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Old 01-30-2013, 11:24 AM   #1
rdieder
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Default Big turbo guys, why VTA BOVs over recircualting BPVs?

Why do all you big turbo guys choose a vent to air style BOV rather than an aftermarket big recirc style bypass valve?

Is the "rich" shift a negligible cost for surge? or is there something i'm missing?

I was thinking the recirc style bypass is optimal if you running the stock ecu in any form, ie. opensource, Cobb AP, Utec, aftermarket piggyback, etc..

Even with a fmic, it can be plumbed back into the hotside piping to keep the fmic pressurized, rather than into the turbo inlet (post maf) just to keep consistent with the originl stock subaru design flow.
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Old 01-30-2013, 11:37 AM   #2
207STi
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Most of the guys running big turbos ditch a maf based system all together and go with speed density. Vta is no problem with a SD setup.
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Old 01-30-2013, 11:41 AM   #3
07VTRex
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^ correct. size of the turbo is irrelevant it is the fact they are MAP tuning instead of MAF tuning
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Old 01-30-2013, 12:12 PM   #4
...CHUCKLES...
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I do it because it sounds bad ass. That and less routing.
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Old 01-30-2013, 12:17 PM   #5
rdieder
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^haha, VTA does sound badass.

thanks for the replys.
if i go with a Cobb SD tune with a VTA, will my around town mpg suffer? Im guessing that it still would use MAF around town and cruise situations until i trip over into open loop where SD takes over.
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Old 01-30-2013, 12:20 PM   #6
...CHUCKLES...
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If you have a compitant tuner and a nice tune then your MPG should not suffer.

What makes your MPG suffer the most is your right foot.
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Old 01-30-2013, 12:45 PM   #7
spintheground
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Am I the only one who dislikes the sound of VTA?
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Old 01-30-2013, 12:56 PM   #8
KillerBMotorsport
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Even without SD, a blow through MAF can be tuned for as well.
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Old 01-31-2013, 04:32 PM   #9
Steve.804
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Quote:
Originally Posted by 207STi View Post
Most of the guys running big turbos ditch a maf based system all together and go with speed density. Vta is no problem with a SD setup.
And it's usually the big turbo guys that do that in order to take advantage of the larger turbo inlet. 4" intake + MAF = no bueno.

I'm running a VTA BOV on my 35R set-up and I'm still using a MAF sensor but that is b/c it's what came with my kit and I was on a time crunch to get it tuned. I have a step-down coupler coming off the compressor housing down to 3".

I plan on doing my engine build soon and one of the things I'll be addressing is using a recirc. valve even though I will be going SD. The noise gets pretty damn annoying and when you have an EWG dumping to atmosphere...how much more noise do you need?
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