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Thread: Rpm rises 100rpm after closed loop.

  1. #1
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    Rpm rises 100rpm after closed loop.

    Have a swapped ls2 440 cube 12:1 compression motor running pump gas. Everything is ok, still need some dyno time to dial in timing at W.O.T but the start up and idle as you know takes time. Open loop the idle is where it should be but once in closed loop after about 30 seconds like clockwork the rpm will increase 100 rpms. Doesn't matter if the engine is cold or already warmed up it's only after entering closed loop will it increase. I can change the idle speeds in the charts and it will always go up exactly 100 rpm. I've seen a few posts commenting about this but no answers. Here is my tune along with as comprehensive log and setup as I can offer. Any help would greatly be appreciated. Larry
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  2. #2
    Senior Tuner Ben Charles's Avatar
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    Didn’t look at log... but I bet vac leak an fuel trims add fuel and therefore RPm rise

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  3. #3
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    That's a pretty consistent vacuum leak then. When the desired rpm increases the rpm follows to exact demand so I'm not sure how you think that's a leak but thanks for commenting.

  4. #4
    Senior Tuner Ben Charles's Avatar
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    If it follows commanded then not your problem...

    Didn’t look so saying what I’ve seen from closed loop control and possibly vac leak

    Email Tunes, [email protected]
    96 TA Blown/Stroked, 4L80E/Fab 9
    15 C7 A8 H/C 2.3 Blower/PI
    14 Gen 5 Viper
    Custom Mid Engine chassis, AKA GalBen C