Hi all,
I'm a little stuck on how to proceed so I'm after advice.
My car was mapped a while ago now but idle was never fully finished. It has always been quite good at idling hot and not so good when cold. When cold it will oscillate until over 40 degrees to which it then smooths out and becomes generally good. However I've been trying to dial it in better but it appears when its running at temperature advance is -5 degrees(ATDC) which is the lower limit and when cold its at 35 degrees(btdc) which is the upper limit. Also when coming up to a roundabout the rpm drops down to like 6-700 rpm and then slowly raises back to 900(idle target). It sounds like it needs the throttle opening more to allow more air in but that would then make the hot idle situation worse. Hot idle lambda is around 0.91/92 at cold idle it was closer to 0.8 I've been thinking theres an air leak making hot idle ignition retard to much but then it would make the cold idle better
4 Cylinder petrol engine with lightened flywheel and crank pulley 8:1 comp
thanks
idle using advance
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Re: idle using advance
I've had situations with stepper/iac idle control where they do that if the trigger rpm to start controlling idle is too high (different ECU), and it starts trying to control when decelerating to intersections - So, because you are decelerating the rpm is being held up artificially and so the control strategy pulls duty(timing in your case) so when you push the clutch in at the intersection the engine dies.
Check what the timing is doing in the overrun areas of the table, as I sorted and engine which was doing the opposite and hanging up high due to high timing in high vaccum holding it up for a long time before idle control pulled in; could have the opposite issue and bumping up the timing in those areas might help it stop dipping.
Check what the timing is doing in the overrun areas of the table, as I sorted and engine which was doing the opposite and hanging up high due to high timing in high vaccum holding it up for a long time before idle control pulled in; could have the opposite issue and bumping up the timing in those areas might help it stop dipping.
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Re: idle using advance
The fuel map on my engine is set up to have a fuel uplift at 700 rpm on zero throttle opening with normal idle like yours at 900rpm. This means that as the engine speed drops below 900rpm fuelling is increased to prevent the engine stalling when the throttle is suddenly lifted off.