Throttle drop between shifts

[BigMike42]

Hello, I have been chasing this issue for a while. Car is a 2016 C7 A8 H/C/I. This car wasn't fully tuned by me and I am new to Gen 5 stuff, so I have been spending a lot of time trying to figure out the torque modeling. I had an issue where 4th gear would just simply not lockup no matter what after a shift. I was able to resolve that by making sure 100% torque management is on for the shift. It had been .7 prior.

The result now is that TPS is dropping between shifts. I decided to go back to the stock torque model and simply just up my driver demand in the top 3 rows. This got it *sometimes* only using spark to control the shifts, so I figured I must be on the right track. I simply put the torque model back to stock, upped the driver demand, and upped the peak torque values.

The problem is it still intermittently drops throttle between shifts and I cannot figure out what I should look at. I attached two logs and the tune. One log, I had four 2-3 shifts in a row not drop throttle. The other log, however, you can see the throttle drop right at the end of the shift.

log-2to3-nothrottledrop.hpl
log-2to3-drop-throttle.hpl
c7-torque-testing.hpt

[GHuggins]

Well, in all fairness you actually have one of the sucky 8sp cals to tune. Problem is all of the "actual" shift time controllers are missing from the calibration. SO, I'll try to explain what to do to "help it" make the shift.

First for what it's worth I'll explain the basic "logic" of how the controller "looks" at the shift. To put it simply - torque management and everything doesn't "per say" matter - if it doesn't "think" it can make the shift in it's designated time frame then it will cut throttle or whatever to make it happen.

Now using this the basic work arounds especially since the shift timing controller tables are missing are as follows. AND fore warning - the higher you make the shift rpm and speed the harder it's going to be... With that said you have shift rpm at 7100, but the mph settings should be commanding something around 6200ish rpms. These need to be closer together - try to make the mph 3ish mph less than the rpm target. Make sure the 100 row in the regular shift speed setting is the same as the wot shift speed setting.

Now, you're going to be better off to disable TM cause the next 2 are trying to force the shift - also don't understand why this killed the tcc because it shouldn't have - add 1 to the 525 and 600 NM inertia settings then start increasing shift pressure (main limit - your actuals are already pretty high). I personally absolutely despise having to increase shift pressure to make a shift - really really prefer to have the shift timing tables and prefill tables to make it work right, but.... Then you "might" also need to increase the last 2 columns of the airmass and map tables by 100 at their top rows then smooth. This all combined with your DD mods should make it work. AGAIN, hate doing it this way, but when you don't have the tables you just have to work with what you have.

[BigMike42]

Well, in all fairness you actually have one of the sucky 8sp cals to tune. Problem is all of the "actual" shift time controllers are missing from the calibration. SO, I'll try to explain what to do to "help it" make the shift.

First for what it's worth I'll explain the basic "logic" of how the controller "looks" at the shift. To put it simply - torque management and everything doesn't "per say" matter - if it doesn't "think" it can make the shift in it's designated time frame then it will cut throttle or whatever to make it happen.

Now using this the basic work arounds especially since the shift timing controller tables are missing are as follows. AND fore warning - the higher you make the shift rpm and speed the harder it's going to be... With that said you have shift rpm at 7100, but the mph settings should be commanding something around 6200ish rpms. These need to be closer together - try to make the mph 3ish mph less than the rpm target. Make sure the 100 row in the regular shift speed setting is the same as the wot shift speed setting.

Now, you're going to be better off to disable TM cause the next 2 are trying to force the shift - also don't understand why this killed the tcc because it shouldn't have - add 1 to the 525 and 600 NM inertia settings then start increasing shift pressure (main limit - your actuals are already pretty high). I personally absolutely despise having to increase shift pressure to make a shift - really really prefer to have the shift timing tables and prefill tables to make it work right, but.... Then you "might" also need to increase the last 2 columns of the airmass and map tables by 100 at their top rows then smooth. This all combined with your DD mods should make it work. AGAIN, hate doing it this way, but when you don't have the tables you just have to work with what you have.

Thank you for the detailed response. I am going to the track today so maybe I'll get a chance to mess with it. It's a 4k stall, so when it unlocks in 4th it loses 3 mph and like 2 tenths, very frustrating.

I was told these 8 speeds are finicky in the C7 with the TCC lockup. However, I am certain once I put 100% TM back in on the 3-4, it stayed locked the entire time. It is almost like it is sensing abuse and unlocking the converter right after the shift in that particular gear.