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Old 06-19-2002, 08:14 PM   #1
quynce
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Default RPMs spike when shifting?

Had my WRX about 2 weeks now. When I shift, the RPM's go up a little. Not very dramatic from 1st-2nd, but 2nd-3rd and 3rd-4th it jumps as much as 700 rpm, sometimes less. I've been driving manuals since I got my license and have never experienced this. Is this normal? Thanks.

josh
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Old 06-19-2002, 08:50 PM   #2
Rebellion
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yeah I noticed that too... probably has something to do w/ the turbo still spinning when you put in the clutch... the sudden lack of tension bumps it up before the lack of throttle takes it back down.
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Old 06-19-2002, 09:26 PM   #3
is2scooby
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Wow! Glad I'm not the only one has noticed this! I was just too much of a little girl to open my mouth and post about it. :-)

Thought I had forgotten how to drive a stick car after slush-boxing in my IS300 for 2 years!

Wonder if a blow-off valve would help with this? Not that it's a great big problem or anything...
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Old 06-19-2002, 11:31 PM   #4
Capt Crunch
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I get the same thing. I thought it was because I pushed the gas a in a little to match the rpms better and overshot. Whatever.
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Old 06-20-2002, 07:54 AM   #5
Rebellion
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Quote:
Originally posted by is2scooby
Wow! Glad I'm not the only one has noticed this! I was just too much of a little girl to open my mouth and post about it. :-)

Thought I had forgotten how to drive a stick car after slush-boxing in my IS300 for 2 years!

Wonder if a blow-off valve would help with this? Not that it's a great big problem or anything...
i've gotta BOV .. so no it doesn't seem to help... but I'll agree somewhat with having a slow foot on the gas too. But I've noticed it when I don't even have my foot on the pedal.
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Old 06-20-2002, 08:03 AM   #6
SubEd
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Hmmm, let off the gas earlier? IIRC, it's due to the mass of the flywheel.
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Old 06-20-2002, 09:11 AM   #7
mayhem
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Quote:
Originally posted by SubEd
Hmmm, let off the gas earlier? IIRC, it's due to the mass of the flywheel.
is the mass of the flywheel on the wrx exceptionally more than most vehicles?
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Old 06-20-2002, 10:57 AM   #8
gjhsu
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Hmm, somebody asked this a few months ago, and got the reply that Subaru built it in so it can burn a little surplus fuel for some odd reason,but it's a completely normal thing so no need for worries.
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Old 06-20-2002, 12:25 PM   #9
Stanley
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I have seen this topic pop up a number of times. My car does it too. The best explanation I have heard is that, for emission purposes, modern ECU's are programmed to burn off any excess fuel in the combustion chamber rather than letting the unburned fuel travel out the exhaust system, regardless of throttle position. The fact that we have forced induction and fairly heavy flywheels may exacerbate this effect. However, in one thread I read, some guy reported that his VR6 GTI did the exact same thing.
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Old 06-20-2002, 07:46 PM   #10
quynce
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Cool. Thanks all!

671 miles. 672 miles. 673 miles. Are we there yet?

josh
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Old 06-20-2002, 10:06 PM   #11
djvapor
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Every stick I've ever driven does this. My friend asked me about it in his 3 series a couple years ago and I didn't have an answer. But, over the years I've come to the conclusion it's because the driver is still slightly on the gas when they depress the clutch. Or there is still enough gas being fed to cause the RPMs to spike.
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Old 06-21-2002, 02:45 AM   #12
Concillian
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Hmm, this happened to me when I first got my car.

I adjusted my shifting habits and it doesn't happen anymore. I think you're just staying on the gas too long.

It definitely doesn't happen to me, maybe my car is fooked then?
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Old 06-21-2002, 05:16 AM   #13
WRXTACY
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Well this happens to me also...I thought it was because my BOV. It happens on stock WRX's too? I forget when my car was stock.
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Old 06-21-2002, 10:53 AM   #14
coastguardwrx
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I noticed the same thing too switching from my honda to the wrx, but it scared me a little so I adjusted my driving so it doesn't do it anymore. I can't exactly say how, but i'll pay attention more and if I figure it out, I'll let you know. You can drive differently so it doesn't do it. Oh, my WRX is stock, so it does happen on a stock one too.

~ken
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Old 06-21-2002, 01:57 PM   #15
Stanley
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Quote:
It definitely doesn't happen to me, maybe my car is fooked then?
Yep, you better take your car into the dealer ASAP for some warranty work!

I should have clarified that technique can all but eliminate the rise in rpm's after clutching. It only happens to me if I am on the throttle and decide to short shift, like if someone unexpectedly comes into my lane and it isn't prudent to keep on boost or if I see a cop.
On my normal accelerations I may see the tach hover at the same rpm for a split second as opposed to increase a few hundred rpm's. I don't know how to explain it other than I try to "roll" on and off the throttle when changing gears as opposed to having the throttle completely open or closed.
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Old 06-21-2002, 05:42 PM   #16
KJR
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i used to notice this also, but like Concillian said, adjust your driving technique and you will notice a difference. your RPM's will spike a bit if you are a little bit on the gas or RPM's are high when you release the load from the motor.
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