dsc off, car still assisting braking

[seank]

I was at Thunderhill yesterday. First time on the track in this car. I drove into turn 2 (like I do with my track car) hot while left foot braking with my foot on the gas feathering the long turn.

The car on multiple time would brake with out me pushing on the pedals. There is something going on not mentioned on this forum. A friend who is familiar with e46 m3 said that the dsc does not fully disengaged until its held down for so many seconds.

Does any experienced racers know anything about this?

[beta]

Did you take a look at this thread? In that thread there's another thread linked with explanations from The Hack.

[Finnegan]

Sean is talking about something else. This isn't about brake pedal feel, or brake assist, or air in the lines, etc.

Rather, it's some level of DSC intervening--even with DSC "off"--by braking one or more wheels when the car is getting away from you. Sean had DSC off, and yet the car still seemed to applying some corrective measures. (As he said, very hot and very fast into turn 2 at Thill.) This is similar to having DSC on in turn 2 IIRC (ran both ways in several sessions.) IIRC, Sean said he could feel it through the brake pedal (left foot resting on brake, not engaging it, but feeling it "work", right foot on throttle). I could feel it too--I could feel the car "righting" itself as if braking one or more wheels slightly.

So, the mystery here seems to be that DSC was off, but it seems there's still some threshold at which the car will intervene.

[The HACK]

The "///M" DSC only has one single mode. On or Off. Even the E46 M3, it's always been the same. Single press disables DSC. Only the Competition Package E46 M3 has multiple levels of DSC engagement, where an "M-Track Mode" is available by pressing a separate button to allow for more wheel slippage than regular DSC would allow.

Having driven multiple Competition Package equipped E46 M3s as well as the MZ4 Coupe, the DSC on the MZ4 Coupe is far more similar to the E46 M3's "track" mode allows.

I don't know if it's DSC intervening, or if the ABS is kicking in...If you're not pressing on the brake pedal and you can feel the car slowing down, then DSC is definitely still intervening. Although my experience has been otherwise, once DSC is pressed, you're on your own. A great place to test it out is actually, the banked oval portion of Auto Club Speedway. At 120+mph through turn 2, the outside wheel and the inside wheel turns at drastically different speed. Enough so that the DSC freaks out and tries to brake the outside front tire thinking you're just about to understeer into the nearest wall. Turn DSC off and the car doesn't care one way or another, even with the 15º bank and giant sweeper at 120mph.

You can press that DSC button all you want, there's no other mode to engage on the MZ4 Coupe.

[trsbmw]

Could it be DBC (Dynamic Brake Control)? I read at some point that it cannot be disabled. Since your foot was on the brake enough to feel the ABS doing something, perhaps it interpreted it as some level of braking and triggered an intervention.

[The HACK]

The ONLY other possibility I can think of, is that all modern BMWs have a built-in throttle override function where if you're on the brake AND on the gas at the same time, the ECU assumes you're attempting to brake rather than accelerate and will cut back on throttle to let the brake override your throttle command.

However, I do not believe this feature is implemented in the MZ4 Coupe, although when it's actually implemented I do not know.

[seank]

From the forum reading I did last night on the M3, it was most like the DBC. I would move over to the long left corner, feathering the gas and slightly modulating the brake (the beautiful about left foot braking) and the car would brake on its own. It was not pulses, like I have experienced in other cars or the z4m. It was actually slowing down the car more than desired, as if it was confused about my driving style.

Nonetheless, I was just curious if anyone was familiar with this. It should probably happen to someone with a DEEP trail braking. Since, it is not a track car, I won't put much thought into it.

Maybe a ghost was braking?

[Finnegan]

Originally Posted by seank

Maybe a ghost was braking?

Okay, I confess, it was me. I used my telepathic powers to modulate the brake. Can only do that at close range, so if I'm not in the car with you, you're safe.

[mfanatic325]

I've done plenty of hard trail braking into turn 2 (Andretti hairpin) @ Laguna Seca, and with DSC off, I've never noticed any undesirable braking. Everything was at my control it seemed
My guess is just the dynamic brakes effectively hugging the pads closer to the rotors in case you need to panic stop. I doubt it's that rain swiping feature, since I recall that the windshield wipers have to be triggered for it to be in effect.

[ddnmkun]

Originally Posted by The HACK

The "///M" DSC only has one single mode. On or Off. Even the E46 M3, it's always been the same. Single press disables DSC. Only the Competition Package E46 M3 has multiple levels of DSC engagement, where an "M-Track Mode" is available by pressing a separate button to allow for more wheel slippage than regular DSC would allow.

