# High RPMs when "speed shifting"



## Aussie (Sep 16, 2012)

I have been annoyed by this in modern cars since the seventies, it has something to do with pollution control. In older cars it was mechanical and could be adjusted out, (not legal but better to drive) but with computers controlling everything it is much harder to get rid of unless you know a computer geek that is into automotive? It makes smooth driving difficult in a manual but does nothing in an automatic. It is designed to prevent sudden shut down of the gas and makes it come down slowly, and really annoys the driver.


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## obermd (Mar 3, 2012)

The ECU in my 2012 ECO MT will hold the RPMs high for a couple of seconds and I'm not tuned.


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## jblackburn (Apr 14, 2012)

The Cruze has a programmed ECU "rev hang". It sorta makes the transitions between gears a little smoother for a driver that doesn't rev match/double-clutch in between gears, but if you floor it to get in front of someone real quickly and then hold the clutch down...it just makes a lot of noise forever as the engine sloooowly winds down.

In the summer with the AC running, the rev hang doesn't work at all...the AC compressor puts a big load on the engine, so it dumps off RPMs instantly...and exacerbates turbo lag since your RPMs fell back to 1000 and the turbo was more or less entirely cut off from its exhaust supply. Kinda annoying...I've learned to keep my foot on the gas just a smidgen when running AC on fan speed 3-4 (it takes practice).


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## Hoon (Mar 18, 2012)

JB is right, there is a programmed rev hang. 

Also keep in mind, we have a tiny, low compression engine with a heavy flywheel, so even without the programming you will get some rev hang.


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## Patman (May 7, 2011)

I was starting to think I was "losing my touch" at driving a stick. Been doing it for many years and never had this problem b4. Good to hear it is normal. Besides with that small of an engine, I shouldn't be driving that way anyway! What am I going to take on an "Escort"? LOL


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## jblackburn (Apr 14, 2012)

> What am I going to take on an "Escort"? LOL


The feared & mighty Honda Civics of Suburbia.


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## Merc6 (Jun 8, 2013)

jblackburn said:


> The Cruze has a programmed ECU "rev hang". It sorta makes the transitions between gears a little smoother for a driver that doesn't rev match/double-clutch in between gears, but if you floor it to get in front of someone real quickly and then hold the clutch down...it just makes a lot of noise forever as the engine sloooowly winds down.
> 
> In the summer with the AC running, the rev hang doesn't work at all...the AC compressor puts a big load on the engine, so it dumps off RPMs instantly...and exacerbates turbo lag since your RPMs fell back to 1000 and the turbo was more or less entirely cut off from its exhaust supply. Kinda annoying...I've learned to keep my foot on the gas just a smidgen when running AC on fan speed 3-4 (it takes practice).


As for the rpm fall with a/c I blip the throttle as I slow down or come to a stop so I never start at idle rpms.


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## spacedout (Dec 7, 2010)

Hoon said:


> JB is right, there is a programmed rev hang.
> 
> Also keep in mind, we have a tiny, low compression engine with a heavy flywheel, so even without the programming you will get some rev hang.


The automatic also displays this behavior. You can easily see this when you shift in manual mode, more often than not the RPM climb slightly as you shift, dropping your more nicely into the next gear.


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