DCT behavior at stop light

ferocity02 · 02-20-2019, 04:27 PM

I've read a couple threads that say when I come to a stop in a DCT transmission car, that the DCT should disengage the clutch. When I release the brake the car should not move until I start to give it throttle at which point the clutch will start engaging. Does that sounds correct?

My 2013 135is does not do that. When I release the brake it begins rolling forward just like an automatic. However, the onset of the roll is much slower and gentler than an automatic. When I release the brake it feels like the clutch starts to engage. If I then give it gas it seems to engage faster.

How should it be operating?

RSL · 02-20-2019, 05:23 PM

It's a difference between an M and non-M. M DCT does not engage the clutch until you press the accelerator. Non-M DCT will "engage" with brake release, though it may technically operate under the drive off assist logic. Drive off assist on an M DCT is that it simply holds the brakes for up to 2 secs so the car doesn't roll between releasing the brake and stepping on the accel. M-DCT is a total pain in stop/go/creeping traffic scenarios, non-M way is much less annoying.

DerekGates · 02-20-2019, 07:27 PM

Quote:

Originally Posted by RSL

It's a difference between an M and non-M. M DCT does not engage the clutch until you press the accelerator. Non-M DCT will "engage" with brake release, though it may technically operate under the drive off assist logic. Drive off assist on an M DCT is that it simply holds the brakes for up to 2 secs so the car doesn't roll between releasing the brake and stepping on the accel. M-DCT is a total pain in stop/go/creeping traffic scenarios, non-M way is much less annoying.

Oh? You think the M-DCT is a pain in creeping situations? That bothers me; I was going to put in the M3 rear diff to enable M-DCT software in my 335is as the creeping in the 335is bothers me... oh boy.

RSL · 02-20-2019, 09:40 PM

Yeah, I posted about it and the FD in that thread. It's actually one of the reasons I sold the M3 lol It didn't bother me for a long time, but once it did, there was no ignoring it. Slow moving wasn't a real problem. Stop and then having to press the pedal to move 15 feet at a time every couple seconds for 5-10 miles twice a day, 5 days a week drove me insane after a while. I almost didn't even look at the 335is DCT because of it, but the FD and engagement was much better for me.

Every one/situation/use/goals are different and some might not even notice or care. The M setup/drive logic is lightyears better than non-M DCT. My situation is totally different now and I'd do the swap knowing full well what it's like at this point (with a 2.81 instead of the 3.15), but not sure I'll stay in it long enough to make it worthwhile.

fastboatster · 12-25-2019, 07:23 PM

Sounds like m dct behaves almost like a manual, and probably needs to be driven like one in traffic. I.e., don't sit on the rear bumper of the car in front of you, let it move more than 10-15 feet, ideally, leave 3 car lengths between you and them so that you have to stop less. Will save you some clutch wear, too.

02-20-2019, 04:27 PM	#1
ferocity02 Colonel 530 Rep 2,083 Posts Drives: 2013 135is Join Date: May 2014 Location: USA iTrader: (8)	DCT behavior at stop light I've read a couple threads that say when I come to a stop in a DCT transmission car, that the DCT should disengage the clutch. When I release the brake the car should not move until I start to give it throttle at which point the clutch will start engaging. Does that sounds correct? My 2013 135is does not do that. When I release the brake it begins rolling forward just like an automatic. However, the onset of the roll is much slower and gentler than an automatic. When I release the brake it feels like the clutch starts to engage. If I then give it gas it seems to engage faster. How should it be operating? __________________ 2013 135is DCT Carbon Black Metallic
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02-20-2019, 05:23 PM	#2
RSL Captain 647 Rep 779 Posts Drives: E92 ///M3 (Retired) / 335is Join Date: Mar 2012 Location: USA iTrader: (6)	It's a difference between an M and non-M. M DCT does not engage the clutch until you press the accelerator. Non-M DCT will "engage" with brake release, though it may technically operate under the drive off assist logic. Drive off assist on an M DCT is that it simply holds the brakes for up to 2 secs so the car doesn't roll between releasing the brake and stepping on the accel. M-DCT is a total pain in stop/go/creeping traffic scenarios, non-M way is much less annoying.
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02-20-2019, 09:40 PM	#4
RSL Captain 647 Rep 779 Posts Drives: E92 ///M3 (Retired) / 335is Join Date: Mar 2012 Location: USA iTrader: (6)	Yeah, I posted about it and the FD in that thread. It's actually one of the reasons I sold the M3 lol It didn't bother me for a long time, but once it did, there was no ignoring it. Slow moving wasn't a real problem. Stop and then having to press the pedal to move 15 feet at a time every couple seconds for 5-10 miles twice a day, 5 days a week drove me insane after a while. I almost didn't even look at the 335is DCT because of it, but the FD and engagement was much better for me. Every one/situation/use/goals are different and some might not even notice or care. The M setup/drive logic is lightyears better than non-M DCT. My situation is totally different now and I'd do the swap knowing full well what it's like at this point (with a 2.81 instead of the 3.15), but not sure I'll stay in it long enough to make it worthwhile.
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12-25-2019, 07:23 PM	#5
fastboatster Captain 382 Rep 890 Posts Drives: 2009 bmw 328i Join Date: May 2019 Location: CA iTrader: (0)	Sounds like m dct behaves almost like a manual, and probably needs to be driven like one in traffic. I.e., don't sit on the rear bumper of the car in front of you, let it move more than 10-15 feet, ideally, leave 3 car lengths between you and them so that you have to stop less. Will save you some clutch wear, too.
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