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Message: <blockquote data-quote="xbalance2002" data-source="post: 1236114" data-attributes="member: 24760">About different types of management system upgrades and airflow meters versus MAP sensors. stressed the importance of good tuning. "The skills of the tuner are vitally important, whatever the approach you take," he says. It's all too easy to plough your money into hardware, neglect tuning and end up with a car that is temperamental to start, thirsty, down on power and high in emissions. In this article we'll explore engine management tuning.Dyno TuningIt doesn't matter if you've opted for an interceptor, piggy-back, stand-alone system or a factory ECU remap, there is one step that cannot be avoided - the engine must be tuned on a dynamometer. The majority of workshops have only the facility to tune the car on a chassis dyno, but the bulk of extensive tuning is ideally performed in an engine dyno cell. Most people steer away from engine dynos since the engine must be removed from the vehicle, adapters may need to be fabricated and there are greater costs involved. "The time it takes to tune an aftermarket stand-alone computer depends how much base programming comes with the computer, the characteristics of the engine and your experience with the given injectors etc," says David Alexander. "A MicroTech system comes with a program that should run the engine, but some of the sophisticated ones with more parameters arrive pretty well blank - for example, an Autronic, MoTeC or a new Wolf 3D." This can have a considerable effect on the time and cost involved in tuning. In most situations, you probably spend four hours tuning a stand-alone system on the chassis dyno."Some engines may take longer if they have unusual characteristics at certain sites. "Engines with hand-made intake manifolds, relocated injectors and big cams make it difficult to achieve a good result that spans the whole way through the rev range. "On top of that, some ECUs take a lot of keystrokes and so take longer to tune than others. Some also lack the parameters you need to achieve a good end result, so you end up wasting time trying to fix it some other way." The base mapping of fuel and ignition comes largely through experience - knowing where an engine might need ignition advance, or where it might be safest running rich comes from prior experimentation. Most tuners enter the initial batch of timing values very conservatively and first focus on the amount of fuel flowing into the engine. Ignition timing values are usually set second, specific to a particular fuel octane and (where appropriate) boost level."During a typical tune the inlet air temperatures vary hugely, so you end up with tuning across a reasonable temperature range," says David. "Most systems have air temperature correction, but there's more to it that that -there's the location of the temperature sensor and all kinds of variables. I think intuition is more important in tuning for different temperature ranges. In the case of an interceptor, you don't have to go back and worry about all of these parameters. All you usually want to do is get in there to make a couple of tweaks to the existing system - like lean the mixtures at certain sites - and that's it. Everything else is already correct. The same goes for a remap of an original ECU," says David. "And that saves a lot of time."Mapping on the RoadOnce the engine has been extensively tuned on a chassis dyno, is it necessary to then hit the road to tune for real-world drivability?"It's certainly necessary to road test the vehicle once it's been chassis dyno tuned. I can get it running pretty right on the chassis dyno because I've been on there for such a long time but, regardless, you still need to put it on the road."There are some times when you need to do some mapping on the road at very light throttle, trailing throttle and over-run situations - things you can't quite simulate on the dyno."Decel is often included as part of an emissions test and you can't really pull the kind of manifold vacuum on the dyno that you can on the road. You can also get the right acceleration characteristics from those heavy vacuum conditions and it's also easier to determine if the decel shut-off resume might not be at the right point."So, yes, there are certainly times when you need to take the car out onto the road and give the tune a tweak in those light load areas."How Car Manufacturers Tune Their EnginesDon't expect that a perfect tune can be achieved with only a very short time on a chassis dyno. To put things into context, we need to consider the efforts that car manufacturers put into mapping production engines. Literally thousands of hours are spent making changes, numerous engines are put through torturous durability testing and followed by extensive on-road testing. This typically involves testing in weather extremes (snow field to the desert). These are the lengths that must be taken to ensure a car performs in all conditions. Cold StartHaving done stories on countless cars with programmable management, AutoSpeed has noticed that a very high number struggle in cold-start conditions. We asked David Alexander about the problem."Well, the proper definition of cold start is a window that's only open for a number of seconds. Once you get any heat into the combustion chamber, the cold start environment is pretty much gone. "You can get cold start characteristics right through experience, but there are some engines and set-ups that are a real challenge - factors like fuel temperature, fuel pressure, ambient temperature, combustion chamber design and ignition timing all play a part."Whenever I tune a system I always get the car until the next morning when I can go in and set the cold start and warm-up cycle parameters."For sure, though, factory computers have a lot more starting maps than any other aftermarket computer. The new Wolf system has quite a few starting strategies these days, but even a factory system from fifteen years ago has something like a hundred. The limitations of programmable systems is certainly a major issue in that particular area of tuning".Factory Mapping v Aftermarket MappingThe car companies set their cars up to cope with every conceivable condition that might be experienced in any part of the world. They'll also draw upon their experiences in every part of the world and they'll enter the according data into the ECU - it may never be accessed in the lifetime of the vehicle, but it's always there."With an aftermarket system you can get very good results for what is typically a narrower application. You can get the car so it's nice to drive on a day to day basis, but to get things spot-on for every condition you'd have to spend weeks playing. And in many instances you'll never be finished because of limitations in the flexibility of the aftermarket computer. The brainpower is relatively limited. "Winter and summer changes in local fuel mixes can cause detonation issues if you're tuning for absolutely ten-tenths. On the other hand, the knock-sensed factory systems - particularly the new Subarus - with closed-loop fuelling and timing will keep the engine running as well as it possibly can. They're really extremely advanced."</blockquote>

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