Does Rev Limiter, cut sparks or fuel ?
Discussion
In my ponderings about a launch control system I am undecided about how to control the engine. For the time being it is staying with the standard ECU as this years Emerald budget has gone on a Diff rebuild. Presumably the Lucas ECU does it by cutting the fuel, which seems a rather unpleasant thing to do to the engine at high revs and probably full throttle opening. The alternative is to cut the sparks, but this sends un-burnt fuel into the cats which will presumably get rather hot and eventually expire.
The system I am thinking of will literally be used as launch control, once under way it will be disabled, currently I prefer cutting the sparks over the fuel. Probably a better solution would be to control they throttle butterfly then the fuelling could sort itself out but that is a bit more complex.
Any thoughts anybody ?
The system I am thinking of will literally be used as launch control, once under way it will be disabled, currently I prefer cutting the sparks over the fuel. Probably a better solution would be to control they throttle butterfly then the fuelling could sort itself out but that is a bit more complex.
Any thoughts anybody ?
Throttle butterfly control?
Can that be done without drive-by-wire throttle control? The ECU would need to move the butterfly.
Can the Emerald control that? I didn't think it can, and I can't see anything in my Emerald software to enable it.
V8D are putting an Emerald in for me at the moment. I will ask when I go up to see it mapped.
Can that be done without drive-by-wire throttle control? The ECU would need to move the butterfly.
Can the Emerald control that? I didn't think it can, and I can't see anything in my Emerald software to enable it.
V8D are putting an Emerald in for me at the moment. I will ask when I go up to see it mapped.
Thanks for the replies.
Ok I will go the spark route then. I will build the electronics myself and controlling the LT side of the coil should be fairly easy. Cutting individual targeted sparks however would be a little more difficult.
Thinking about it the spark route should give quicker response than controlling the butterfly as my Micro can effectively turn on and off the power without waiting around for the Mr Lucus to think about things.
Ok I will go the spark route then. I will build the electronics myself and controlling the LT side of the coil should be fairly easy. Cutting individual targeted sparks however would be a little more difficult.
Thinking about it the spark route should give quicker response than controlling the butterfly as my Micro can effectively turn on and off the power without waiting around for the Mr Lucus to think about things.
Theres been some recent discussion about this issue in the jap forums, some of the aftermarket rev limiters cut the ignition or one side on the coil, problem is when it reverts the timing of the initial spark is not in sequence for some reason. This causes no end of issues with det & engine damage, so beware of exactly how you go about doing it.
The Lucas system cuts the fuel. This isn't what you want at high revs and full power, but you should only be on the rev limiter for an instant rather than leaning on it.
If you're looking for something for launch control then it doesn't need to have infinite authority, it just needs to stabilise the revs when you have the throttle about right, it doesn't need to hold them steady with your foot to the floor and no load on the engine.
By the way, I built something similar (full throttle gear shift controller with crude rev matching) based on a simple aftermarket shift light and rev limiter. No reason not to DIY if you prefer, but all the building blocks you need are available off the shelf.
If you're looking for something for launch control then it doesn't need to have infinite authority, it just needs to stabilise the revs when you have the throttle about right, it doesn't need to hold them steady with your foot to the floor and no load on the engine.
By the way, I built something similar (full throttle gear shift controller with crude rev matching) based on a simple aftermarket shift light and rev limiter. No reason not to DIY if you prefer, but all the building blocks you need are available off the shelf.
Edited by GreenV8S on Sunday 30th December 22:52
Can’t think why the first re-enabled spark would be in the wrong place, certainly not with a Dizzy system. Perhaps if a modern ECU is using Knock sensing to set the timing it may end up in the wrong place. As Pete says I hope not to be leaning hard on the limiter, more a case of fine control.
If I could gather data quickly enough and control the engine more accurately that my foot does it should be possible to device a servo loop that keeps the wheels just at the point of spinning regardless of the grip level. What I have in mind is something that can optimise the engine output for the first 2-3 seconds then it will be disabled.
No doubt something could be bought off the shelf but part of the fun is designing and building the system. If fact I was shown a bike system recently that does launch and rev limit cut for full throttle gear changes, that system cuts sparks rather than fuel.
If I could gather data quickly enough and control the engine more accurately that my foot does it should be possible to device a servo loop that keeps the wheels just at the point of spinning regardless of the grip level. What I have in mind is something that can optimise the engine output for the first 2-3 seconds then it will be disabled.
No doubt something could be bought off the shelf but part of the fun is designing and building the system. If fact I was shown a bike system recently that does launch and rev limit cut for full throttle gear changes, that system cuts sparks rather than fuel.
steve-V8s said:
If I could gather data quickly enough and control the engine more accurately that my foot does it should be possible to device a servo loop that keeps the wheels just at the point of spinning regardless of the grip level.
In that case your problem is controlling the clutch rather than the throttle. The launch control systems don't solve this, but they make it easier for the driver by taking care of the throttle control so the driver can concentrate more on the clutch - they also reduce the scope for getting it wrong by preventing the revs from flaring.GreenV8S said:
The Lucas system cuts the fuel. This isn't what you want at high revs and full power, but you should only be on the rev limiter for an instant rather than leaning on it.
My mistake, I assumed it was sparks as it was so brutal, and programmable, but of course stopping the injector pulses has just the same effect---ouchMark
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