[paradoxical3]

I track my car often and am having a very frustrating problem. After going after it hard (advanced group 30min sessions) the car noticeably loses power. I figured it was an overheating issue but the oil temp rarely goes above 255 since it is a N55. I finally scanned the car for codes with the BMWhat app and found the following:

Fault: :unknown failure / Speed Sensor rear Right / Driving power reduction by DSC command / Brake disc temperature is too high for a short time
Code: 5F1C

I have stoptechs in the front, but the rears are just stoptech powerslot rotors. How can I prevent this stupid car from cutting my power when I drive hard?

This occurs even with DTC and DSC are FULLY OFF (I never track with them on).

[justpete]

Originally Posted by paradoxical3

I track my car often and am having a very frustrating problem. After going after it hard (advanced group 30min sessions) the car noticeably loses power. I figured it was an overheating issue but the oil temp rarely goes above 255 since it is a N55. I finally scanned the car for codes with the BMWhat app and found the following:

Fault: :unknown failure / Speed Sensor rear Right / Driving power reduction by DSC command / Brake disc temperature is too high for a short time
Code: 5F1C

I have stoptechs in the front, but the rears are just stoptech powerslot rotors. How can I prevent this stupid car from cutting my power when I drive hard?

This occurs even with DTC and DSC are FULLY OFF (I never track with them on).

It's the e-diff which is never off. Only way out is to move to a mechanical LSD. Never had this exact problem but did easily burn up the rear brakes on the track which stopped once the LSD was installed.

[ashmostro]

My sentiments exactly. LSD.

[Cloud9blue]

Does the car actually have a temp sensor in the hub or something? Strange issue indeed.

But you should really consider getting a LSD, especially running at the pace of most advance groups

[paradoxical3]

Interesting, that kind of makes sense. I was originally thinking it was logical for the rear sensor to give the error because the fronts are cooler since the fronts have a full BBK, but I found a document from BMW saying that the rotor temp isn't real, but rather calculated based on brake application force and ground speed. If the temperature is calculated then technically the car doesn't know the fronts are running cooler.

I was running at NCM and my differential was seriously pissed...noticed the need for a real LSD far more than at other tracks I have been to due to the nature of the turns. The car is xdrive, but 80% rear biased. So it makes sense that the car would think that the rear rotors are higher temp if it is over-using the rear pads, and I have noticed accelerated rear pad wear.

[ashmostro]

Originally Posted by Cloud9blue

Does the car actually have a temp sensor in the hub or something? Strange issue indeed.

But you should really consider getting a LSD, especially running at the pace of most advance groups

No i think the DME estimates it indirectly since it knows how much rear brake is being applied to control differential wheelspin.

[ashmostro]

Originally Posted by paradoxical3

Interesting, that kind of makes sense. I was originally thinking it was logical for the rear sensor to give the error because the fronts are cooler since the fronts have a full BBK, but I found a document from BMW saying that the rotor temp isn't real, but rather calculated based on brake application force and ground speed. If the temperature is calculated then technically the car doesn't know the fronts are running cooler.

I was running at NCM and my differential was seriously pissed...noticed the need for a real LSD far more than at other tracks I have been to due to the nature of the turns. The car is xdrive, but 80% rear biased. So it makes sense that the car would think that the rear rotors are higher temp if it is over-using the rear pads, and I have noticed accelerated rear pad wear.

Yep. Has more to do with the fact that this wear is happening under power than intended deceleration. That's why the rears are wearing out faster than the fronts which I agree should get more abuse under decel.

[raceyBMW]

Hmm, if its just through the brake sensor then you could just take it out and tie it up out of the way, but if its through the speed sensor that wouldn't be possible.

[ashmostro]

It's not through the brake pad sensor - those are more of an on-off switch. There is some soft failure but not enough to measure and then remeasure brake temp.

[_Ryan_]

Track car? code it off.

[vtbandit]

Originally Posted by _Ryan_

Track car? code it off.

I'm very interested in knowing more. Do you know what in particular needs to be coded "off"?

[_Ryan_]

Originally Posted by vtbandit

I'm very interested in knowing more. Do you know what in particular needs to be coded "off"?

I suggest speaking with those prepping your track car, I'm sure you can appreciate I'm hesitant to provide instructions to mess with the DTC modules etc.

[paradoxical3]

Originally Posted by _Ryan_

I suggest speaking with those prepping your track car, I'm sure you can appreciate I'm hesitant to provide instructions to mess with the DTC modules etc.

I really need to know how to disable this. I have googled and can't find anything. I am at Watkins Glen right now and it is ruining my weekend, even with a mechanical LSD installed. Can you PM me if not comfortable sharing publicly?

[_Ryan_]

Originally Posted by paradoxical3

I really need to know how to disable this. I have googled and can't find anything. I am at Watkins Glen right now and it is ruining my weekend, even with a mechanical LSD installed. Can you PM me if not comfortable sharing publicly?

Google "NCS Dummy".

[paradoxical3]

Does it have something to do with either E84_AX_REF_DIFF_LOCK or just DIFF_LOCK?

[paradoxical3]

What most people don't realize is that this is killing your car's performance on track. IT won't throw a SES light or any codes, but if you actually scan the DSC module you will see that it is cutting your power due to braking temps. Even if you have a LSD! The next step forwards for the 335i platform is figuring out how to code this off.

If a wheel threatens to slip, it is individually braked: blocking momentum is directed to the wheel opposite, which thereby guarantees optimum drive power. When DSC or Dynamic Traction Control (DTC) is active, the engine power output is also adjusted.
If the sporting driver chooses to deactivate DSC or DTC, he still has the benefit of ADB-X, which then focuses on maximum forward drive and applies braking force only. A temperature control sensor ensures that the brakes do not overheat.

[chris82]

Without an LSD I don't know how this would be resolved, but I believe there is something to code to tell the car you have a mechanical LSD installed. It's a simple on or off? Not sure

[paradoxical3]

I have a mechanical LSD, just am not sure what to code

[paradoxical3]

I just wanted to report back that unlike the extremely unhelpful user _Ryan_, Alex@Alpine was incredible.

Alex was able to code out the e-diff and "brake disc too high" and my car now behaves properly on the track.

[ashmostro]

Does that code out work under all traction control modes or just when it is fully turned off?

Thanks

[paradoxical3]

Originally Posted by ashmostro

Does that code out work under all traction control modes or just when it is fully turned off?

Thanks

Not sure as I don't remember the last time I drove with DSC or DTC on, but from what I understand about how it works I believe it should work all the time.

[ashmostro]

Interesting... I think I need to try this out. I'm definitely cutting power on the track, despite my suspension and LSD mods...