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Thread: C7 Z06 Hesitation at WOT

  1. #21
    Potential Tuner
    Join Date
    Nov 2021
    Posts
    3
    Also having the same issue. Bone stock. I replaced the fuel rail pressure sensor but still no joy.

  2. #22
    Potential Tuner
    Join Date
    Oct 2021
    Posts
    9
    Hello guys,
    Quick update : I went to my tuner, we put the stock map back on the car with regular gas and went for a quick spin around, tracking the car datalogs. We noticed the same phenomenon on the datalogs (aka a huge enrichment at WOT around 4k rpm and a slight drop of fuel pressure), however, it wasn't noticeable while driving (no hesitation were felt). My tuner looked at the datalogs really closely during a good 45 min (1st run ever on stock map, 1st run on the E85 flexfuel map but still running regular gas, 1st run on E85 flexfuel map but this time with 100% E85, runs with another E85 flexfuel map which was refined, and finally the last data when I came back with stock tune and regular gas) and apparently, the car put a kind of "safety" that cause the huge enrichissement of the mixture. The common point to ALL the datalogs was the exhaust temperature : at exactly 930?C, the ECU asks for the huge enrichment, that causes the fuel pressure to drop drastically for a slight moment, causing the hesitation I felt only when running my E85 flexfuel tune, either on E85 or regular gas. The enrichment value was 0.74 ! So my tuner just "moved" this safety or whatever this is, earlier at 870?C and changed the enrichment to 0.8.

    Now it's running very good on my flexfuel map running regular gas. I also did one pull with 100% E85 and it seems to be working (ps : in winter, or E85 in Paris is actually E65, plus I had like 10 extra liter of regular 98 octane gasoline so I think the mixture was around E40/E45) (I pushed the car at the redline, WOT, in second gear, third, fourth and until 5500 rpm in fifth gear, still at WOT). I will try to do a couple of other pulls when the ground get a bit dryer ^^' But I would really like to find out what is the ethanol content I can run safely (when pushing the car hard) to keep everything working fine. When I go for a long trip there is no prob of running 100% E85 because I don't go pass 2.5/3k rpm nor floor the pedal on the highway, it's just cruising.

    I will link the datalogs before and after the change.
    I will also update when I did more pull with the car.

  3. #23
    Potential Tuner
    Join Date
    Oct 2021
    Posts
    9
    Here are the datalogs :

    BEFORE : enrichment of 0.74 lambda, at 930?C

    avant.png


    AFTER : enrichment of 0.8 lambda, at 870?C

    après.png

  4. #24
    Senior Tuner
    Join Date
    May 2003
    Location
    South FL
    Posts
    1,359
    Sounds like Cat Overtemp was still enabled and the tuner removed it or greatly reduced its ability to richen the fuel mixture.
    [email protected]
    Owner/GM Calibrator
    Gen V Specialist - C7 Corvette, Gen6 Camaro & CTS-V3

  5. #25
    Cat overtemp. There's a drop-down tab to disable. However, I have found on some os's you still get the enrichment even when set to "disabled". I'll always also set the cot enrichment the same as the power enrichment.

  6. #26
    Potential Tuner
    Join Date
    Oct 2021
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    9
    Quote Originally Posted by 32vape View Post
    Cat overtemp. There's a drop-down tab to disable. However, I have found on some os's you still get the enrichment even when set to "disabled". I'll always also set the cot enrichment the same as the power enrichment.
    What do you mean ?the same as the power enrichment? ?

  7. #27
    Potential Tuner
    Join Date
    Oct 2021
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    9
    Quote Originally Posted by 32vape View Post
    Cat overtemp. There's a drop-down tab to disable. However, I have found on some os's you still get the enrichment even when set to "disabled". I'll always also set the cot enrichment the same as the power enrichment.
    Yeah Cat Overtemp apparently but why does GM put that in the stock ECU ? It?s not even overheating at 930?C, is it ?
    Do you think what my tunner did was good ? Because I still get an enrichment as I told you on my previous reply. But it?s running super fine at WOT, I now can?t feel any hesitation even when I run E40 or E50.