Car cuts throttle when hard braknig

[Phloozy]

So I can now reproduce my heel toe issue and found it stems from throttle being cut under hard braking. While its great I can reproduce it I have no idea how to fix it. Here is a video of what is going on. Basically I can heel toe fine but under very hard braking the throttle stops functioning. If I roll down the street in neutral you can see that with 1 foot on the gas and the other on the brake, the car does not rev at all.

https://youtube.com/shorts/HCQx3jiU-14?feature=share

This has been terrible on track as I cannot heel toe when driving at the limit. This has caused pretty dangerous clutch kicks and inconsistent downshifts. If anyone can help figure this out it would be amazing

[amg6975]

#thankstoyota

I wonder what's the trigger. Is the DSC seeing the throttle position CAN messages and sending a torque cut request to the DME or is the DME seeing brake pressure CAN messages from the DSC and doing the torque cut internally.

I would bet a beer the DSC module is actually the culprit here. If so, maybe the DME could be tuned to ignore torque cut requests, I'm not totally sure. May also be able to run a different DSC from an M3, or tell the DSC the car is a 135 or something?

A man-in-the-middle CAN solution could fix this either way... either by telling the DME there's no brake pressure, or by removing the torque reduction request. That's not the cleanest way to do things though.

Does the 135 have the same issue? It may be BMW being overly cautious of Valvetronic. Can you run the car with the throttle body removed? Maybe it's assuming valvetronic failed and it's closing the throttle body as a safety catch?

[Phloozy]

Originally Posted by amg6975

#thankstoyota

I wonder what's the trigger. Is the DSC seeing the throttle position CAN messages and sending a torque cut request to the DME or is the DME seeing brake pressure CAN messages from the DSC and doing the torque cut internally.

I would bet a beer the DSC module is actually the culprit here. If so, maybe the DME could be tuned to ignore torque cut requests, I'm not totally sure. May also be able to run a different DSC from an M3, or tell the DSC the car is a 135 or something?

A man-in-the-middle CAN solution could fix this either way... either by telling the DME there's no brake pressure, or by removing the torque reduction request. That's not the cleanest way to do things though.

Does the 135 have the same issue? It may be BMW being overly cautious of Valvetronic. Can you run the car with the throttle body removed? Maybe it's assuming valvetronic failed and it's closing the throttle body as a safety catch?

I found some information about cutting a wire that sends brake signal to the ecu could fix this but I tried this last week and had no luck. I think its more related to wheel speed or abs since i can rev with the car not moving and the brakes to the floor. Its only when the car is moving that I am cut out. Sadly I cannot swap ABS modules without taking a points hit with NASA so that is slightly out of the question for me. I am really hoping a standalone isn't the only answer.

[spidertri]

Based on the other threads we've had on this topic and the FB group, I don't recall anyone with a 135 reporting the same issue.

We've also reached out to several different tuners and it seems that none of them could find anything in the DME that controls this or a parameter that they could actually manipulate.

I've started to wonder the same as amg6975, is the DSC module what is actually causing this?

Phloozy are you allowed to reflash your existing DSC module to a different software? There was a guy on here who converted his 135i DSC module to a 1M module and it worked. Check out this thread: https://www.1addicts.com/forums/show....php?t=1712789

Alternatively, we know there are different brake pressure models that can be coded in the DSC module, is it possible that coding the brake pressure model to something from a car with bigger brakes affects this? Does a 128i with sport brakes coded (+spbr) experience this? I should probably try that one myself.

[Phloozy]

Originally Posted by spidertri

Based on the other threads we've had on this topic and the FB group, I don't recall anyone with a 135 reporting the same issue.

We've also reached out to several different tuners and it seems that none of them could find anything in the DME that controls this or a parameter that they could actually manipulate.

I've started to wonder the same as amg6975, is the DSC module what is actually causing this?

Phloozy are you allowed to reflash your existing DSC module to a different software? There was a guy on here who converted his 135i DSC module to a 1M module and it worked. Check out this thread: https://www.1addicts.com/forums/show....php?t=1712789

Alternatively, we know there are different brake pressure models that can be coded in the DSC module, is it possible that coding the brake pressure model to something from a car with bigger brakes affects this? Does a 128i with sport brakes coded (+spbr) experience this? I should probably try that one myself.

