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Thread: Major issues after taking car in to get tuned

  1. #1
    Tuner in Training
    Join Date
    Aug 2009
    Posts
    27

    Major issues after taking car in to get tuned

    Bottom Line Up Front: I am requesting some help identifying any obvious issues with my tune.

    Not here to bash the shop but after over a month of them having my car, them doing mods that I didn't authorize and the tune not being finished (I didn't even get a dyno sheet) I need to vent a little and ask for advice. I originally took my car (06 GTO with TVS2300, Forged 5.3, LS9 Cam, Ported Heads, Headers, 8 Rib conversion, dual in tank pump system with external FPR, meth inj) to this shop to basically t/s the tune at WOT as i was experiencing a hard nose over at about 5000rpm and horsepower peaked at 5400rpm (475rwhp@21psi). I had checked everything i could think of, mechanically, so I figured it was in the tune (2 BAR OS).

    Before they even start the t/s they say I need a 3BAR map sensor based on my boost levels. Something in my brain said 2.5 BAR but i couldn't remember why and these guys tune a ton of LS cars so i figured they knew what they were talking about and I said okay. It was only after getting the car back home and delving into the tune that i remembered the hard limits of the E40. So, the MAP characteristics are completely wrong for the sensor and i suspect that's part of why the car is driving/starting so poorly.

    They also converted to an LS7 MAF sensor (this wasn't authorized by me) and it would appear they are assuming WAY to much flow at lower frequencies. Not sure if this is tied to the MAP being off or what but I'm sure its contributing to the drivability/starting issues I'm having.

    That's the pertinent stuff. I've attached a copies of the tune both when i dropped it off and and after i got it back. Any help would be greatly appreciated.
    Pre-JBA Base Tune.hptJBA Base Tune.hpt

  2. #2
    Not entirely familiar with GM, however I do notice something wrong with the injector offset table. It would appear from the tune that the car is using a 1:1 Fuel Pressure Regulator, and this was accounted for in the injector flow rate table, however, it was not accounted for in the injector offset table. Assuming the car is running a base fuel pressure of 58psi, then the 0 Vac column values need to be copied across all vacuum columns. This will cause very poor fueling. I can't comment on the rest but that is just something that caught my eye.

  3. #3
    Tuner in Training
    Join Date
    Aug 2009
    Posts
    27
    Thank you. Im actually reading up on injector scaling right now trying to figure this out.