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Old 11-01-2003, 01:06 PM   #1
gerbs
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Question little RPM jump while letting off gas and engaging clutch at same time??

hey guys, i've gotten my wrx's tricky manual tranny/overpowered clutch pretty much programmed into my brain now, but i have one kink to work out, which is figuring out why that when i let off the throttle and engage the clutch at the exact same time (both soft and hard clutching) there is some noticiable lag AND/OR alot of the time like 500~ rpms hop up before they begin to drop.

would possibly a grounding kit fix this issue (because it might make the throttle more responsive?)??

or should i just start letting off the throttle a little early? i'd much rather buy a grounding kit if it would actually help

also, about a grounding kit.. is it true that the 04's have better grounding wire or is that just a rumor i picked up somewhere?

has anyone else noticed this on their 04 rex??


THANKS!


(sorry for the never ending run-on sentence... F+ for me )
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Old 11-01-2003, 01:15 PM   #2
Concillian
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At first I thought it was just that my timing was off or whatever.

After getting the Utec and looking at logs it's clear that on all transitions the ECU enriches fuel for a short time to stave off detonation. In the case of shifting it's sort of an unwanted side effect, but it still helps to keep the engine from getting det.

Nothing will 'fix' it short of an aftermarket standalone ECU. You may be able to ask a n ECUtek tuner to adjust the enrichment amount/time on a reflash, but depending on how the parameters are setup in the ECU it may or may not be plausible to do so.
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Old 11-01-2003, 01:35 PM   #3
gerbs
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is there any way to help the situation without modding my ECU?
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Old 11-01-2003, 04:02 PM   #4
larryg
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It happens on my 02 also, but only on part-throttle acceleration. Drove me nuts at first but I hardly notice it anymore.

Larry
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Old 11-01-2003, 04:30 PM   #5
gerbs
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the only reason it drives me crazy is cause of the friggen rev when i change gears sometimes.. it's almost embarassing
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Old 11-01-2003, 09:31 PM   #6
hotrod
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e85forum.net

Default covered many times

This is normal for the WRX

Don't worry guys, this is completely normal, for this car. If you dig back through the list you will see it gets discussed about every 2-3 weeks on one of the forums or another.

It is a result of residual boost build up as you let off the throttle. If you make your shift just as you begin to build boost and the turbo is spooling up, when you lift the throttle, there is a sudden rise in pressure in the intercooler as the throttle begins to close. Since it takes a moment for the throttle to close, the higher pressure flows more air through the remaing opening in the throttle body.

This gives the effect of a quick blip of the throttle.

It is most obvious if you short shift around 3500-4000 rpm or so. You don't see it in more agressive shifting because the boost increase is enough to pop the BOV, and in low speed shifting the turbo has not started to spool significantly and your shifts are usually slower (gives more time for the throttle to close so less pressure rise)

It is easy to deal with, just lift on the throttle a fraction of a second before you start your shift. That way when you press the clutch in and unload the engine, the boost increase has already disappeared.

Larry


http://forums.nasioc.com/forums/show...residual+boost
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Old 11-01-2003, 11:15 PM   #7
wbwrx
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you tps could be going bad. that is what mine is doing so you looked at the scaner and it showed that the tps was bad
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Old 11-01-2003, 11:19 PM   #8
AndyWRXWG
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that's weird I was just having that happen to me tonight and was wondering what the hell was going on. I've noticed it before, but for some reason tonight it just kind of hit me and I was questioning it. wierd.....
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Old 11-01-2003, 11:36 PM   #9
gerbs
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Wink

maybe its the chicagoy rains that are getting to our scoobies


what = tps?
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Old 11-02-2003, 01:06 AM   #10
wbwrx
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what = tps?

throttle position sensor
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Old 11-02-2003, 01:09 AM   #11
gerbs
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ic.

so a grounding kit is deemed useless in this situation?

and does anyone know if the grounds are better on 2004 wrxs??

thanks for all the replys guys! it's very appreciated
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Old 11-02-2003, 01:27 AM   #12
wbwrx
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my 02 is grounded and it dose not help
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Old 11-02-2003, 03:21 AM   #13
totoherbs
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Quote:
Originally posted by hotrod
This is normal for the WRX

Don't worry guys, this is completely normal, for this car. If you dig back through the list you will see it gets discussed about every 2-3 weeks on one of the forums or another.

It is a result of residual boost build up as you let off the throttle. If you make your shift just as you begin to build boost and the turbo is spooling up, when you lift the throttle, there is a sudden rise in pressure in the intercooler as the throttle begins to close. Since it takes a moment for the throttle to close, the higher pressure flows more air through the remaing opening in the throttle body.

This gives the effect of a quick blip of the throttle.

It is most obvious if you short shift around 3500-4000 rpm or so. You don't see it in more agressive shifting because the boost increase is enough to pop the BOV, and in low speed shifting the turbo has not started to spool significantly and your shifts are usually slower (gives more time for the throttle to close so less pressure rise)

It is easy to deal with, just lift on the throttle a fraction of a second before you start your shift. That way when you press the clutch in and unload the engine, the boost increase has already disappeared.

Larry


http://forums.nasioc.com/forums/show...residual+boost


Ive seen it talked about 3 or 4........ dozen times.
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