Getting rid of rev hang when changing gears (manual)

claasmi · 07-14-2015, 08:17 AM

When shifting gears I noticed that there is a small delay after I let of the gas before the revs start to drop. From what I've read the ECU is doing this for emissions reasons (a sudden drop in throttle will cause fuel to go unburnt). Is there any way to eliminate this via changing the ECU programming or any other way?

Ginger_Extract · 07-14-2015, 09:05 AM

What model car do you have? My N54 135i has no rev hang at all, clutch in, and the revs drop in a nice, linear movement. It's a big change coming from my Civic Si, which has rev hang and is annoying to wait for the revs to drop.

ShocknAwe · 07-14-2015, 09:16 AM

Have you done a CDV modification or delete?

swagon · 07-14-2015, 10:20 AM

This is what my N55 does as well. Apparently it's a "normal" behaviour on these engines.

claasmi · 07-14-2015, 10:28 AM

Quote:

Originally Posted by Ginger_Extract

What model car do you have? My N54 135i has no rev hang at all, clutch in, and the revs drop in a nice, linear movement. It's a big change coming from my Civic Si, which has rev hang and is annoying to wait for the revs to drop.

2011 128i. I don't think it always does it, but I only got the car recently and haven't had a lot of time yet to get concrete results of when it does or doesn't do this.

claasmi · 07-14-2015, 10:29 AM

Quote:

Originally Posted by ShocknAwe

Have you done a CDV modification or delete?

No but planning to. From what I've read CDV doesn't have anything to do with it

ShocknAwe · 07-14-2015, 10:38 AM

Yeah no idea then, mine doesn't hang as far as I've noticed.

Lucky1 · 07-14-2015, 01:12 PM

The only rev hang I have on my 128i is the delay between the time it takes for the clutch to fully engage and the rpms to dip slightly once it is engaged. After pushing in the clutch there is not much delay at all. Most noticeable when launching in 1st but observable in other gears as well.

darkrom · 07-14-2015, 03:51 PM

Quote:

Originally Posted by Ginger_Extract

What model car do you have? My N54 135i has no rev hang at all, clutch in, and the revs drop in a nice, linear movement. It's a big change coming from my Civic Si, which has rev hang and is annoying to wait for the revs to drop.

FG2 or FA5 right? The rev hang on that car OH MY GOD

haha.

Dackelone · 07-14-2015, 03:54 PM

Time for a lightened flywheel. But then... your engine may stall at times(slowing to a stop and depressing the clutch pedal).

It doesn't bother me at all. I would suggest you remove your CDV. Do a "CDV delete" mod.

07-14-2015, 08:17 AM	#1
claasmi Private 37 Rep 56 Posts Drives: 2011 128i 6MT Join Date: Jun 2015 Location: Toronto iTrader: (0) Garage List 2011 128i [0.00]	Getting rid of rev hang when changing gears (manual) When shifting gears I noticed that there is a small delay after I let of the gas before the revs start to drop. From what I've read the ECU is doing this for emissions reasons (a sudden drop in throttle will cause fuel to go unburnt). Is there any way to eliminate this via changing the ECU programming or any other way?
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07-14-2015, 09:05 AM	#2
Ginger_Extract California-bound 389 Rep 1,480 Posts Drives: BMW 135i Join Date: Jan 2013 Location: Los Angeles, CA iTrader: (3)	What model car do you have? My N54 135i has no rev hang at all, clutch in, and the revs drop in a nice, linear movement. It's a big change coming from my Civic Si, which has rev hang and is annoying to wait for the revs to drop. __________________ Streets of Willow: 1:27.7 CW 11/15/15; 1:29.5 CCW 8/15/15 \|\|\|\| Autoclub Speedway ROVAL (CCW): 1.52.6 - 12/2/17 Willow Springs - Big Willow (CW): 1:35.8 - 3/31/18 \|\|\|\| Buttonwillow #13 (CW): 1:59.3 1/27/18 https://www.facebook.com/JakeStumphRacing \|\|\|\| http://www.youtube.com/user/RaceMeMZ3
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07-14-2015, 09:16 AM	#3
ShocknAwe 1Addict 3424 Rep 8,046 Posts Drives: E82 Mutt, M57 Truck Join Date: Jul 2012 Location: Charleston iTrader: (22)	Have you done a CDV modification or delete? __________________ Daily: E82 Mutt Hauler: M57 Truck Looking for: 997/991
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07-14-2015, 10:20 AM	#4
swagon Major General 13756 Rep 8,227 Posts Drives: F80 6MT Join Date: Jun 2013 Location: . iTrader: (0)	This is what my N55 does as well. Apparently it's a "normal" behaviour on these engines. __________________
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07-14-2015, 10:38 AM	#7
ShocknAwe 1Addict 3424 Rep 8,046 Posts Drives: E82 Mutt, M57 Truck Join Date: Jul 2012 Location: Charleston iTrader: (22)	Yeah no idea then, mine doesn't hang as far as I've noticed. __________________ Daily: E82 Mutt Hauler: M57 Truck Looking for: 997/991
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07-14-2015, 01:12 PM	#8
Lucky1 Colonel 669 Rep 2,083 Posts Drives: '08 128i Coupe SGM 6MT Join Date: Nov 2008 Location: Toronto iTrader: (0) Garage List 2015 Porsche 911 Ca ... [0.00] 2006 Z4 M Roadster [0.00]	The only rev hang I have on my 128i is the delay between the time it takes for the clutch to fully engage and the rpms to dip slightly once it is engaged. After pushing in the clutch there is not much delay at all. Most noticeable when launching in 1st but observable in other gears as well.
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07-14-2015, 03:54 PM	#10
Dackelone European Editor 10759 Rep 22,992 Posts Drives: N54 e82 Join Date: Feb 2010 Location: Bayern, Germany iTrader: (1)	Time for a lightened flywheel. But then... your engine may stall at times(slowing to a stop and depressing the clutch pedal). It doesn't bother me at all. I would suggest you remove your CDV. Do a "CDV delete" mod. __________________ Dackel's European Delivery Museum Guide
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