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      05-15-2016, 09:16 AM   #1
dc_wright
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DTC Issue at Daytona

Ran a PDX on the full IMSA course at Daytona Friday 5/6. Lots of fun out on the high banks, but I had an interesting issue with DTC on. First session on every about pass around the 30 degree banking about 2/3 of the way through the turn I could feel DTC activating intermittently on on the rear brakes alternating between left and right sides. Felt a bit like tramlining feels but in the rear of the car. 2nd session it was kicking in less frequently and then on about the 8th lap every ABS/DTC/DSC warning light came on. Brakes were still fully functional and after pitting and cycling the ignition off and on they all cleared and everything looked like it was functioning normally. Didn't get to go back out that session due to a full course black flag from an "incident" in turn 1 that was blocking the track.
For session 3 I turned all the nannies off and ran with no issues. A couple of friends indicated they've heard of similar issues with spec E46 and 330i cars having the same issue at Daytona, and they unplug the yaw sensor and just ignore the warning lamps.
Just curious if anyone here has experienced the same?
And in answer to the question of why didn't I just turn everything off at the start, I just put new tires on the rear and I didn't want to run without ABS and risk flat spotting a brand new RE71 if I over braked and locked up a wheel momentarily.

Here's the video if anyone's interested. Due to the session 2 incident they asked us to leave extra spacing, don't dive bomb anyone to force your way by, and to watch your mirrors and let obviously faster cars by without making them close up on you. If there was no one in your mirrors when you passed turn 6 and headed out onto the banks, and there was a car coming up on you at the bus stop, they were obviously faster and you should let them by in the next passing zone. Same thing going through the tri-oval and coming up on turn one. Some people got the message, some people didn't. I did quicker laps in session 2 and had a bit more open track without anyone holding me up, but it was still a blast to run.

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      05-15-2016, 12:58 PM   #2
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Long, LONG time ago I went for a ride with a friend who has an E46 with StopTECHs at Auto Club Speedway, and with DSC active we can feel the outside front brake activating in short intervals despite zero slip with a periodic and rhythmic "thump."

The census is the banked oval confuses the crap out of traction control systems because even when the car is not slipping, there's a huge differential between the wheel spin on both sides while the yaw sensor is telling the car's ECU that it's going straighter than the wheel spin differential indicates.

Especially with DTC mode, the sensors are screaming "spin" while the yaw sensors are reading a completely contradictory set of data, that the "direction" of travel is still relatively straight compared to the steering angle but the acceleration data says the car is turning away from the center of the turn. On a banked oval DTC would try desperately to get the two set of sensor data to mesh, and desperately brake the outside wheel to "prevent" what it perceives as lack of traction, while DSC is disabled the information about the slip angle and banking isn't being calculated and considered.
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      05-15-2016, 01:46 PM   #3
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Quote:
Originally Posted by The HACK View Post
Long, LONG time ago I went for a ride with a friend who has an E46 with StopTECHs at Auto Club Speedway, and with DSC active we can feel the outside front brake activating in short intervals despite zero slip with a periodic and rhythmic "thump."

The census is the banked oval confuses the crap out of traction control systems because even when the car is not slipping, there's a huge differential between the wheel spin on both sides while the yaw sensor is telling the car's ECU that it's going straighter than the wheel spin differential indicates.

Especially with DTC mode, the sensors are screaming "spin" while the yaw sensors are reading a completely contradictory set of data, that the "direction" of travel is still relatively straight compared to the steering angle but the acceleration data says the car is turning away from the center of the turn. On a banked oval DTC would try desperately to get the two set of sensor data to mesh, and desperately brake the outside wheel to "prevent" what it perceives as lack of traction, while DSC is disabled the information about the slip angle and banking isn't being calculated and considered.
This was my take on it too. Just looking to see if anyone else had experienced it in a Z4. Seems like it's a common experience with steeper banking. Thanks for the input!
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      05-15-2016, 01:51 PM   #4
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Interesting information. Thanks for sharing!
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