[Yosh6]

This is a drag strip launch starting in D, off idle smash. Hesitation shows up on the RPM Graph (see blue arrow) as a flat line or dip. This one started at 2833 rpm and dipped to 2701 rpm and then started back up again. Just wondering if this is common. Would like to see a straight line from launch to 1-2 shift. Right? Would appreciate some comments on what this may be and if it is abnormal, what is the fix. Thanks

[cmitchell17]

I see the RPMs decrease on my logs in some areas as well and wonder the same exact thing, how are rpms going down? The only thing I think it could be is the TCC clutch is applying or either a clutch in the trans is. You can see the 8L90 start handing off to the next clutch once you hit your WOT shift mph, but it usually dosent drastically drop off and actually does a good job of slipping both on-coming and off-going clutches to keep rpms steadily increasing until it hits the redline then brings on full-apply of the on-coming clutch with a torque reduction.

[KingLT1]

I remember Brett saying that is common on 2018 cars....however I though he could fix it with tuning, but I see he already tuned it.

[steelheadrob]

I see slight drop or flattening at around 3,300 rpms but nothing quite as noticeable as you are see.

[Yosh6]

Thank you for the comments. This has been up for a day and a half and looked at over 90 times. Nobody has commented that they have the exact same issue. That leads me to believe it is something very unique to my car. This issue has been there for a long time and was in my first logs back in June of last year. I do not suspect anything in the tune. Brett knows what he is doing and has found nothing in the tune that could cause this. If it were any gear other than first, I wouldn't be as concerned. Don't want anything hurting the 60'. Still looking..... Thanks again.

[cmitchell17]

Could you post your log file?

[Yosh6]

I don’t think so, but thank you.

[PRAY]

Looking at the logs you send this is where the converter flashes to and then once it is coupled the rpm rises again. So when you smash the gas off idle holding the brake a little as we have discussed in the past it will hit a flat spot for a bit as the converter hits it's flash point and the car starts to move. Look back over all your logs, it will be there. There is no fix except for an aftermarket converter. This is normal in every car with a stock converter and even the non stock converters. It is not as pronounced in non stock converter cars. Your flat spot is actually shorter than a stock geared car. But your converter seems to flash a little higher right up front since you have the launch technique down. But as the converter couples it drags the motor down a hair, the gears are exacerbating this issue. If you graph out your converter slip over your trans slip you will see the slip rpm coming down at this point.

[Yosh6]

Thanks, Brett. Detailed explanation greatly appreciated. Checking this off my list of things to worry about.