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Thread: Need some help with LS3 tune

  1. #1
    Tuner in Training
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    Need some help with LS3 tune

    I have a friends car to try and improve the driveability. He had a shop build it and then they quit before it was finished. It's a 57 Chevy with a 2010 L99 and 6L80e, supposedly from the same car but the trans OS doesn't match a Camaro. The engine has some sort of Tilden Ultra4 cam in it, long tube headers, 3" dual out with an x-pipe and no cats, and has had the AFM and VVT physically removed. I think the fuel system is a GM pump because I don't see a regulator anywhere, one line straight to the rail....so 58psi. I think it still has the stock Torque converter. I spent a bunch of time on an Eddy current dyno and had the VVE pretty well dialed, but every day it seems to be different. I'm also having a tough time getting the idle to be stable. I turned off all the adaptives I could find and it still varied the timing and the throttle opening. It just oscillates and can't find a stable idle...which I think is making the slow speed driveability...crappy. The engine keeps hunting for an idle and is loading and unloading the cam making it really tough to drive slow. Getting pretty frustrated at this point, so I'm probably missing something.

    Today I went through this guide

    https://forum.hptuners.com/showthrea...e-tuning-guide

    but it would only stabilize every other flash, the other times it would just oscillate or hang at ~1000rpm...even with a 2% change in Airflow final minimum... and I wasn't getting useful data....just making blind timing or final airflow minimum changes, but it seemed to be happier around 10 degrees. I ended up using the parameters from his G8 Best Idle and went for a drive...same issues...and even after 10 iterations of VVE at 1/2 percentage it's all over the place again.

    I'm attaching the last tune from today and the first part of the drive before it went into limp mode.

    Open to any suggestions.
    Attached Files Attached Files

  2. #2
    Senior Tuner
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    There are a lot of things I see that's going. The VVT isn't disabled in the tune. The min airflow tables are really really low. I would expect them to be around 8-9 g/s with that combo, not 4.0. Make sure there are no vacuum leaks that are causing the issue. I'd start with that...

    It would be easier, IMO to do a MAF tune with the E38, but you'd want to make sure that your MAF is in a good location and installed in a properly sized tube.

  3. #3
    Tuner in Training
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    Quote Originally Posted by kevin87turbot View Post
    There are a lot of things I see that's going. The VVT isn't disabled in the tune. The min airflow tables are really really low. I would expect them to be around 8-9 g/s with that combo, not 4.0. Make sure there are no vacuum leaks that are causing the issue. I'd start with that...

    It would be easier, IMO to do a MAF tune with the E38, but you'd want to make sure that your MAF is in a good location and installed in a properly sized tube.
    Thanks, I assume you mean the variable cam section under the airflow tab. I hadn't really touched anything there, but I did zero out the VCP (variable cam spark). Now that I look at a stock 2010 Camaro LS3 I see it has values in a lot of those variable camshaft tables, and also under VCP. So is it just the one drop down (camshafts) that determines ALL the VVT tables the PCM is referencing? Or is there somewhere else it needs to be turned off?

    I am leaning towards a vacuum leak somewhere, just haven't had a chance to spray around the manifold and see what happens...I'll make that a priority.

    I do plan to do the MAF as well but the idle was terrible in MAF only so I decided to do the VVE first and then come back to the MAF once I had some airflow values.

    The min airflow numbers are waaay low, I went through several iterations of logging and lowering and got pretty much no change. At least with the oscillating idle I was unable to get it to stabilize per the idle tuning thread and it seemed to run the same regardless of what was in that table.

  4. #4
    Senior Tuner
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    You can change the cam from 1 to 0. I usually 0 the VVT table as well, but isn't really necessary. You also should change the VVT related DTCs to No Error Reported.

    It sure sounds like a vacuum leak. It would certainly explain the issues that you're having.