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Old 10-31-2006, 12:00 AM   #1
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Default Why BOV at Throttle Body?

I have read that it's best to connect the BOV into the charge pipe nearest to the Throttle body, but not sure why?

My plan is to mount the BOV valve close to the turbo compressor outlet (FM2 style) with a short shot into the intake and the vacuum Line tapped into Brake Vacuum Assist behind the Master Cylinder. It just seems cleaner this way with no long tube or hose running across the engine bay from the TB.
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Old 10-31-2006, 12:09 AM   #2
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doesn't matter much either way
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Old 10-31-2006, 12:17 AM   #3
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I have researched this thoroughly.
There are three schools of thought.
#1: It must be between the IC and TB, no other way will work.
#2: It's OK to put it between the Turbo and IC, #1 guys are dumb.
#3: It doesn't matter.

The purpose of the BOV is to prevent backpressure waves off the closed throttle-body back into the compressor (I think). BOV placement on stock vehicles have engineered the thing everywhere.
I'm a #3 kinda guy because it's so much easier to route the recirc line 6" inches up into the intake rather than 3' across the front of the engine.

I don't think you'll find anyone who will say one way is distinctly better than another and have any proof why. If you do find that guy, I'll find you another who will say why he's wrong and tell you why another way is better also with no proof.

Maybe Corky knows.

I say put it where it's easiest for you to engineer it and drive the **** out of it.
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Old 10-31-2006, 12:23 AM   #4
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BEGI places it on the TB side.
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Old 10-31-2006, 12:30 AM   #5
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When you close the throttle, the bov opens and replaces the throttle as the lowest pressure area in the intercooler pipes. All the pressurized air in the pipes will flow towards it.

Putting the BOV next to the throttle body ensures the air keeps moving in the right direction. No reversing in the pipes. The turbo will actually keep spinning and pushing boost briefly, pretty much for the duration of the PSCHHHT sound. If the BOV is on the opposite side of the intercooler, the turbo has to keep most of the IC pipes pressurized during that time. If you can shift and open the throttle before the turbo loses momentum, you will basically not lose boost for more than a fraction of a second.

If you put the BOV near the turbo, all the air in the pipes will reverse and try to flow back towards the bov. While the turbo is losing momentum, it wont keep the IC pipes pressurized at all. When the turbo starts trying to push boost again, it will have to get all that air moving, which will slightly delay recovery of full boost.
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Old 10-31-2006, 12:41 AM   #6
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I think where ever the blow off valve is most hidden. They look like such eyesore and really detract from a clean bay. I like to sitck mine on intercooler end tanks.
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Old 10-31-2006, 12:45 AM   #7
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Quote:
Originally Posted by beerslurpy View Post
When you close the throttle, the bov opens and replaces the throttle as the lowest pressure area in the intercooler pipes. All the pressurized air in the pipes will flow towards it.

Putting the BOV next to the throttle body ensures the air keeps moving in the right direction. No reversing in the pipes. The turbo will actually keep spinning and pushing boost briefly, pretty much for the duration of the PSCHHHT sound. If the BOV is on the opposite side of the intercooler, the turbo has to keep most of the IC pipes pressurized during that time. If you can shift and open the throttle before the turbo loses momentum, you will basically not lose boost for more than a fraction of a second.

If you put the BOV near the turbo, all the air in the pipes will reverse and try to flow back towards the bov. While the turbo is losing momentum, it wont keep the IC pipes pressurized at all. When the turbo starts trying to push boost again, it will have to get all that air moving, which will slightly delay recovery of full boost.
Ya, what he said.
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Old 10-31-2006, 01:04 AM   #8
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Quote:
Originally Posted by beerslurpy View Post
When you close the throttle, the bov opens and replaces the throttle as the lowest pressure area in the intercooler pipes. All the pressurized air in the pipes will flow towards it.

Putting the BOV next to the throttle body ensures the air keeps moving in the right direction. No reversing in the pipes. The turbo will actually keep spinning and pushing boost briefly, pretty much for the duration of the PSCHHHT sound. If the BOV is on the opposite side of the intercooler, the turbo has to keep most of the IC pipes pressurized during that time. If you can shift and open the throttle before the turbo loses momentum, you will basically not lose boost for more than a fraction of a second.

