modifications is invariably followed by a requirement to make electronic modifications. But what are the different approaches available? This book is primarily devoted to the DIY way but that doesn’t mean we shouldn’t have a good look at other approaches that may be available. Sometimes, doing it yourself with a simple tweak will give great, costeffective results. At other times, it makes more sense to take it to someone else to get the work done. However, if you don’t know what can 26 PERFORMANCE ELECTRONICS FOR CARS and can’t be done, you won’t be able to make the right decisions! Do Nothing? As we’ve seen in earlier chapters, engines run oxygen sensors to tell the ECU when the mixture is too rich or too lean and knock sensors to tell the ECU when the engine is detonating. Both are closed-loop systems – when the engine is lean, the ECU will feed more fuel through the injectors until it is right, while knocking will cause the ECU to retard the ignition timing or drop boost (or both) until the detonation ceases. So in some ways, even if you mechanically take the engine out of its normal parameters, it will mostly adapt to the change (although not necessarily at full load). However, that’s a story which is increasingly changing. With some current cars, if you tweak the boost or fit a new exhaust, you may see no power improvement. That’s because the parameters that the ECU is working to have been tightened to the extent that if anything gets out of the ballpark, the ECU decides that something is going wrong and takes action accordingly. Many current turbo cars, for example, go bulk rich when tweaked to even a minor degree. In these cars, the mechanical mods won’t cause any engine damage but at the same time, siliconchip.com.au A great DIY modification on any turbo car is to fit an intercooler water spray, using a high-quality nozzle like this Spraying Systems design. It can be triggered by a dedicated controller, a voltage switch working from the air-flow meter output, or by an injector duty cycle switch. the results won’t be nearly as good as they might have been if there had also been electronic modifications. Some older cars are quite different. Start extracting more power out of them and they’re fine – there’s enough capability in the standard electronic systems to cope with the changes. Not just cope, in fact, but also take advantage of them. Finally, there’s a third category where modifications can quickly cause real engine danger (or damage) – the system (both electronic and mechanical) is already right on the edge. So where does your car – and your modifications, either actual or proposed – fit into this? We can’t give you a definite answer – it depends so much on the car and what has been done to it. One easy way of getting some valuable information is to do a chassis dyno run, with a good wideband air/fuel ratio meter analysing the results. If the air/fuel ratio at full load is very rich or is lean (the dyno workshop should be able to tell you the actual numbers that indicate either of these conditions for your car), then electronic mods to the management system will increase performance and/ or longevity. So if you’ve made a few mechanical engine mods (eg, an exhaust, cold air intake, a bit of boost or a cam) and everything seems fine, take it along for a dyno run and check the power output and the mixtures. Ask the workshop to also listen carefully for detonation. If they have a factory service reader for your car (eg, the Tech 2 for Holdens), ask them to plug it in and see what things look like. Obviously, you need to pick a reputable workshop where siliconchip.com.au Fully programmable management systems like this MoTeC unit are excellent quality products. However, the increasing capability of factory ECUs means that these units are now best left to race cars or older, heavily modified cars. The Pulsar ET is a great budget package with a heap of DIY possibilities. From the small and poorly-located vane air-flow meter through to the ease with which power can be boosted, it’s an ideal car for making electronic modifications to match the upgraded engine mechanicals. they know what they’re doing and will tell you the truth! New Chip Let’s keep the typical scenario go- ing – you’ve made some mechanical mods aimed at lifting power by around 25-30% and after your dyno run, you find that the power is down a bit over what you’d hoped and that the air/fuel PERFORMANCE ELECTRONICS FOR CARS 27 Want to get away from the mainstream and make some unusual electronic modifications – eg, to the auto transmission control of this Lexus LS400? In this case, you can get some very good results doing it yourself. Because many auto transmissions are now electronically controlled, they can be easy and cheap to modify. ratios and/or ignition timing aren’t quite what you need. One solution is to call a chip seller, tell them what you’ve done and ask them to send you a new one. This revised chip will – hopefully – have software that will better match the new gas flows through your engine. It might drop the fuelling a bit at the top end, advance some mid-range timing and pull back high-load, high RPM advance, for example. All that sounds fine – if in fact it actually suits your engine! However, in reality, it’s quite unlikely that the mods you’ve made exactly match the mods made on the guinea-pig car that was used when the chip was being developed. So if your car’s exhaust flow is a bit better or your cold-air intake is a bit worse (in real life maybe it’s a hot-air intake!), then the chip that you’ve just paid for may not be very suitable. Worse, if you’ve made no mechanical mods at all and it’s not a turbo car where the boost can be turned up by a new chip, where’s the extra power going to be coming from when the chip’s based on another car? It’s much, much better to have revised software produced expressly for your engine – ie, run your car on a dyno and have someone reprogram the software in real time to give the ignition timing and air/fuel ratios that suit your car. This approach is more expensive and often more of a logistics hassle but it does give very good results. 