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01-09-2013, 07:42 PM | #1 |
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M drive rev match
I am new to my M3 so I thought I would ask the experts. I use my car as a DD. I drive around it auto mode, normal, comfort.
Question why does some times the car just downshifts like a normal auto car and other times when it is downshifting it rev matches like it does when I am in S mode racing around. It seems like it just does it randomly as well. I have tried to get it to do it and I can't and then it just does it other times. Thanks
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01-09-2013, 08:21 PM | #2 |
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I kind of chalked it up to based on the speed I was decelerating. But sometimes it's just random based on your pedal inputs.
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01-09-2013, 08:40 PM | #4 |
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Doesn't every automatic transmission rev match downshift every time? Isn't that the whole point?
Are you saying that sometimes it downshifts slowly while other times it does more briskly? |
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01-09-2013, 08:56 PM | #5 |
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I am saying that most times to just downshifts normally like my Lexus and other times when it downshifts the rpm's rev way up. I am sorry I am not explaining it well.
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01-10-2013, 02:28 AM | #6 |
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I noticed it tends to rev-match if you downshift when your foot is on the gas pedal / if you're accelerating slightly, or maybe if you've been driving aggressively. If you're just coasting / braking to a stop, it doesn't.
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01-10-2013, 04:04 AM | #7 |
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I know exactly what you mean. It really depends on how fast you decelerate
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01-10-2013, 05:07 AM | #8 | |
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My conclusion is the same. DCT will rev match if your foot is on the throttle even in S1, S2 or S3. I actually use this feature as I usualy use S2 on my DD. If I want a quick downshift while braking, I blip the throttle with the heel and toe technique and I get a nice and quick rev matched downshift . This behavior of the DCT seems to be part of the software fix for the DCT lag issue, as the car did not behave that way when I originaly got it in 2008. |
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01-10-2013, 07:06 AM | #9 |
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ok now im lost. Heel toe with DCT? What is the point of that? Why would you want one foot hitting the gas and brake at the same time? If you want the car to downshift, simply use the paddles or shift lever.
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01-10-2013, 08:47 AM | #10 | |||
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01-10-2013, 10:52 AM | #11 |
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Does the DCT really ride the clutch plate during downshifts? I figured every downshift would be rev matched to extend the life of those oh so expensive wear items...
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01-10-2013, 11:42 AM | #13 | |
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It is not something I do often but it is useful in some specific occasions. There is a significant delay from when you pull the paddle to when the downshift happens in the lower Drivelogic modes and the downshift itself is pretty slow. No need for heel and toe in S4 to S6 modes . Last edited by CanAutM3; 01-10-2013 at 06:24 PM.. |
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01-10-2013, 11:46 AM | #14 | |
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Even if I brake hard, my DCT will not rev match in S1 or S2. The only way I can get it to rev match in those modes is to blip the throttle . |
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01-10-2013, 11:49 AM | #15 | |
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The wear on downshifts is nothing compared to the wear on full throttle upshifts. Last edited by CanAutM3; 01-10-2013 at 06:26 PM.. |
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01-10-2013, 12:39 PM | #16 |
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Sorry, just caught that. heel/toe
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01-10-2013, 09:46 PM | #17 | |
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01-12-2013, 10:43 PM | #18 | |
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01-12-2013, 10:54 PM | #19 |
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Up-shifting or down-shifting, there is similar amount of clutch slip (assuming similar shift times). However, on a full throttle upshift, there is much more force (torque) transmitted through the clutch, hence more wear.
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01-13-2013, 03:07 AM | #20 |
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Yep, noticed this too in the last couple days. Still surprises me sometimes when I'm in M mode (S5 for me) and I downshift mindlessly when I'm slowing to a stop. I think it's my favorite feature right now. So aggressive
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01-13-2013, 05:57 AM | #21 | |
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Being stuck in traffic and slow shifts in lower modes would have more clutch slip and wear on the discs. Other than launch control, high rpm shifts in S1-S2 (maybe auto mode too) should have the most slip and wear on the clutch discs. |
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01-13-2013, 07:20 AM | #22 | |
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As an example, think of sanding a surface. If you don't apply much force, you are not removing much material with each pass and you need to sand longer. However if you increase the force, more material gets removed much faster, i.e. more wear. The worst case would be a long clutch engagement time with high forces being trasmitted. As you stated, launch control is an example where the clutch slips while the engine is at max power. |
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