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Thread: Idle surging once car comes to complete stop...

  1. #41
    Advanced Tuner
    Join Date
    May 2009
    Quote Originally Posted by pontisteve View Post
    Are you saying that because you scaled the tune (presumably to get around the injector size limitation in the PCM), that you also had to double your running airflow table?

    I don't see how doubling the integral and proportional rpm error was necessary. Does it idle just fine if you didn't do that part?

    I don't know since I did both at the same time. I think the biggest thing was doubling the airflow tables. In a scaled tune, the airflow tables are only guesses because when you take 5LEs method of finding the airflows on a scaled tune it is incorrect. I doubled and even added some little by little until everything smoothed out.
    2018 Infiniti Q60s

    2004 350z/LS2: ERL 434ci, 11.8:1,TFS245cc,262/266@113+3,Fast102,NX 102 plate,60#injectors/return w/twin 255s
    Old setup: CNC'd317s, Fast 102, 228/228@114, PT88,83#injectors/full return system. 10.84@138

  2. #42
    Potential Tuner
    Join Date
    Aug 2019

    Idle surging once lifting the accelerator pedal abruptly

    Quote Originally Posted by DSteck View Post
    With big cams, I have spark correction maxed out by 100rpm error. A huge cam isn't going to want to idle rock steady like a stock cam, so over and under speed error needs to be rectified quickly. I have tried the dead band approach, and it just makes idle swing even more. Timing will get jumpy as hell with really aggressive over and under speed, but the idle speed won't fluctuate too far from commanded idle speed. I also only use a maximum of about 12-15* for correction instead of 22 like some stock setups use.
    Hey I just wanted to say thanks. I have had a problem with idle surge for far too long. Its a gen3 5.3L mounted up to a Porsche transaxle. I'm thinking the clutch/flywheel is quite a bit lighter than OEM. So every time I played with the overspeed/underspeed timing I changed both tables and the problem persisted. I read your post and thought yeah maybe its slowing the engine down too fast during hard deceleration. So I just took 50% off the timing on the overspeed table above 100 rpm. Left the underspeed table alone. Took it for a drive and did some hard deceleration runs. Each time it came back to idle so smoothly. Just like stock. Again thanks so much.