28 PERFORMANCE ELECTRONICS FOR CARS In fact, on some cars, it can give decent power gains, especially if they have been modified. This can also apply to mechanically standard cars – primarily because the software is being optimised for that particular car (even cars straight from the factory have differences, while the factory ECU software is a generic, “one-sizefits-all” program). Interceptors Another way of altering the way in which the ECU works is to fit an interceptor. Although sometimes sold as if they are a complete engine management system, all that an interceptor does is to take the input signal (say from the air-flow meter) and alter it, before sending it on its way to the ECU. As a result, the ECU is fooled into thinking that the engine is behaving differently to how it really is and changes its outputs accordingly. For example, if the ECU thinks that less air is passing into the engine, the mixtures will be leaned – ie, less fuel will be injected. Similarly, if the ignition timing signal from the crank position sensor is altered, then so will the spark advance. Interceptors are not as good as properly revised software – there’s a lot that they cannot do (eg, change the sensitivity of the knock sensor) and occasionally they do more than they’re supposed to. As an example of the latter, if you change the air-flow meter signal, not only will the fuelling change but so (to a degree) will the ignition timing – one of the main determinants of ignition timing is engine load! However, interceptors are very useful in a many situations. The first is when there’s no-one around who can break into the factory software and rewrite it. The second is when you’re on a tight budget. Some of the projects in this book are based on interceptors – because they can be made so cheaply, they are an unbeatable value for money compromise. Interceptors can also be used on all car electronic systems – including engine management, variable weight power steering, auto transmission control, electronic 4-wheel drive systems and climate-control systems. Finally, interceptors can be used while keeping the entire factory system intact. This means that you can easily remove any add-on devices and return the car to standard – electronically at least. Programmable Management A hot-wire air-flow meter like this one has an analog output voltage which is easy to modify. You can change mixtures right through the range, allowing you to fit bigger injectors, for example. A programmable ECU completely takes over the handling of spark and fuel – in older cars, you can literally ditch the factory ECU. On really heavily-modified cars, a programmable ECU is still a top choice – we’re talking greater than (say) 50% increases in power. In those cars, the factory ECU is way out of its depth – even with major changes like new injectors and a new air-flow meter, it will be struggling to cope. However, programmable ECUs do siliconchip.com.au have some downers – and they get worse for more recent cars. In any car of the last decade, knock-sensing will be an important part of the factory management system and programmable ECUs invariably don’t have any knock-sensing facility. Also, on more recent cars, the factory ECU is likely to talk to the auto trans, security system, cruise control, dash – and so on. None of these functions – let alone things like stability control and electronic throttle control – can be carried out by programmable ECUs. The only choice then if you want to use one of these devices is to disable maybe half of the electronic systems in your car or to use the programmable ECU piggyback style. This is where the programmable ECU controls just fuel, ignition and idle speed – and the factory ECU keeps doing all the rest. But even this isn’t ideal – again the links to the body systems (eg, the fuel usage readout of the trip computer) won’t work and you’ll still have lost knock sensing. If real-time re-programming software is available for your car, one of the best ways of making modifications is to have the software re-mapped on the dyno. If available, a factory-supplied diagnostic tool can also be used to monitor the engine management system during the re-mapping process. Here, a Holden Commodore is being modified by ChipTorque, a Queensland-based company that specialises in performance-tuning Budgets And Power A workshop that I have visited many times has a sign: “Speed costs money; how fast do you want to go?” They’re right. But a lot depends on how much you’ve actually spent to get to where you are now. Say you’ve got a $10,000 turbo 4-cylinder car and you’ve done the simple and (relatively) cheap steps – new exhaust, cold-air intake, bigger intercooler and more boost. You’ve spent maybe $3000 doing this and now you want to tweak the management system. Perhaps it’s running out of fuel at high engine loads and you want to fit larger injectors – this will definitely need electronic as well as mechanical mods. Conversely, the engine may be running way too rich at full load. Good programmable management will set you back well over $2000, while an interceptor could be about $1000. Real-time software re-programming on the dyno is another approach, again costing about $1000. By contrast, doing it yourself and changing the air-flow meter signal with a voltage modifier might cost you $75, or maybe $175 when you include a dyno tune of the device. We know what we’d do! Consider also some of the other siliconchip.com.au An older turbo car like this Cordia is a great example where DIY electronic modifications can be brilliantly cost-effective. Unless you’re building something very special, it’s simply not worth putting a new programmable management system into a car like this. modifications you might want to carry out, such as tweaking the auto transmission shifts, changing the power steering weight and so on. They could be done by a $1000 interceptor but by the time the workshop understands what you want changed and does it for the first (and probably only) time, you won’t see much change out of $1500. But you’ll be able to do it yourself with some of the projects in this book for one-tenth of that. It’s an easy choice, isn’t it? But let’s change the scenario. Own a $40,000 car that’s commonly modified and so has lots of well-proven mods available for it? There’s probably not a lot of point in inventing new techniques and in this case, it’s best to do what others do and visit a good workshop. Of course, instrumentation and other such add-ons still make perfect DIY sense – no matter what the cost of the car. So think it through before deciding whether to dive into engine management mods yourself or to take a more traditional path. There are excellent arguments for both approaches and it depends very much on the car, the modifications required and your  budget. PERFORMANCE ELECTRONICS FOR CARS 29