Thread: Idle dip
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Old 01-30-2015, 11:10 PM   #20
ztan
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Join Date: Jul 2013
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I never had this problem on stock injectors, have had some idle dip and stumble with higher flow injectors whilst tuning.

<I think> my problem has been that there has been insufficient fuel from the port injectors operating in a non-linear range and the engine going lean.

Before I got my injector scaling and minimum PI IPW right, I would get PI IPW times that were under the linear range with latency added - the revs would dip on switchover to PI and then STFT would shoot up a couple of log lines later, sometimes 20-30%.

Now I've got some minor driveability problems at low load - minor hesitation at low throttle. Logs show this most often happens when I go from DI to split DI:PI operation and my PI IPWs again put the injectors under the linear range - there is a switch in fuelling and by STFT jumps by 15-20% after the hesitation. I'm going to try playing with DI:PI ratios to have full DI operation with lower load and kick in PI later when the IPW will be more linear.

Unfortunately, however, I don't think we have full control of DI:PI ratio stuff in the idle situation yet.
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