I cant program the DSC but I may be able to flash a different oem software onto it.

[amg6975]

Originally Posted by spidertri

Based on the other threads we've had on this topic and the FB group, I don't recall anyone with a 135 reporting the same issue.

We've also reached out to several different tuners and it seems that none of them could find anything in the DME that controls this or a parameter that they could actually manipulate.

I've started to wonder the same as amg6975, is the DSC module what is actually causing this?

Phloozy are you allowed to reflash your existing DSC module to a different software? There was a guy on here who converted his 135i DSC module to a 1M module and it worked. Check out this thread: https://www.1addicts.com/forums/show....php?t=1712789

Alternatively, we know there are different brake pressure models that can be coded in the DSC module, is it possible that coding the brake pressure model to something from a car with bigger brakes affects this? Does a 128i with sport brakes coded (+spbr) experience this? I should probably try that one myself.

I would bet that the DSC module is sending a torque reduction request to the DME, same as if the DSC was going off, or the eLSD was kicking in, etc.

You should be able to flash the DSC unit, I don't really know for sure but I would be surprised if there was a hardware difference between a 128 and 135, and if the DSC theory is correct and the 135 doesn't have this issue, it should resolve your problem.

I also don't know exactly what would happen if you just unplug the DSC or pull its fuse and give it try, but I would bet it doesn't have the issue. But that could be due to several things, like the DME not knowing the wheel speed or brake pressure.

You may even want to try seeing if there are different firmware versions available for your VIN... try the latest version, or the oldest to see if there's an off chance they added or removed this "feature" at some point.

[Phloozy]

Originally Posted by amg6975

I would bet that the DSC module is sending a torque reduction request to the DME, same as if the DSC was going off, or the eLSD was kicking in, etc.

You should be able to flash the DSC unit, I don't really know for sure but I would be surprised if there was a hardware difference between a 128 and 135, and if the DSC theory is correct and the 135 doesn't have this issue, it should resolve your problem.

I also don't know exactly what would happen if you just unplug the DSC or pull its fuse and give it try, but I would bet it doesn't have the issue. But that could be due to several things, like the DME not knowing the wheel speed or brake pressure.

You may even want to try seeing if there are different firmware versions available for your VIN... try the latest version, or the oldest to see if there's an off chance they added or removed this "feature" at some point.

I was told by a tuner that I am on an old firmware but updating it would remove my tune so that could be something to look at. Would I still have abs if I pulled the DSC fuse? I need to look into how to flash the DSC so I can test.

[Phloozy]

Originally Posted by amg6975

I would bet that the DSC module is sending a torque reduction request to the DME, same as if the DSC was going off, or the eLSD was kicking in, etc.

You should be able to flash the DSC unit, I don't really know for sure but I would be surprised if there was a hardware difference between a 128 and 135, and if the DSC theory is correct and the 135 doesn't have this issue, it should resolve your problem.

I also don't know exactly what would happen if you just unplug the DSC or pull its fuse and give it try, but I would bet it doesn't have the issue. But that could be due to several things, like the DME not knowing the wheel speed or brake pressure.

You may even want to try seeing if there are different firmware versions available for your VIN... try the latest version, or the oldest to see if there's an off chance they added or removed this "feature" at some point.

are you suggesting just flash the 135 software onto my existing DSC or to buy a 135 module?

[spidertri]

Originally Posted by amg6975

I would bet that the DSC module is sending a torque reduction request to the DME, same as if the DSC was going off, or the eLSD was kicking in, etc.

You should be able to flash the DSC unit, I don't really know for sure but I would be surprised if there was a hardware difference between a 128 and 135, and if the DSC theory is correct and the 135 doesn't have this issue, it should resolve your problem.

I also don't know exactly what would happen if you just unplug the DSC or pull its fuse and give it try, but I would bet it doesn't have the issue. But that could be due to several things, like the DME not knowing the wheel speed or brake pressure.

You may even want to try seeing if there are different firmware versions available for your VIN... try the latest version, or the oldest to see if there's an off chance they added or removed this "feature" at some point.

I've been trying to read up on it and just see if I can figure out the differences in the wert values between the 128, 135, and 1M and also what some of the DSC parameters are actually changing when you change the value, like DELTA_PSI_BETA_LIMIT.

