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Thread: LT4, T56 manual transmission - Engine doesn't decelerate between shifts

  1. #1
    Tuner in Training
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    Feb 2015
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    LT4, T56 manual transmission - Engine doesn't decelerate between shifts

    I have a Chevy Performance LT4 crate engine with a T56 manual transmission (Camaro 1967) and - according to GM instruction sheet - is suppose that the ECU briefly cut fuel when you depress the clutch. I wired (as indicated) a top of clutch switch. The issue is that the RPMs doesn't slow enougth between shifts and is impossible to shift normally. Is there any parameter that I could tune to change the time that the ECU disable fuel when it receives the "top of the clutch switch" signal? Or even better, could I disable this preventive control, I mean that ECU doesn't interfiere and it lets the engine revs down normally between changes or when acelerate and decelerate?

  2. #2
    Senior Tuner Higgs Boson's Avatar
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    I disable Clutch Fuel Cutoff on my tunes, maybe you should look at airflow instead, like is the throttle closing properly when you release the pedal.

  3. #3
    Tuner in Training
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    Feb 2015
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    Thanks for your quick answer. The car will be at the painting shop for a couple of days. I will check de Clutch Fuel Cutoff parameter and take a look the airflow too, and then come back with the results. Just to know, did you experience this behavior in LT4+T56 combos? This is the second job where we're using the L4 engine+T56 and both are experiencing the same problem.