If you put the BOV near the turbo, all the air in the pipes will reverse and try to flow back towards the bov. While the turbo is losing momentum, it wont keep the IC pipes pressurized at all. When the turbo starts trying to push boost again, it will have to get all that air moving, which will slightly delay recovery of full boost.

I think it doesn't matter where it is.

6 and 2 x 3....

WHITE90NA
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Old 10-31-2006, 01:13 AM   #9
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Beerslurpy's explanation makes sense. Thanks for the quick replies.

I think I will mount mine on the compressor side for appearance reasons. I also ended up with a big hole there welding the pipes together, it might be easier for me to drill out for the BOV than fill the hole.
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Old 10-31-2006, 01:47 AM   #10
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I would to TB too, beerslurby said it good enough.
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Old 10-31-2006, 01:51 AM   #11
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a couple supra guys i talked to about it said that there pre ic air temps melted his diaframe in the bov and he has been thru 3 or so int he last couple years. dont know if its just a small turbo problem or what but heat may be an issue.. then alot of people say the heat that is made cant get near what melts rubber... so thats a good point to .... haha

<---#3 guy
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Old 10-31-2006, 03:09 AM   #12
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it really doesn't matter either way. I've had it in both locations on a couple different turbo cars and really it made no difference at all in either place. In fact if someone went out to your car and moved it to the other side you'd never even know until you opened the hood the next time.
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Old 10-31-2006, 06:04 AM   #13
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It does promote faster throttle response, but doesn't matter all that much, it will work in either location pretty damn well.

Mark
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Old 10-31-2006, 10:09 AM   #14
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I'm also a #3 guy, although 2 out of 3 of my cars have the bypass valve cast into the compressor housing of the turbo.
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Old 10-31-2006, 11:57 AM   #15
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I had mine on the hot side and the next iteration of IC will have it on the TB side. I doubt I'll notice a difference. but it's nice to know the air charge wont be doing a U-turn.
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Old 10-31-2006, 12:03 PM   #16
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Quote:
Originally Posted by retro View Post
I have read that it's best to connect the BOV into the charge pipe nearest to the Throttle body, but not sure why?

My plan is to mount the BOV valve close to the turbo compressor outlet (FM2 style) with a short shot into the intake and the vacuum Line tapped into Brake Vacuum Assist behind the Master Cylinder. It just seems cleaner this way with no long tube or hose running across the engine bay from the TB.

Do it however you want...GOD

:gay:
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Old 09-05-2008, 06:54 PM   #17
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I run the BOV before the intercooler to prevent the hot charge from flowing through the IC. Prevents heatsoaking the IC.

But for fun Ill run both sides and pull data on boost recovery time.
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Old 09-05-2008, 06:57 PM   #18
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Hey NOOB!
Searching is good, even recommended.
But be sure to check the dates before you hit reply.
This thread is 2yrs old... and you just resurrected it to say absolutely nothing.

... and putting the BOV before the IC will have absolutely ZERO effect on heat-soak. If you'll read the thread again, there's no conclusive evidence for the pre/post IC placement... Corky even says this. Place it somewhere in the charge system that's most convenient... end of story.
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Old 09-05-2008, 07:09 PM   #19
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Hey guess what?


The turbo that I have from a mercadies 300D has the BOV molded into the compressor houseing!

and it works great!


I really think it doesent matter....
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Old 09-05-2008, 07:16 PM   #20
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Quote:
Originally Posted by samnavy View Post
Hey NOOB!
Searching is good, even recommended.
But be sure to check the dates before you hit reply.
This thread is 2yrs old... and you just resurrected it to say absolutely nothing.

... and putting the BOV before the IC will have absolutely ZERO effect on heat-soak. If you'll read the thread again, there's no conclusive evidence for the pre/post IC placement... Corky even says this. Place it somewhere in the charge system that's most convenient... end of story.
That’s exactly why Ill pull some data..... since no one has posted any conclusive evidence ( as you so graciously mentioned )

Heatsoak… disagree. The IC has a max thermal capacity before it gain heat…. Why make it work harder than it needs to?

Newb ... on this site maybee...
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