Having driven multiple Competition Package equipped E46 M3s as well as the MZ4 Coupe, the DSC on the MZ4 Coupe is far more similar to the E46 M3's "track" mode allows.

I don't know if it's DSC intervening, or if the ABS is kicking in...If you're not pressing on the brake pedal and you can feel the car slowing down, then DSC is definitely still intervening. Although my experience has been otherwise, once DSC is pressed, you're on your own. A great place to test it out is actually, the banked oval portion of Auto Club Speedway. At 120+mph through turn 2, the outside wheel and the inside wheel turns at drastically different speed. Enough so that the DSC freaks out and tries to brake the outside front tire thinking you're just about to understeer into the nearest wall. Turn DSC off and the car doesn't care one way or another, even with the 15º bank and giant sweeper at 120mph.

You can press that DSC button all you want, there's no other mode to engage on the MZ4 Coupe.

To fully turn off the DSC, remember to press and hold the DSC button for 10-12 seconds, and be 100% concentrate when you drive. To make sure its on that mode, you wont be able to turn it off unless engine is off.
Just a press on DSC does not fully disengaged DSC, but it does give amateur like me more fun on the track!

100% sure this is it on my 03 E46M, but not so sure if E86M is any different.

[Kgolf31]

Originally Posted by ddnmkun

To fully turn off the DSC, remember to press and hold the DSC button for 10-12 seconds, and be 100% concentrate when you drive. To make sure its on that mode, you wont be able to turn it off unless engine is off.
Just a press on DSC does not fully disengaged DSC, but it does give amateur like me more fun on the track!

100% sure this is it on my 03 E46M, but not so sure if E86M is any different.

This has been discussed many time, including this thread.

IT WAS IN THE POST YOU QUOTED.

It's either on/off. We don't have the stupid system that the E46 M has to go through.

[ddnmkun]

Originally Posted by Kgolf31

This has been discussed many time, including this thread.

IT WAS IN THE POST YOU QUOTED.

It's either on/off. We don't have the stupid system that the E46 M has to go through.

The "///M" DSC only has one single mode. On or Off. Even the E46 M3, it's always been the same.

I read this line from my quote and I disagree. Coz E46M isn't just ON or OFF.

Oh I know its been discuss many times, bimmerforums, M3post, M3forum, E46fanatics, all same kind of topics over and over.

[The HACK]

I have it on good authority, and you can check too if you want, that pressing the DSC for 10-12 seconds put the DSC into DIAGNOSTIC MODE, which means all the DSC features are permanently ON for diagnostic purposes and can not be manually switched off.

[psygnosis]

Originally Posted by The HACK

The ONLY other possibility I can think of, is that all modern BMWs have a built-in throttle override function where if you're on the brake AND on the gas at the same time, the ECU assumes you're attempting to brake rather than accelerate and will cut back on throttle to let the brake override your throttle command.

However, I do not believe this feature is implemented in the MZ4 Coupe, although when it's actually implemented I do not know.

I haven't tried it on a M model. But I don't see why the Z4 M or M3 wouldn't implement it. I've tested this on both an E46 and my Z4, I can rev match all day long on the street and it never kicks in, but take the car onto a lonely road press the gas and at the same time press on hard on the brake and the gas pedal will stop working. This isn't quite what the OP is describing though, you let off the brake and you can accelerate again.

[davej ff50]

I believe what is being referenced here is the engine management system overriding the driver's "request" for an open throttle position. See the attached service bulletin.

The engine management system reduces the throttle when the brakes are applied. So the ems will not allow the driver to apply the brakes and accelerator at the same time for left foot braking. This is not a function of the DSC.

"The perceptible effect for the driver creates a feeling similar to taking your foot off the accelerator pedal."

[Kgolf31]

During Autocross I drag my brakes from GRID to the starting line, and I've never experienced this.

Maybe it occurs at higher speeds?

[ga41]

If pressing both the throttle and brake pedals at the same time overrides the throttle pedal then this wouldn't be possible would it?

[ga41]

Originally Posted by Kgolf31

During Autocross I drag my brakes from GRID to the starting line, and I've never experienced this.

Maybe it occurs at higher speeds?

You're probably correct as it appears this doesn't happen at slow speeds as per the previous video and your experiences.

[psygnosis]

Just go try it out. Press the accelerator and at the same time press the brake with the intent to stop the car.

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