TKOGTO

or at least acts like one with ridiculous power lag on throttle application coming out of certain corners.

Was @ the Glen Mon/Tues. In the first couple of laps of a session, the motor responded with power immediately after adding throttle coming out of T7. As the session progressed, a delay creeped in between application and power delivery whch got worse as the run progressed. By Tuesday, it felt like I could count to 3 before the power kicked in. The motor sounded like it was bogging down, not getting full fuel or O2.

The car is a 2018 Grand Sport with the A8.

Any ideas? The same thing happened with my prior 2018 A8 GS [in T7 @ WGI and Oaktree @ VIR].

CPB

The automatic is known to overheat on track, so I'd imagine that it was limping. What were the trans temps? Also below 3K rpm the car pulls some throttle mapping to like 60%.

Oskee

The corvette C7 motors are not turbo charged !

LT1 motor is a naturally asperated motor (no supercharger or turbo)
LT4 motor is supercharged in the Z06
LT5 motor is supercharged in the ZR1

Big difference between a turbo charger and a supercharger !

CPB

He wasn't being literal. He's throwing shade at the car acting like it has turbo lag due to the on track performance he experienced.

Oskee

Then I stand corrected !

TKOGTO

Something is not right but thinking it's not the trans temps. They maxed out @ 208 on Mon and 219 on Tues, well below overheating and they are at least 10*F lower when it starts happening.
RPMs bottom out 4.5k at these points on the track as you want the lowest gear possible for max torque on exit.

CPB

How were water and oil temps? I know the car constantly adjusts timing based on temp conditions, torque demand tables and PTM.

TKOGTO

Not sure what they were at the time it would start to occur. Oil maxed out @ 275 which is fine for the A8. Water max was 219 but these were at the end of the sessions.
Change from Sport 1 to Sport 2 had no effect.
Torque demand is the highest at these 2 spots on the tracks.

BrunoTheMellow

sounds like you were spinning the tires.

TKOGTO

Are you thinking the car is heavily loaded on the left rear [turning right and going steeply uphill] and the right rear with so much less weight on it is spinning faster? The active handling senses this and pulls timing/cuts power?
The left rear can't be spinning, it is carrying the bulk of the weight as you pass the apex.

64drvr

Engine oil temps are not directly correlated to trans fluid temps. Quite possible your trans was very hot as the A8 really sucks for track work. What PTM mode were you using?

TKOGTO

Something is not right but thinking it's not the trans temps. They maxed out @ 208 on Mon and 219 on Tues, well below overheating and they are at least 10*F lower when it starts happening.
Started in Sport 1, thought that might be the issue so went to Sport 2 - no difference at all.

6DoF

what style limited slip do these cars have? (gear vs clutch)

if it's clutch, it's possible your clutches went away slowly making the issue get worse. 100% guess just adding possibility to your guess/statement ...

BrunoTheMellow

Yes and yes. Was the car making a different exhaust gargling sound?

TKOGTO

Yes, like it was about to bog down with a meduim hum thrown in to make it sound like a blown speaker while listening to "...And Justice for All"

BrunoTheMellow

exactly like 1:00 in this video (45 seconds into the lap) ? If so. Yes. That’s traction control kicking in

64drvr

PTM Sport 1 is pretty conservative in yaw and wheelspin tolerance. PTM Sport 2 is a good bit more lenient. Have you tried PTM Race?

TKOGTO

Thanks. I will check my PDR video and data.
Appreciate the assistance.

TKOGTO

I didn't. First day out with new to me car after total loss @ VIR last Oct.
It is interesting to me how correlated the lag is to temperature. It takes a good long while in the first session for it to occur then comes on more quickly, progressively getting worse as the day goes on. By the 4th session it kicks in on lap 1 or 2. It can't be speed related as I am not consistent enough to be going quicker every successive lap.

ShadyVette

I’ve run the Glen twice in my 19 GS A8 and have not had that problem. I’m more of a novice so take my observation with a grain of salt.

what was your gear into T7 and what was your alignment and tires? With cup2s (runflat) the track was a dream. But after a weekend they were done so I’ll be going back to PSS. The PSS (runflat) get squirrely when hot, I usually start a session at 27 / 28 PSI. What we’re your tire pressures at the end of a session? Cup2 and PSS can get to 36 on a hot day when starting from 28 PSI. Anything past36 isn’t great in this car.

I sometimes take T7 in second gear hit 3rd before the dirt and 4th before the crest of the hill. I’m in sport 2. And I’ve had street alignment so far. This year I’m moving to track alignment specs. Traction control would be quite obvious as I’ve had it kick in at Thompson when in sport 1 and it’s quite disruptive.

EDIT: When I say I grab 2nd gear it’s mid turn before the apex. (you can’t grab second on turn in as the speed is too high and generally the computer won’t give it to you until you scrub speed in the turn) As I mentioned above, the transmission is so smooth you can do that as the speed scrubs off just before you apply throttle before the apex.