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      02-23-2015, 07:44 PM   #1
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Odd 6mt observations - advice

Is the following behavior normal on a 6mt? Hope some experts could shed some light, or warn me of impending doom...

When rolling at 10+ mph with the stick in neutral, foot off the clutch pedal, if I push the accelerator (eg to rev match) the responsiveness is very laggy and slow. It takes more accel pedal and holding it for longer to get the rpm's to rise

If im rolling at 10+ mph, stick in neutral, but clutch fully depressed, pressing the accel pedal results in nicer snappier revs, more responsiveness.

When fully stopped, or rolling <3mph, revs are also nice and snappy in neutral.

I don't remember past vehicles responding sluggishly when revving while rolling...

'07 6mt 111k miles original clutch and fly

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      02-24-2015, 10:54 AM   #2
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Quote:
Originally Posted by Jklad View Post
Is the following behavior normal on a 6mt?
I've never noticed anything like this on my car. I'll try the specific combinations you described today and see if I notice anything.

I don't think this is a transmission issue. It's got to be DME related somehow.
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      02-24-2015, 11:12 AM   #3
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Pretty sure the throttle mapping is changed in neutral. If you miss a gear and get back on the gas it helps from over reving.
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      02-24-2015, 12:14 PM   #4
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That's strange indeed. My 6MT exhibits no such issues :/ How is it when flooring it in gear, clutch pedal untouched?
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      02-24-2015, 12:29 PM   #5
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Quote:
Originally Posted by Jklad View Post
When rolling at 10+ mph with the stick in neutral, foot off the clutch pedal, if I push the accelerator (eg to rev match) the responsiveness is very laggy and slow. It takes more accel pedal and holding it for longer to get the rpm's to rise

If im rolling at 10+ mph, stick in neutral, but clutch fully depressed, pressing the accel pedal results in nicer snappier revs, more responsiveness.

When fully stopped, or rolling <3mph, revs are also nice and snappy in neutral.

I don't remember past vehicles responding sluggishly when revving while rolling...

'07 6mt 111k miles original clutch and fly

Thanks
My 2007 6MT is exactly the same. No problems.
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      02-24-2015, 12:54 PM   #6
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Yep, noticed the same thing. The 6MT ECU has a few different things. Holding the throttle open between shifts when aggressively driving to not bleed as much boost off is another one of them.
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      02-24-2015, 02:14 PM   #7
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Do you think it has to do with the engine spinning just the DMF (neutral w/ clutch depressed) vs the DMF,Clutch, Input Shaft in transmission (neutral w/ foot off clutch).

That may explain why it is revving slower due to more rotating mass

"When fully stopped, or rolling <3mph, revs are also nice and snappy in neutral." - is your clutch depressed at this point?
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      02-24-2015, 02:23 PM   #8
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Exact same thing with my 07 e92. I'm glad you mentioned it.
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      02-24-2015, 03:16 PM   #9
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Quote:
Originally Posted by dbworld4k
That's strange indeed. My 6MT exhibits no such issues :/ How is it when flooring it in gear, clutch pedal untouched?
It seems ok, aside from a small occasional hesitation when initially pushing the accel pedal >40% (could be unrelated, idk)
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      02-24-2015, 03:24 PM   #10
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Quote:
Originally Posted by Tim603
Do you think it has to do with the engine spinning just the DMF (neutral w/ clutch depressed) vs the DMF,Clutch, Input Shaft in transmission (neutral w/ foot off clutch).

That may explain why it is revving slower due to more rotating mass

"When fully stopped, or rolling &lt;3mph, revs are also nice and snappy in neutral." - is your clutch depressed at this point?
Nope, in this example clutch is not pressed at all, stick in neutral.
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      02-24-2015, 03:25 PM   #11
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Hmmm...in my examples I'm not driving aggressively.
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      02-24-2015, 03:28 PM   #12
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Quote:
Originally Posted by Tim603
Do you think it has to do with the engine spinning just the DMF (neutral w/ clutch depressed) vs the DMF,Clutch, Input Shaft in transmission (neutral w/ foot off clutch).

That may explain why it is revving slower due to more rotating mass

"When fully stopped, or rolling &lt;3mph, revs are also nice and snappy in neutral." - is your clutch depressed at this point?
This could explain it, I didn't realize there's more going on mechanically with stick in neutral and clutch fully out, as compared to clutch pedal fully pressed. I think I learned something!!!

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      02-24-2015, 03:40 PM   #13
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Same thing in my car. It annoys the living piss out of me. And I'm running the spec steel smfw.
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      02-24-2015, 05:53 PM   #14
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Same here ! 2009 335xi 115k km (around 71500mi) on original clutch and flywheel.
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      02-24-2015, 07:47 PM   #15
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when you let go of the clutch pedal (foot off), stick in neutral, the engine is still connected to the tranny. But the tranny is in neutral internally. But that doesn't mean the engine isn't under some load. The engine is still spinning a neutral gear inside the tranny which puts a load on the motor.

Now when you depress the clutch (foot pushed down, no matter what position the stick is in, now the engine is fully disengaged from the tranny. So the engine technically has no load applied to it from the tranny, other than the mass of the flywheel. hence, that's why it will be easy for the engine to rev up faster.
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      02-25-2015, 12:19 AM   #16
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Quote:
Originally Posted by C.Pop View Post
The 6MT ECU has a few different things. Holding the throttle open between shifts when aggressively driving to not bleed as much boost off is another one of them.
It does that by cutting ignition timing so it doesn't have to open the waste gates as much to maintain boost. I've posted this several times but the 6AT guys refuse to believe it (even though I posted the info from a SAE paper by BMW engineers).

I did a QUICK test today and really didn't notice a difference clutch in/clutch out.

I'll try again tomorrow.
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      02-25-2015, 01:16 AM   #17
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I don't know about the timing, but I have logs showing the ECU just holding the throttle position wide open/slowly drifting closed with foot off of pedal. Cool feature.
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      02-25-2015, 09:43 AM   #18
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Quote:
Originally Posted by NoTempoLimitN54
Quote:
Originally Posted by C.Pop View Post
The 6MT ECU has a few different things. Holding the throttle open between shifts when aggressively driving to not bleed as much boost off is another one of them.
It does that by cutting ignition timing so it doesn't have to open the waste gates as much to maintain boost. I've posted this several times but the 6AT guys refuse to believe it (even though I posted the info from a SAE paper by BMW engineers).

I did a QUICK test today and really didn't notice a difference clutch in/clutch out.

I'll try again tomorrow.
Try it when rolling at around 20-30mph. When you put in n, let the revs fall to 800 before revving it.
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