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Thread: RPM pulls backward under load.

  1. #1

    Default RPM pulls backward under load.

    LS3 408ci, HP, twin turbo, smart coils, E85. During a pull on the dyno, at 6000 RPM or so, the engine will pull back down and stop the RPM. I thought it was the converter locking up or something wrong with it, so I put another one in. It did the same thing just at a different RPM by like 100 RPM. We added boost to it, it made more power, but did the same thing. Added timing and it move the drop out a little further out, a little better, but still doing it. It's like a cylinder is dropping out under a load, when I drive it on the street and get on it, it'll spin and go to 7200. But as soon as I shift, it pulls down to 6000 or so and stay there. Have you ever seen this? (Sensor bad, push rod length, smart coil?) Any suggestions would be greatly appreciated. Thanks for your time.
    Click image for larger version. 

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    Dyno New tran (zipped) Folder.zip dynonew trns8.zip
    Last edited by lballog; 09-21-2020 at 07:33 AM.

  2. #2

    Default

    That datalog just looks like the converter is working properly. They do the same thing on launch if they're specced right. Flash up, roller over, tighten up pulling the RPM down, then back up in the RPM.

  3. #3
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    1,944

    Default

    What transmission? Are you monitoring transmission fluid temp when this issue occurs?
    Why does the power curve peak, then go right to left then back to left to right? I've never seen a power curve do that. Gary

  4. #4

    Default

    Fixed it. Found that it was the cam sensor. Changed it, now it goes to the rev limiter, 7200 RPM. Thanks everybody.

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