Engine revs up during downshift (D2)

-cj- · 12-13-2013, 07:46 PM

Hi folks,

E90 M3 is acting up. Upon (somewhat hard) braking to a stop, while driving in drive logic 2, in auto mode, the car will shift from D7 to D2-D3 but it will rev up, almost like a rev match, before engaging the gear. RPMs will shoot up to like 4-5k and then back down, almost like I blipped the throttle.

Anyone ever experience this? Days ago, the wife told me it does that often when she's driving. I had the car in D5 mode at that time and explained to her it was rev matching and was intended... But today I noticed it in D2, which is definitely not supposed to happen. We also had a low battery charge warning during a pit stop, so it might be an electrical issue? (It was very cold out, first and only time I've seen that warning though...)

Thoughts?

Edit: I went to drive logic 1, and it didn't do it. I went back to 2 and it wouldn't do it again either... Doesn't seem right!

dparm · 12-13-2013, 09:07 PM

I noticed this kind of thing on several M3s that I drove, and mine does it a bit too. The computer is a bit weird when you're coming to a halt like that. I don't really know why, but I wouldn't worry about it unless there is noticeable drivetrain shock.

-cj- · 12-13-2013, 10:27 PM

Thanks Dan. The weird thing is, I tried to repeat this in drive logic 2 and it did it 2-3 more times, every time I tried to duplicate it. Then I went to drive logic 1 and could not replicate. Went back to 2 and it went away! Seems strange!

jra85 · 12-13-2013, 11:21 PM

If you're describing what I think, I see it happen even in manual mode when the transmission automatically downshifts as the car's slowing. It'll shift from 4th (or higher) to 2nd and the revs increase, similar to as if you were driving a manual transmission and downshifted without applying throttle or matching first (engine braking). Is this what you're observing?

I've scared myself a few times by hitting the throttle as the transmission auto-downshifts to 2nd and it rev matches unexpectedly (and the downshift to 2nd always gives a nice one

)

aussiem3 · 12-14-2013, 03:04 AM

Quote:

Originally Posted by -cj-

Hi folks,

E90 M3 is acting up. Upon (somewhat hard) braking to a stop, while driving in drive logic 2, in auto mode, the car will shift from D7 to D2-D3 but it will rev up, almost like a rev match, before engaging the gear. RPMs will shoot up to like 4-5k and then back down, almost like I blipped the throttle.

Anyone ever experience this? Days ago, the wife told me it does that often when she's driving. I had the car in D5 mode at that time and explained to her it was rev matching and was intended... But today I noticed it in D2, which is definitely not supposed to happen. We also had a low battery charge warning during a pit stop, so it might be an electrical issue? (It was very cold out, first and only time I've seen that warning though...)

Thoughts?

Edit: I went to drive logic 1, and it didn't do it. I went back to 2 and it wouldn't do it again either... Doesn't seem right!

What do you expect when you downshift from 7 to 2/3 regardless whether you are slowing down or not, you are going to increase engine speed ... bit like trying an engine brake.

-cj- · 12-14-2013, 03:54 PM

Sorry I should have mentioned that I wasn't going very fast. I was probably at 1.5k rpm in 7th and already rolling to a stop. I just decided to induce this downshift behavior after I spotted it, and I could repeat it several times.

The key thing is, it stopped doing this after some point. So it does not seem normal. I drive regular MTs every day, this isn't regular down shifting. I was also being generous when I said 4-5k RPM, it shoots up to like 6+ rpm and quickly comes down because it engages the gear.

If this were a MT, if you were on the brake and rolled your foot to blip the throttle (while holding in the clutch), but were too aggressive and brought it up to 6k+ rpm and then released the clutch, this is what this feels like. It is not a perfrect rev match. (It shouldn't even be rev matching in drive logic 2)

12-13-2013, 07:46 PM	#1
-cj- Captain 198 Rep 799 Posts Drives: '20 X5MC \| '20 Z4 Join Date: Dec 2011 Location: Toronto iTrader: (3)	Engine revs up during downshift (D2) Hi folks, E90 M3 is acting up. Upon (somewhat hard) braking to a stop, while driving in drive logic 2, in auto mode, the car will shift from D7 to D2-D3 but it will rev up, almost like a rev match, before engaging the gear. RPMs will shoot up to like 4-5k and then back down, almost like I blipped the throttle. Anyone ever experience this? Days ago, the wife told me it does that often when she's driving. I had the car in D5 mode at that time and explained to her it was rev matching and was intended... But today I noticed it in D2, which is definitely not supposed to happen. We also had a low battery charge warning during a pit stop, so it might be an electrical issue? (It was very cold out, first and only time I've seen that warning though...) Thoughts? Edit: I went to drive logic 1, and it didn't do it. I went back to 2 and it wouldn't do it again either... Doesn't seem right! Last edited by -cj-; 12-13-2013 at 10:26 PM..
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12-13-2013, 09:07 PM	#2
dparm Stop the hate, get a V8 3850 Rep 8,625 Posts Drives: C7 Corvette GS, AMG C63 S Join Date: Jun 2013 Location: Frisco, TX iTrader: (1)	I noticed this kind of thing on several M3s that I drove, and mine does it a bit too. The computer is a bit weird when you're coming to a halt like that. I don't really know why, but I wouldn't worry about it unless there is noticeable drivetrain shock. __________________ Now: 2017 Corvette Grand Sport, 2021 AMG C63 S sedan Past: 2011.5 M3 sedan ZCP
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12-13-2013, 10:27 PM	#3
-cj- Captain 198 Rep 799 Posts Drives: '20 X5MC \| '20 Z4 Join Date: Dec 2011 Location: Toronto iTrader: (3)	Thanks Dan. The weird thing is, I tried to repeat this in drive logic 2 and it did it 2-3 more times, every time I tried to duplicate it. Then I went to drive logic 1 and could not replicate. Went back to 2 and it went away! Seems strange!
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12-13-2013, 11:21 PM	#4
jra85 M3NTAL 132 Rep 608 Posts Drives: 2011 E92 M3 ZCP Join Date: May 2010 Location: Long Island, NY iTrader: (1)	If you're describing what I think, I see it happen even in manual mode when the transmission automatically downshifts as the car's slowing. It'll shift from 4th (or higher) to 2nd and the revs increase, similar to as if you were driving a manual transmission and downshifted without applying throttle or matching first (engine braking). Is this what you're observing? I've scared myself a few times by hitting the throttle as the transmission auto-downshifts to 2nd and it rev matches unexpectedly (and the downshift to 2nd always gives a nice one )
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12-14-2013, 03:54 PM	#6
-cj- Captain 198 Rep 799 Posts Drives: '20 X5MC \| '20 Z4 Join Date: Dec 2011 Location: Toronto iTrader: (3)	Sorry I should have mentioned that I wasn't going very fast. I was probably at 1.5k rpm in 7th and already rolling to a stop. I just decided to induce this downshift behavior after I spotted it, and I could repeat it several times. The key thing is, it stopped doing this after some point. So it does not seem normal. I drive regular MTs every day, this isn't regular down shifting. I was also being generous when I said 4-5k RPM, it shoots up to like 6+ rpm and quickly comes down because it engages the gear. If this were a MT, if you were on the brake and rolled your foot to blip the throttle (while holding in the clutch), but were too aggressive and brought it up to 6k+ rpm and then released the clutch, this is what this feels like. It is not a perfrect rev match. (It shouldn't even be rev matching in drive logic 2)
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