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Old 01-22-2021, 08:27 PM   #15
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Quote:
Originally Posted by lt4camaro View Post
My concern , not worry , is a upshift by the auto trans, or hitting the rev limiter which I believe is at 6600 RPM . Not a good scenario for a max effort 1/4 mile pass. Trapping at gear ratio, tire diameter calculated 6200 RPM is not going to be actual RPM with a auto trans due to slippage I think.
There's only one way to find out.

Try it
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Old 01-23-2021, 01:31 AM   #16
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TC slip can be logged via HPTUNERS. Here is some data from my 2019 ZL1 A10.

Pic 1, At idle, TC slip = idle rpm, 100% slip. (self explanatory).

Pic 2, 6500rpm in 6th gear = 1 rpm slip at that point. I rarely see more than 5-9rpm indicated slip once the converter is commanded to lock.
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Old 01-23-2021, 04:05 AM   #17
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Quote:
Originally Posted by RHD ZL1 View Post
TC slip can be logged via HPTUNERS. Here is some data from my 2019 ZL1 A10.

Pic 1, At idle, TC slip = idle rpm, 100% slip. (self explanatory).

Pic 2, 6500rpm in 6th gear = 1 rpm slip at that point. I rarely see more than 5-9rpm indicated slip once the converter is commanded to lock.
Very good.

I’m curious the comparative data used to extrapolate that.
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Old 01-23-2021, 09:08 AM   #18
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Originally Posted by grampa_ss View Post
If WOT, let the trans do the shifting.
Totally agree only if the WOT shift RPM is where I want it to be.
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Old 01-23-2021, 09:16 AM   #19
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Quote:
Originally Posted by RHD ZL1 View Post
TC slip can be logged via HPTUNERS. Here is some data from my 2019 ZL1 A10.

Pic 1, At idle, TC slip = idle rpm, 100% slip. (self explanatory).

Pic 2, 6500rpm in 6th gear = 1 rpm slip at that point. I rarely see more than 5-9rpm indicated slip once the converter is commanded to lock.
Great info and electronic diagnostic proof on what actually happens regarding converter slippage thank you. Does the lock up command happen any time at WOT or after a certain RPM while at WOT in any gear?
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Old 01-25-2021, 04:22 AM   #20
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Originally Posted by lt4camaro View Post
Great info and electronic diagnostic proof on what actually happens regarding converter slippage thank you. Does the lock up command happen any time at WOT or after a certain RPM while at WOT in any gear?
Converter lock / release is based on, Throttle Position vs Road speed. This is independent for each gear.
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Old 01-25-2021, 08:16 AM   #21
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Originally Posted by RHD ZL1 View Post
Converter lock / release is based on, Throttle Position vs Road speed. This is independent for each gear.
Thank you, all good to know.
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Old 03-07-2021, 09:54 PM   #22
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Originally Posted by lt4camaro View Post
Thank you, all good to know.
The TCM commands it to lock up by vehicle speed, at WOT the TCM actually commands the torque converter to lock at 19mph in first gear (on the 8L90). Of course it doesn't actually do that, and with stock TC's it usually doesn't lock at WOT until the very top of second gear so about about 50 mph. My guess is we are missing a lot of the parameters we need to properly control lockup, you can't make it lockup any earlier no matter what you set the speeds too.
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Old 03-08-2021, 07:54 AM   #23
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Originally Posted by cmitchell17 View Post
The TCM commands it to lock up by vehicle speed, at WOT the TCM actually commands the torque converter to lock at 19mph in first gear (on the 8L90). Of course it doesn't actually do that, and with stock TC's it usually doesn't lock at WOT until the very top of second gear so about about 50 mph. My guess is we are missing a lot of the parameters we need to properly control lockup, you can't make it lockup any earlier no matter what you set the speeds too.
My only concern regarding torque converter lock up was how much if any slippage while at WOT at the end of the 1/4 mile to calculate RPM increase. I am using tire diameter, rear gear ratio, and 5th gear ratio (10 speed auto) and estimated MPH trap speed to see what RPM I will be turning . Turns out I would be very close to a upshift and that is not a desireable place to be. The calculation does not differentiate between a auto or manual trans. A manual trans has no slippage, but a torque converter must have some imo therefore rpm should be higher, 200 rpm is critical cause my calculations are that close
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Old 03-08-2021, 09:15 AM   #24
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Originally Posted by lt4camaro View Post
My only concern regarding torque converter lock up was how much if any slippage while at WOT at the end of the 1/4 mile to calculate RPM increase. I am using tire diameter, rear gear ratio, and 5th gear ratio (10 speed auto) and estimated MPH trap speed to see what RPM I will be turning . Turns out I would be very close to a upshift and that is not a desireable place to be. The calculation does not differentiate between a auto or manual trans. A manual trans has no slippage, but a torque converter must have some imo therefore rpm should be higher, 200 rpm is critical cause my calculations are that close
Not if the converter is locked...if it's unlocked then Yes.
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Old 03-08-2021, 02:43 PM   #25
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Not if the converter is locked...if it's unlocked then Yes.
Thank You.....And I have learned since my post was listed, at WOT anywhere close to 6500 rpm red line in that high of the gear count that the converter is locked. Gears 1 and 2 maybe not. What I may do during my tune is raise the fuel shut off from 6600 rpm to 6700 rpm and manually hold 5th gear till I cross the finish line to make sure no up shift or hit the fuel shut off
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Old 03-08-2021, 11:02 PM   #26
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I checked my logs on my A8... And anywhere WOT past about 4400RPM "TCC slip" is +/- 2RPM, before that roughly 50RPM.

One thing I did notice though is the parameter "Trans Slip" which DOES show a significant amount of slip 1500 +/- 200RPM ish for a surprisingly long time right before each shift.

Does anyone have insight on the "Trans Slip" parameter? Im guessing related to TQ management?
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