Last time I checked, a couple years ago, my DSC was at .C0F but it might be worth looking again to see if there's an updated version.

Going back through the guide to electronic nannies thread, YarkoDrives tested a lot of different things trying to eliminate some of the DSC behaviors in SCCA Street class. He disconnected the DSC module from the PT-CAN and it sounds like a non-ideal state (https://www.1addicts.com/forums/show...1216642&page=5 has a lot of his information)

He does mention there being a downshift rev match program, where the car uses the front wheel speed sensors and cuts throttle (post #101). But he own(ed) both a 135 and 128, so I'm not sure if he's referencing a 135 DCT with that statement. Makes me wonder what the car would do if you disconnected the front wheel speed sensors.

Originally Posted by Phloozy

I was told by a tuner that I am on an old firmware but updating it would remove my tune so that could be something to look at. Would I still have abs if I pulled the DSC fuse? I need to look into how to flash the DSC so I can test.

This would be updating the software on your DSC module, the engine tune is on the DME and shouldn't be changed with just updating the DSC. But as far as I can tell, I have one of the later DSC modules and I still have this issue.

Originally Posted by Phloozy

are you suggesting just flash the 135 software onto my existing DSC or to buy a 135 module?

Flash the 135 software onto your module.

[Phloozy]

Originally Posted by spidertri

I've been trying to read up on it and just see if I can figure out the differences in the wert values between the 128, 135, and 1M and also what some of the DSC parameters are actually changing when you change the value, like DELTA_PSI_BETA_LIMIT.

Last time I checked, a couple years ago, my DSC was at .C0F but it might be worth looking again to see if there's an updated version.

Going back through the guide to electronic nannies thread, YarkoDrives tested a lot of different things trying to eliminate some of the DSC behaviors in SCCA Street class. He disconnected the DSC module from the PT-CAN and it sounds like a non-ideal state (https://www.1addicts.com/forums/show...1216642&page=5 has a lot of his information)

He does mention there being a downshift rev match program, where the car uses the front wheel speed sensors and cuts throttle (post #101). But he own(ed) both a 135 and 128, so I'm not sure if he's referencing a 135 DCT with that statement. Makes me wonder what the car would do if you disconnected the front wheel speed sensors.




This would be updating the software on your DSC module, the engine tune is on the DME and shouldn't be changed with just updating the DSC. But as far as I can tell, I have one of the later DSC modules and I still have this issue.



Flash the 135 software onto your module.

You flash it first! I'm scared

[xrockoutx]

Originally Posted by spidertri

He does mention there being a downshift rev match program, where the car uses the front wheel speed sensors and cuts throttle (post #101). But he own(ed) both a 135 and 128, so I'm not sure if he's referencing a 135 DCT with that statement. Makes me wonder what the car would do if you disconnected the front wheel speed sensors.

Unrelated/related...I have a 2011 135i with a Wisefab angle kit up front and for a while my front wheel speed sensors weren't communicating (they didn't fit quite right in the new knuckle), this resulted in the car running fine...but SUPER ANNOYING rev hang every time I clutched in (rev match downshifts were non-existent). Eventually I got the sensors to seat back in...and revhang gone.

[amg6975]

Originally Posted by spidertri

I've been trying to read up on it and just see if I can figure out the differences in the wert values between the 128, 135, and 1M and also what some of the DSC parameters are actually changing when you change the value, like DELTA_PSI_BETA_LIMIT.

Unless I'm mistaken the 1M (and M3) have a different hardware unit than the non-M cars. It's actually a far more basic version since it doesn't do a lot of the eLSD and focuses more on performance.

Originally Posted by spidertri

This would be updating the software on your DSC module, the engine tune is on the DME and shouldn't be changed with just updating the DSC. But as far as I can tell, I have one of the later DSC modules and I still have this issue.



Flash the 135 software onto your module.

^ Yeah that, we're just talking about flashing the DSC.

Originally Posted by Phloozy

Would I still have abs if I pulled the DSC fuse? I need to look into how to flash the DSC so I can test.

No, but I'm mostly just curious about testing to see if the issue goes away when it's unplugged. There will be lots of other issues that don't make this a permanent solution.

