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Old 03-21-2007, 10:13 PM   #1
racerX_244
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Default RPM Surge, Bypass valve not functioning?

i've got an '03 wrx. seems like when i get into boost when its warm, and go to shift (clutch in, letting out the throttle to grab the next gear) i get a ~500rpm surge, almost as if the blow off valve isn't releasing the boost pressure, and its pushing the throttle body open. its in the same "burst" that a blow off would be as well.

Would a vacuum line issue be causing this? the blow off valve not getting a vacuum signal and opening up when it should? faulty valve? I'm new to subarus, but i've built custom turbo projects in the past. no mods, factory boost gauge tee'd into the vacuum hose coming off the blow off valve.

let me know if this is normal. thanks
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Last edited by racerX_244; 03-22-2007 at 03:06 AM.
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Old 03-21-2007, 10:52 PM   #2
firebox40dash5
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It's normal. Srsly.
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Old 03-21-2007, 10:56 PM   #3
bdpAKAknox
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The bov being in existence would cause that problem.
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Old 03-22-2007, 12:00 AM   #4
ErasureWRX
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Quote:
Originally Posted by firebox40dash5 View Post
It's normal. Srsly.
It is. The only real problem is that you have a BOV
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Old 03-22-2007, 03:00 AM   #5
racerX_244
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BOV, BPV, sorry if i'm not explaining it right. its the stock "bypass valve." not some xs power blow off or something. its all stock. this is where my confusion hits.

so its normal to run at wot until 7k, then go to shift and watch the tach spin further after i lift off the gas, and not hear the stock bypass valve? I understand its not supposed to be a noisy vrrrm-pshhh ricer blow off valve. i've driven other subarus, and I could at least faintly hear their bypass valve.

guess i'll just start checking vacuum lines and the blowoff valve itself. thanks guys...
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Old 03-22-2007, 10:53 AM   #6
Force
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^^you have to adjust your shifting techniques to compensate for this. This is normal on our cars, especially while under more load. More load = more throttle = turbo spooling = rpm spike when you quickly let off the gas. Let off the gas for a brief second and then clutch in to avoid this. It happens to me everyday at least a couple of times. I've learned to shift at 7K RPM so this does not happen, you just have to get to know how your car responds a little better. When I first got the car, this happened to me all the time at WOT...at first I thought it was the car, but it's somewhat the driver's technique as well.
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Old 03-22-2007, 02:41 PM   #7
racerX_244
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thanks wrxgon. this makes sense, as its not a constant thing. guess its something i'll have to get used to.

sorry for sounding ignorant, just really like my car and wanting to make sure i don't have something wrong.

the previous owner, for some reason, had a one way check valve in the vacuum line heading to the factory boost gauge. right after the bov. i took off the valve and found that it must be blown out, since it will allow vacuum or pressure to pass through either end. was this some sort of band aid fix for the surging i wonder? if it was it didn't work.

either way, thanks for the advice. guess i'll just have to learn to not drive like a noob.
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Old 03-22-2007, 03:19 PM   #8
ErasureWRX
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This bothered me at first, too, but sadly it's just normal
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Old 03-22-2007, 03:50 PM   #9
aps2fast4u
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Yep, normal. Happens on most forced induction cars I believe.
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