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Help with timing drops post shifts, 1st and 2nd.

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  • Help with timing drops post shifts, 1st and 2nd.

    I am recently seeing timing drops only after shifting from 1st gear and 2nd gear. The car only has JB4 and running an additive map 6. +7.8psi on e20. I've been running this map since Jan with no issues. I would usually hit 4.5-4.6s from 0-60 and 12.8-12.9s in the 1/4mile. My logs on these runs looks good and don't see any timing drops. But lately, the car has slowed down a bit from 0-60. It can't go below 4.8s and 13.0 in the 1/4. At first I thought it was due to traction as my tires are getting a bit worn out, but the car is awd and I don't hear any tires slipping during 1st and 2nd. The timing drops post 1st and 2nd gear are now consistent, no matter what I do. Traction control off/on or DSC off/on. I see them on Map 0 as well. I ran the car on Map0 for a couple of weeks to see if somehow things will get back to normal, still no luck. Spark plugs checked out good, gaps are 0.022. I started to notice this after me experimenting with brake boosting instead of activating launch control. I was told this yields faster acceleration times on these cars, which is actually not true. I did this a few times but ever since then, I started to see some drops. But now they are consistent. The car still pulls strong, except shifting to 2nd and 3rd feels like I'm shifting manually, just quick hesitations. I also do not see any major issues on 3rd gear pulls other than my trims are high on map6, but on stock map they are fine. I don't think this is a tuning or map issue. Maybe tuning can fix it. Maybe the Transmission Control Module needs to be reset? I really don't know. Any suggestion helps. The log P58_M6_230129_0103 was done before I started seeing this issue just for comparison.
    Attached Files

  • #2
    It seems like the car is boosting higher than normal during shifts compared to the previous logs I’ve done before without this issue. I’m thinking of adjusting ASBR higher than 60. If this can possibly fix this, what number should I start with? 70?
    Last edited by jhl422; 04-15-2023, 01:25 PM.


    • #3
      I think I might have fixed it by adjusting the ASBR. Started with increasing it to 70, 80, 90 and 100. In the first log (230415_1709) the first two pulls, the ASBR was set to 70. In the last pull, it was set to 80. In the second log (230415_1848) the first two pulls, the ASBR was set to 80. In the third one, it was set to 90. In the last one, it was set to 100. There are still some timing drops but in the runs with 80+ ASBR, the timing did not hit 0. Also, throttle seemed to have remained opened between shifts. Before, throttle would dip down significantly in between shifts. I’m going to do a 1/4 mile run tomorrow and log it.
      Attached Files


      • #4
        TBH...its really going to be just like you're doing, finding what works best for your scenario as I don't have a tried and true method to share with you.

        These cars have some adaption that takes place, then of course fuel, traction, environmental, etc. all play a part. You can add duty bias tuning to the mix as well as that will also affect throttle closures. The JB4 works great off the shelf but when you start getting really picky about the fine tuning, it definitely takes some time and patience to dial everything in for peak performance.

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