[Phloozy]

Originally Posted by amg6975

Unless I'm mistaken the 1M (and M3) have a different hardware unit than the non-M cars. It's actually a far more basic version since it doesn't do a lot of the eLSD and focuses more on performance.



^ Yeah that, we're just talking about flashing the DSC.



No, but I'm mostly just curious about testing to see if the issue goes away when it's unplugged. There will be lots of other issues that don't make this a permanent solution.

So mildly inconclusive but I'm pretty sure the issue still remained with the DSC fuse pulled. Obviously had no abs so panic brake testing is a bit more sketchy but when the wheels locked up the revs didn't move until the car came to a stop and they shot up. I say inconclusive because I'm doing no abs stops from 30mph so things happen fast lol It could just be the throttle delay but I am pretty certain it was not.

[Phloozy]

Originally Posted by spidertri

I've been trying to read up on it and just see if I can figure out the differences in the wert values between the 128, 135, and 1M and also what some of the DSC parameters are actually changing when you change the value, like DELTA_PSI_BETA_LIMIT.

Last time I checked, a couple years ago, my DSC was at .C0F but it might be worth looking again to see if there's an updated version.

Going back through the guide to electronic nannies thread, YarkoDrives tested a lot of different things trying to eliminate some of the DSC behaviors in SCCA Street class. He disconnected the DSC module from the PT-CAN and it sounds like a non-ideal state (https://www.1addicts.com/forums/show...1216642&page=5 has a lot of his information)

He does mention there being a downshift rev match program, where the car uses the front wheel speed sensors and cuts throttle (post #101). But he own(ed) both a 135 and 128, so I'm not sure if he's referencing a 135 DCT with that statement. Makes me wonder what the car would do if you disconnected the front wheel speed sensors.




This would be updating the software on your DSC module, the engine tune is on the DME and shouldn't be changed with just updating the DSC. But as far as I can tell, I have one of the later DSC modules and I still have this issue.



Flash the 135 software onto your module.

Attempting to update my firmwares but unsure where to get the most recent sp-daten files. Bimmergeeks have v60 but it looks like they are up to v70 now. Any idea where to get it or if it matters?

[Phloozy]

In the meantime I was able to log PPS and TPS. You can see when hard on the brakes the TPS is shut even though I’m full throttle . It doesn’t come back until I come to a stop

[amg6975]

Originally Posted by Phloozy

So mildly inconclusive but I'm pretty sure the issue still remained with the DSC fuse pulled. Obviously had no abs so panic brake testing is a bit more sketchy but when the wheels locked up the revs didn't move until the car came to a stop and they shot up. I say inconclusive because I'm doing no abs stops from 30mph so things happen fast lol It could just be the throttle delay but I am pretty certain it was not.

That is not what I would have expected. Can you try the same thing but unplug the accelerometer that's under the driver's seat?

Also, with the DSC fuse pulled, does any brake overlap cause the throttle to not function? I don't know how the DME would even know the car is moving.

[Phloozy]

Originally Posted by amg6975

That is not what I would have expected. Can you try the same thing but unplug the accelerometer that's under the driver's seat?

With DSC Fuse still in place? I was going to do that earlier but others with he same issue say they race without that module ever plugged in. Happy to try though. I also have a tuner that thinks they may be able to tune it out. Here is what they said.

"On MSV80, I think I had found some tables specifically related to brake pressure vs. torque limitation. So modifying these should allow for maximum engine torque even while 100% on the brakes and not ruin other safety measures"

[amg6975]

Originally Posted by Phloozy

With DSC Fuse still in place? I was going to do that earlier but others with he same issue say they race without that module ever plugged in. Happy to try though. I also have a tuner that thinks they may be able to tune it out. Here is what they said.

"On MSV80, I think I had found some tables specifically related to brake pressure vs. torque limitation. So modifying these should allow for maximum engine torque even while 100% on the brakes and not ruin other safety measures"

I guess try it with and without the DSC on?

That'd be great if they can tune it out in the DME. I still don't know how the DME could know brake pressure with the DSC module off though.

[Phloozy]

Originally Posted by amg6975

I guess try it with and without the DSC on?

That'd be great if they can tune it out in the DME. I still don't know how the DME could know brake pressure with the DSC module off though.

I will say trying it without abs was harder because i didn't want to go full lock plowing down the street. Its very possible that the car just stopped within a short enough time for the throttle delay to make me think it wasn't working. I would want to do it again with the TPS data logging again to know for sure.

