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-   -   RPM fluctuation at steady speed with DCT? (http://www.focusfanatics.com/forum/showthread.php?t=299425)

mp223 10-09-2012 09:52 AM

RPM fluctuation at steady speed with DCT?
 
I've noticed that while traveling at a steady speed, on flat, level ground the RPMs will fluctuate 50-100 RPM up and down. This happens with and without cruise control.

Is anybody else experiencing this?

foh-kuhs 10-09-2012 09:58 AM

I've noticed it going up a gentle incline at steady speed. Tach will waver a bit and you can feel it surge. I always attributed it to the engine and not the DCT but who knows.

feta_mgp 10-09-2012 10:06 AM

I don't notice this SO much, but what I have noticed since getting the 12b37 update applied to my DCT is that when using cruise control I'll have slight hiccups. The RPMs will surge often less than 100, but it's as if the car has lost power for that SPLIT second, then regains it's composure and all is well for another 20-30 seconds. I have since stopped using cruise control because it bothers/worries me. My dealership did nothing for me.

mp223 10-09-2012 10:07 AM

Quote:

Originally Posted by foh-kuhs (Post 4395212)
I've noticed it going up a gentle incline at steady speed. Tach will waver a bit and you can feel it surge. I always attributed it to the engine and not the DCT but who knows.

Well in theory, traveling at a steady speed on flat ground, the engine RPM and vehicular speed should increase or decrease linearly with consideration to gear. There "should" be no room for variations between the two.

I'm reading about something Ford calls "micro-slip." Maybe thats it?

http://www.dctfacts.com/latest-news/...ch-Europe.aspx
Quote:

Also new is the concept of clutch micro-slip, which helps reduce fuel consumption by allowing the engine to run at lower rpm, helping dampen the noise and vibration that would normally occur at such low engine speeds. Micro-slip also helps make gear shifts smoother, says Ford.
Quote:

Originally Posted by feta_mgp (Post 4395231)
I don't notice this SO much, but what I have noticed since getting the 12b37 update applied to my DCT is that when using cruise control I'll have slight hiccups. The RPMs will surge often less than 100, but it's as if the car has lost power for that SPLIT second, then regains it's composure and all is well for another 20-30 seconds. I have since stopped using cruise control because it bothers/worries me. My dealership did nothing for me.

I still notice it even when not using cruise control.

AZfocus2012 10-09-2012 11:37 AM

Micro-slip could be ford speak for shudder. Well at least it is making more sense now. Micro-slip gone wrong = shudder.


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