DCT: What to do in case of a stuck accelerator.

[r53s65e90]

Those who have DCT may have wondered what they should do in case you car becomes a Toyota and starts accelerating for you. I decided to find out.

I simulated a stuck throttle by fully pressing the throttle with my right foot with 7th gear engaged going about 65mph. Then I tried to put the car in neutral. It doesn't go to neutral if there is load on the engine. Then I pressed the brake pedal with my left foot while still pressing the throttle with my right foot. Then I held the lever on then N position (all the way to the left). This worked: the car went to N and the revs bounced off the limiter.

So when the accelerator sticks for any reason apply the break and hold the lever to N.

I didn't try (and I won't) to hold the start button for a long period.

[FruitCake]

good to know if a Toyota hacks my DME lolz

[gtr]

My friend has an evo MR with twin clutch overseas with bad quality gas. His car stalled and 4 wheel lockup at highway speed and crashed! Don't try to turn the car off. There is no torque converter to coast to a stop.

good to know that putting the car in neutral under load doesn't work w/o applying the brakes

[Krozi]

Push in the clutch....oh yea...that's right.....

[M3Alpine]

[zuggerat89]

Originally Posted by Krozi

Push in the clutch....oh yea...that's right.....

[M3Bliss]

Originally Posted by gtr

My friend has an evo MR with twin clutch overseas with bad quality gas. His car stalled and 4 wheel lockup at highway speed and crashed! Don't try to turn the car off. There is no torque converter to coast to a stop.

If you perform the trick of foot on the brake (or break )/neutral then you could turn the car off and it would drift to a stop. That's a lot of operations though and by that time you could be having lunch with St. Peter.

[BPMSport]

Holding down the start button will take care of turning the car off. Depends how badly you need power steering / braking.

[Bald Guy]

Interesting topic.

[smmmurf]

Originally Posted by Krozi

Push in the clutch....oh yea...that's right.....

[JC919]

Tuck your head between you legs and kiss your ass good bye.

[EJ_92606]

Originally Posted by TrackRat

There should be an override so that when you press the brake and accelerator for like 5 seconds the engine returns to neutral regardless of where the thottle pedal is if the vehicle is in motion above a minimum speed.

There is...if you are hard on the brake and gas, fuel will be cut. This applies to all recent model BMWs.

[JCtx]

No need for any tricks folks: brakes will always overpower the engine on a modern car, so just mash the brake, keep driving, and car will stop not much longer than if you didn't have any throttle, like a recent major car magazine (MT?) proved. The Camry/Lexus ES just took 10' longer. Worse offender was a supercharged 550+ HP 'stang (with crappy stock brakes), but stopped with no drama. All those folks reaching over 100 mph on Priuses, Camrys, etc., should have taken driving lessons. And a few of those should have been thrown to jail for trying to scam their way to a new car. Crazy.

[gr8000]

Originally Posted by gtr

My friend has an evo MR with twin clutch overseas with bad quality gas. His car stalled and 4 wheel lockup at highway speed and crashed! Don't try to turn the car off. There is no torque converter to coast to a stop.

WHAT? This is bloody dangerous!

I hope there is some sort of failsafe system that disengages the clutch in case of power failure, otherwise it will be a hell of a situtuation one will be in if power is lost at higher speeds (eg in the highway).

Does any of our BMW insiders / experts have any info on this?

[spyderco10]

i think in at least some of those "stuck accelerator" cases, the drivers were actually mashing the gas pedal mistaking it for the brakes. if this was the case, of course the car wouldn't stop.

across the street from where i work, this elderly couple driving through the parking lot accidentally stomped on the gas pedal (thinking it was the brakes apparently), and drove through a hollow tile wall. literally. half the car ended up on the other side of the wall. it was a acura service area on the other side of the wall and thank God there was nobody there at the time, or the person/people could have gotten hurt or killed.

[sehrgut]

Originally Posted by Krozi

Push in the clutch....oh yea...that's right.....

SIGH

[Tony B]

Originally Posted by gtr
My friend has an evo MR with twin clutch overseas with bad quality gas. His car stalled and 4 wheel lockup at highway speed and crashed! Don't try to turn the car off. There is no torque converter to coast to a stop.

Originally Posted by gr8000

WHAT? This is bloody dangerous!

I hope there is some sort of failsafe system that disengages the clutch in case of power failure, otherwise it will be a hell of a situtuation one will be in if power is lost at higher speeds (eg in the highway).

Does any of our BMW insiders / experts have any info on this?

I cannot believe this.

Lifting off the gas to a fully closed throttle cuts off all fuel to the engine on any modern car (above about 1000rpm, anyway). Whats the difference between that and stalling?

If the engine had seized - rather than stalled - then you might have a problem, but DCT/DSC is designed to declutch if traction is lost on the over-run. Maybe Japanese manufacturers do not design in the same level of sophistication as BMW, but I doubt it. The Mitsubishi has active yaw control, for example.

Something else going on here.

[mkoesel]

Originally Posted by gtr

My friend has an evo MR with twin clutch overseas with bad quality gas. His car stalled and 4 wheel lockup at highway speed and crashed! Don't try to turn the car off. There is no torque converter to coast to a stop.

Wait, what?

What gear was he in? Did the transmission automatically drop to 2nd gear or something? I don't understand why the hell the wheels would lock up.

[mkoesel]

Originally Posted by r53s65e90

Those who have DCT may have wondered what they should do in case you car becomes a Toyota and starts accelerating for you. I decided to find out.

I am pretty certain that all BMWs have a throttle lock out. If you were to jam the brake to the floor, the throttle should cut completely, and the car will thus slow down and come to a stop. So you can just pull off the road and shut it down.

[gr8000]

Originally Posted by Tony B

Lifting off the gas to a fully closed throttle cuts off all fuel to the engine on any modern car (above about 1000rpm, anyway). Whats the difference between that and stalling?

Difference is no brakes and no steering assistance. Pretty scary if you ask me.

In addition, depending on the speed & gear (and assuming no auto de-clutching in case of power failure) you could end up with wheel lock up. This is because lifting off the gas does not fully cut all fuel, if it did the engine would be off. There is minimal fuel injected so the engine runs. This is much different as oposed to a power failure with no fuel combustion - in the latter case you have the full engine compression (and component friction) producing significantly higher engine braking.

[MysticBlue]

Originally Posted by gr8000

WHAT? This is bloody dangerous!

I hope there is some sort of failsafe system that disengages the clutch in case of power failure, otherwise it will be a hell of a situtuation one will be in if power is lost at higher speeds (eg in the highway).

Does any of our BMW insiders / experts have any info on this?

These clutches are normally disengaged. It takes hydraulic pressure to engage them. Engine not running > clutch disengaged. Feel better? In any case, I really don't see any difference between lifting on the throttle and the engine ignition being shut off or whatever else causes the engine to stop running. It's not going to lock up the wheels even if the clutch stays engaged. (Obviously, a siezed engine is a whole 'nother story). Considering the black box knows enough to disengage the clutch in a spin, my guess is the BMW engineers have taken these possibilities into account.
I'm sure there's more to the story regarding that evo than a simple engine stall causing the wheels to lock up. (No, I'm not an insider or an expert).