[spidertri]

Originally Posted by amg6975

Unless I'm mistaken the 1M (and M3) have a different hardware unit than the non-M cars. It's actually a far more basic version since it doesn't do a lot of the eLSD and focuses more on performance.

Yeah, that's the conclusion I've been coming to with the different things I've read. It's interesting that the guy in that thread was able to convert his to a 1M DSC.

I did find a comparison spreadsheet that bNks334 put together several years ago. A lot of the 128/135 values have multiple wert_XX choices, while the 1M seems to only have wert_00/01.

When I look at my stock DSC trace file, I don't usually see wert_00 corresponding to the E82 1M chassis in the chassis+motor+options that they list under each. That's not a definitive answer but I wonder what the 1M trace file looks like when you open it in NCS Dummy.

Originally Posted by Phloozy

Attempting to update my firmwares but unsure where to get the most recent sp-daten files. Bimmergeeks have v60 but it looks like they are up to v70 now. Any idea where to get it or if it matters?

When I updated my DME 3 years ago I got V66 from a thread on E90post but it looks like that guy took down his file hosting.

Originally Posted by Phloozy

With DSC Fuse still in place? I was going to do that earlier but others with he same issue say they race without that module ever plugged in. Happy to try though. I also have a tuner that thinks they may be able to tune it out. Here is what they said.

"On MSV80, I think I had found some tables specifically related to brake pressure vs. torque limitation. So modifying these should allow for maximum engine torque even while 100% on the brakes and not ruin other safety measures"

That's incredible news about the tuner and brake/torque tables, please keep us posted if that works out.

Originally Posted by amg6975

I guess try it with and without the DSC on?

That'd be great if they can tune it out in the DME. I still don't know how the DME could know brake pressure with the DSC module off though.

Do you think it could default to fully limiting the torque if it doesn't have DSC brake pressure data?

[amg6975]

Originally Posted by spidertri

Yeah, that's the conclusion I've been coming to with the different things I've read. It's interesting that the guy in that thread was able to convert his to a 1M DSC.

I did find a comparison spreadsheet that bNks334 put together several years ago. A lot of the 128/135 values have multiple wert_XX choices, while the 1M seems to only have wert_00/01.

When I look at my stock DSC trace file, I don't usually see wert_00 corresponding to the E82 1M chassis in the chassis+motor+options that they list under each. That's not a definitive answer but I wonder what the 1M trace file looks like when you open it in NCS Dummy.

Coding the values to the 1M values and disabling some of the additional stuff may have the net effect of mimicking the 1M DSC module but it's not "converting it." I would be shocked if the non-M unit could run the same firmware and such but I have seen weirder things. From what I know the 1M/M3 unit is quite a lot different.

Do you think it could default to fully limiting the torque if it doesn't have DSC brake pressure data?

This is exactly what I'm thinking. I haven't looked at the 128 wiring diagrams much but I have no idea how it would know brake pressure and wheel speed without the DSC putting them on the CAN bus. Only thing I can think is it gets brake on/off switch from the FRM and/or JBBF and says "I can't see the DSC but the brakes are on so no throttle for you."

Come to think of it, I think the accelerometer is directly wired to the DSC so the DME shouldn't be able to see that either if it's off...

[Phloozy]

Originally Posted by amg6975

Coding the values to the 1M values and disabling some of the additional stuff may have the net effect of mimicking the 1M DSC module but it's not "converting it." I would be shocked if the non-M unit could run the same firmware and such but I have seen weirder things. From what I know the 1M/M3 unit is quite a lot different.



This is exactly what I'm thinking. I haven't looked at the 128 wiring diagrams much but I have no idea how it would know brake pressure and wheel speed without the DSC putting them on the CAN bus. Only thing I can think is it gets brake on/off switch from the FRM and/or JBBF and says "I can't see the DSC but the brakes are on so no throttle for you."

Come to think of it, I think the accelerometer is directly wired to the DSC so the DME shouldn't be able to see that either if it's off...

I will have to try it today and run data. maybe swap the stock wheels on so I am not ruining some maxxis lol As for the tune, just testing it and same issue, brakes fully applied with throttle to the floor and no response Let him know so will see what he says next.