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Thread: Suggestion for future EFI software.

  1. #1

    Default Suggestion for future EFI software.

    I'm still very new at this EFI thing, so shoot me down if you like, but here goes. I would like to see IAC Hold Position by temperature.

    My engine is a hottie, so may not apply as much to more mild combinations. It needs 100% IAC when cold to maintain (or get close to) set idle for at least one minute or so. So with the IAC Hold set at the recommended 20-30% (I prefer zero), every time you blip the throttle the IAC drops to this and of course the engine stumbles when you let off as the IAC ramps back up to maintain fast idle. Situation even worse with my preferred setting of zero. If the IAC Hold was settable by temp, you could note the position of the IAC at multiple temperatures as the engine warmed up & mimic this with the Hold Position graph. That way when you blip the throttle, the IAC would not move much and the engine should go straight back to its previous idle. Probably not that hard to do either. Thoughts?

  2. #2

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    This is an interesting idea. I have never heard of any ECU using this feature either. Have you tried messing with your IAC speed or "RPM Above Idle To Start Ramp" and raising the value?

  3. #3

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    No I haven't. But when the engine is at operating temp, I don't really like any IAC Hold. So I have it set to ramp at the max 2000 above idle, and fairly quickly if I do have some set. While changing these parameters may help when cold, I'm sure I wouldn't like the characteristics when hot. I currently have it set at 20% just to try and alleviate this issue a bit. Not that it's a big issue.

    A bit more info. So when 'cold' I have to reverse up a hill through a garage & up another slope. So even as the engine is warming up a bit, say with the IAC at 80%, it's annoying as when you touch the throttle the IAC drops to 0, 20, 30 whatever it is set to, and as I let off, the RPM of course drops right down until the IAC can get back up to its 80ish percent. If the Hold Position was programmable by temperature, I could easily stop it doing this and still have my preferred option of zero hold at full temp.
    Last edited by 66FAIRLANE; 02-23-2018 at 12:24 AM.

  4. #4

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    Could I see a datalog, I think we can fix this with the given EFI software.

    The IAC Hold percentage (activated when the TPS >0%) is intended the be the highest value you can get without the engine "hanging" the RPM to return back to idle. And once the TPS is 0% the IAC will move & fluctuate to maintain the Target Idle Speed for the given temperature (the IAC Position at idle/0% TPS will always be higher when it's cold vs hot).

  5. #5
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    Are you using the Sniper EFI for timing control? If so, is your Idle Spark enabled?

  6. #6

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    No, I don't use Sniper EFI for ignition control. Sorry no datalogs yet. Haven't even explored that feature yet.

    I have the throttles set so the IAC is just operational in neutral (when hot of course), so that I have the maximum left for cold starts. This means around 20ish% in drive when hot. Have tried both 20% & 30% Hold Positions, but of course this doesn't help when cold. I don't want to have an 80% or so Hold value, which would help when cold because as I've stated before, my preferred setting is zero. It's no big deal, but would be a nice and probably not that difficult to add, seeing as it's there are already many temperature based tables.

  7. #7
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    If your IAC Position is around 20 in gear at idle, I would open the throttle shafts a little to lower the IAC Position. Your out of gear idle RPM may go up a little, but it may help your problem.
    Last edited by 81 TransAm; 02-23-2018 at 09:47 PM.

  8. #8

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    Had considered that just to get some more IAC air when cold. But it won't help much with the actual issue. As I said, its no big deal, would just be nice to have.

  9. #9
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    It should help because it will be relying on the throttle shafts to get air at idle (which doesn't change), not the IAC.

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