128i Throttle Limp Issue on Track

[jox5]

Hey all,

I'm driving a new-to-me 128i and just had it out at VIR for my second track stint in it. I had an issue where the car would give me a lethargic throttle, then throttle would disappear, then would re-appear after about 30sec, or if I turned the car off and on right away. Here's some data and I'm hoping someone can help figure out what's going on:

Track: VIR
Temps: 50-65 degrees
Car set up:
Redshift coilovers + camber, factory diff, 17x9 245/40r17 RT660, Ferrodo DS2500 pads, RBF600 fluid, Kassel tune (219whp/214wtq on a Mustang Dyno). My car is also a SULEV N51 car.

I did a skidpad event with the car a few days before my track event and the car did fine with no issues.

I also did another HPDE at VIR back in February. The outside temps ranged in the 40-45 degree range. Had no issues with the car.

On track, after about lap 5 or 6, the throttle goes limp. No lights show up on the dash. It seems to be related somehow to the brakes, diff, and/or ABS. There were a few corners where I either had to trailbrake pretty deep (most likely causing the rear diff to brake the inside wheel) and/or heel/toe. Then the throttle issue would show up.

I'd literally go into pitlane, continue at about 30mph, stop and restart the car, then go back out again.

I'm also driving with DSC fully off. I left it in DTC mode for a few laps but it still did it. I don't have engine oil temp/coolant temp readouts but I did run a whole session blasting my heater on full blast. Throttle limp still happened.

A local guy who tracks his 135 said there were multiple layers of limp mode associated with the DSC system, even when fully off.

Any thoughts?

[markslc1]

https://www.e90post.com/forums/showthread.php?t=1216639

[jox5]

Wow, I think you hit it on the nail. Thank you so much.