BOV Question

smh0101 · Post by **smh0101** » Tue Oct 09, 2007 4:19 am

For some reason I was under the impression that these cars didnt need a BOV but there are a whole bunch of threads regarding BOVs and ICs.

So my question is when I put in an TMIC will I need a BOV or what?

I did a search....

So what is the diff between a BOC and a Recirc Valve

555BCTurbo · Post by **555BCTurbo** » Tue Oct 09, 2007 4:23 am

BOV blows off air to atmosphere...

Bypass valve recirculates the air back into the intake pre-turbo

Bypass will make the car run better and isn't ricer...imho

dropdfocus · Post by **dropdfocus** » Tue Oct 09, 2007 4:40 am

Perrin and Go Fast Bits both have models that allow you to choose either atmospheric or recirculation for the stock WRX intercooler.

http://www.gofastbits.com/index.php?par ... wrx_hybrid

http://www.perrinperformance.com/produc ... ategory=37

smh0101 · Post by **smh0101** » Tue Oct 09, 2007 4:54 am

Yeah I dont like the river soundin psssssss after every shift...

So why do you need one... Sorry bout bein a n00b on the subject.

denver_whitest185 · Post by **denver_whitest185** » Tue Oct 09, 2007 4:59 am

you can recirculate a hks ssqv with the right connector....

http://i42.photobucket.com/albums/e344/ ... 0004-5.jpg

HKS is a better design imo, since its a pull type intsead of a push, it can't leak. the only other pull type i know of is a OEM MR2 turbo bypass valve.

its quiet when its recirculated too...

dropdfocus · Post by **dropdfocus** » Tue Oct 09, 2007 5:06 am

Well, to answer your question... As the turbo spools up, it creates pressure. Well, that's all good untill you let off the throttle to shift and the openning to the throttle body shuts. The turbo is still spinning at that point and the pipe leading to the throttle body is still under pressure with no where for it to go. This is where the BOV or BPV comes into play. You can vent this pressure to the atmosphere (engine bay) or you can recirculate it back to the intake tract as it leads into the turbo. The BPV allows the pressure to be sent to the turbo which keeps it spinning and you don't really run into the lag you would if you vent the pressure to the atmosphere (the turbo slows down & has to spin back up again).

denver_whitest185 · Post by **denver_whitest185** » Tue Oct 09, 2007 5:49 am

smh0101 wrote:For some reason I was under the impression that these cars didnt need a BOV but there are a whole bunch of threads regarding BOVs and ICs.

you don't nessisarily need one, but its a good idea. celica alltracs do not come with any sort of bypass or blowoff valve, but ive see stock turbos (steel shaft ct26, 9psi) last past 200k miles. when you don't release the pressure, it will go back into the turbo a bit, creating compressor surge. a bypass or bov will help with spool a little bit, and make your turbo last longer. also, when you start to get some volume to your intercooler set (especially large front mounts with pipes) you will need one or you will screw up your turbo...

dropdfocus · Post by **dropdfocus** » Tue Oct 09, 2007 2:12 pm

Correct, you don't NEED one, as the 1.8 turbo GL's didn't have one, but the turbo likes it a lot better if you do have one.

Post by **Legacy777** » Tue Oct 09, 2007 5:31 pm

We can debate wether you need one or not, but any turbomachinery expert will tell you that you need one.

I think the only reason you find vehicles without them is because of either extremely low boost applications, lazy/cheap auto designers, or some other mechanism to allow the pressurized air to bleed off as to not cause compressor surge.

smh0101 · Post by **smh0101** » Wed Oct 10, 2007 6:24 am

Okay sounds good....

Thanks guys... I cant do an intercooler until next summer ( dad wont let me until then assuming that I have no accidents or tickets). So it isnt a huge deal yet but definitly good to know.

Sounds to me like BPV is a better way to go... More sleeper and more efficient (sp?)...

smh0101 · Post by **smh0101** » Wed Oct 10, 2007 6:25 am

but I can do a 3" Turbo Back

denver_whitest185 · Post by **denver_whitest185** » Wed Oct 10, 2007 7:28 am

why, for noise? you won't need a full 3" till around 300whp, and a 2.5" will normally fit tighter and cleaner. on lower power applications, you won't see a difference between the two diameters.

And yes, a bpv is better since the air is metered, and it will run rich when it releases the metered air to the atmosphere. if you were going off speed density and a map sensor, than it wouldn't matter.

Legacy777 wrote:I think the only reason you find vehicles without them is because of either extremely low boost applications, lazy/cheap auto designers, or some other mechanism to allow the pressurized air to bleed off as to not cause compressor surge.

or no space to put one

but thats trivial

Dynamic Entry · Post by **Dynamic Entry** » Wed Oct 10, 2007 8:22 am

Hijack alert!

I have an 06 WRX IC in the mail and so I must ask.....

Since I don't want to go the BOV route, what are my options?

Only these mentioned? What about retaining the stock BPV?
VVVVVVVVVVVVVVVVVV
Perrin and Go Fast Bits both have models that allow you to choose either atmospheric or recirculation for the stock WRX intercooler.

http://www.gofastbits.com/index.php?par ... wrx_hybrid

http://www.perrinperformance.com/produc ... ategory=37

denver_whitest185 · Post by **denver_whitest185** » Wed Oct 10, 2007 8:42 am

make an adapter for the stock bypass valve outlet (a plate with two holes that match up to the intercooler and a 1" fitting over the outlet with a lip on the end), pipe that with rubber or silicone to a bypass or bov of your choice, and recirc it if its a bypass.

Im going to find a stock mr2 bypass to hook up to it since they are pretty cheap, dependable, and they won't leak (pull type)

smh0101 · Post by **smh0101** » Thu Oct 11, 2007 12:01 am

denver_whitest185 wrote:why, for noise? you won't need a full 3" till around 300whp, and a 2.5" will normally fit tighter and cleaner. on lower power applications, you won't see a difference between the two diameters.

And yes, a bpv is better since the air is metered, and it will run rich when it releases the metered air to the atmosphere. if you were going off speed density and a map sensor, than it wouldn't matter.

Legacy777 wrote:I think the only reason you find vehicles without them is because of either extremely low boost applications, lazy/cheap auto designers, or some other mechanism to allow the pressurized air to bleed off as to not cause compressor surge.
or no space to put one
but thats trivial

No not for noise... because at Northwest Service Subaru Group I can get a good deal on a turbo back that is the same as livestrong14's.

So I am gladly going to take that... Wouldnt you?

smh0101 · Post by **smh0101** » Thu Oct 11, 2007 12:04 am

And today I hit that damn 150K mi mark. Phooey!

555BCTurbo · Post by **555BCTurbo** » Thu Oct 11, 2007 12:07 am

smh0101 wrote:

No not for noise... because Dale at Northwest Service Subaru Group said he would sell me a full 3" Turbo back exhaust identical to livestrong14's if I build him a website.

So I am gladly going to accept that offer! Wouldnt you?

That's funny...because I built the 3" turboback on that car...so finding an identical one might be kinda hard lol

smh0101 · Post by **smh0101** » Thu Oct 11, 2007 12:22 am

Hmm that is interesting. Well regardless Dale said 3" Turbo back so i dunno..

By the way what parts did you use on that?

555BCTurbo · Post by **555BCTurbo** » Thu Oct 11, 2007 3:13 am

smh0101 wrote: By the way what parts did you use on that?

3" pipe, mandrel bends, some flanges, and a muffler

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