# Is a BOV really needed???



## nitr0us (Jul 7, 2003)

I have a question. On audi a6 2.7TT how come there arent any BOV's??? Is it because the engine is so finely tuned?? Is it because theres no excess air to be leaked out for some reason??

this has been puzzling me.

peace


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## niky (Jul 20, 2002)

erh, where did you see this info? post it up so we can see...

i've seen turbos without intercoolers, but never without the BOV!


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## sentragtr20 (Jun 8, 2002)

There is a bov there. It just cant be seen. If there was no bov or bypass valve, the turbo would go in a matter of weeks..


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## Murph (Aug 8, 2002)

stock setups usually run a small recirculating BOV. What this does it take the air from one side of the turbo back to the other side so unusual pressure doesent build up. Just because you dont hear it doesent mean its not there.

You could run it without but once the engine stops taking in air (release the gas and throttle plate closes) then where does the air go? It builds up and eventaully goes back through the turbo which is a BAD thing. Its very hard on the compressor wheel. Also if you released the throttle and then gave it some right after, you would be letting in a pretty large pressure of built up air and letting that into the engine would cause it to run lean for a moment. Also bad.

Of course it IS possible to not run one w/o problems, but you would have to be running a pretty huge turbo that would be running at very low speeds.

pls. unless you have something NEW to add or a Q pls dont just say what i said again


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## nitr0us (Jul 7, 2003)

thanks guys. and no if i wanna say exactly what you said again to someone else i would definitely give you sone credit.


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## James (Apr 29, 2002)

some systems use ball bearing turbos and run light boost, no BOV, and last a long time... IE the JWT SR20 Kit they sell has no BOV...


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## Paul79UF (Jan 23, 2003)

why would you not want a BOV....they sound so sweet.

ever seen the stockholm vids where that turbo car out runs the cops...

my car's supercharger whine is nice but every so often I wish I had a turbo with a nice loud BOV


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## chimmike (Oct 17, 2002)

Paul79UF said:


> *why would you not want a BOV....they sound so sweet.
> 
> ever seen the stockholm vids where that turbo car out runs the cops...
> 
> my car's supercharger whine is nice but every so often I wish I had a turbo with a nice loud BOV *



if you have a MAF with turbo you need to recirc the bov, which reduces the sound quite a bit.....................................but you didn't know that cuz you don't own a sentra


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## boost_boy (May 25, 2002)

CA18DET engines didn't come with a blow off valve and I don't think nissan made a mistake when they designed it. Some cars have and some cars don't. 5-7psi of boost and no BOV equates into a turbo that's going to live a long time and wastegate flutter sounds pretty cool as well !


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## Crazy-Mart (Jul 14, 2002)

E15ET didnt had any too.... the Ca18ET didnt as well.... seam like nissan found that a BOV was useless with those low boost engine...


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## ForsakenRX7 (Mar 14, 2003)

Any turbo car I've ever worked on has had one. Personally, if I had a car that didnt come with one I'd sure as hell install one. They do have a use besides a "cool sound".


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## sentraspeed (Mar 26, 2003)

if you look alot of drag race civics and stuff that run like 30 or 40 pound of boost dont use blow off valves...they just let off the throttle slowly and let the boost build down because they have yet to find a bov that can hold tht much boost for one and it is just not nessicary


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## nitr0us (Jul 7, 2003)

haha

ic


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## ForsakenRX7 (Mar 14, 2003)

Well, you guys can run all day long without a BOV. Not me. Cause I know what the whipple sound means between shifts without one.


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## Engloid (Jul 7, 2002)

Have heard of the z31 J but NONE of them had a bov on them….and I’ve known the turbos to last as much as 200k miles. If you’ve read Maximum Boost, the t3 on the z31 was mentioned as the perfect turbo for the car…but he didn’t say it needed a bov.

Do you need a bov? No. 
Are they good to have? Yes.
Can they make a turbo last longer? Theoretically, yes. Have I personally tested, no.
Can they reduce lag? Yes?


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## javierb14 (Jul 9, 2002)

edit:
nevermind


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## UnderDog (Jul 14, 2002)

Those don't work.


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## UnderDog (Jul 14, 2002)

Download them and post them somewhere else. I can imagine what they did... that sounds like a really cool idea. Mount a duck call to a BOV...

SHIFT_quack


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## SentraStyles (Dec 31, 2002)

So their is no way to get away with not recirculating the BOV?


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## chimmike (Oct 17, 2002)

SentraStyles said:


> *So their is no way to get away with not recirculating the BOV? *


if you don't want the car to idle.


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## boost_boy (May 25, 2002)

When I used to use JWT stuff in my car, I did not recirculate my blitz BOV and it would cut off every now and then, but it idled perfectly. Get a VPC or go standalone and you can blowoff all you want without sacrificing driveability!


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## Engloid (Jul 7, 2002)

chimmike said:


> *if you don't want the car to idle. *


I've got to speak out...for all the guys like me that have proven this wrong.

Fact is that I ran 12psi and nitrous with an atmospheric venting bov. 

Check out z31.com.... most guys there use the same thing.

And the problems some do have with these are due to it running so rich between shifts that it bogs down in the next gear. At idle, a bov should ALWAYS be closed.


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## javierb14 (Jul 9, 2002)

ya...it will idle depending on what bov u have. i ran a 1st gen DSM of teh old GA16DET and it would open a little @ idle. i didnt want to crush it, so i had no way of adjusting it. with it recircd'd, driveability was just like stock 

GA16DET idling phat(rich) with bov to atmosphere 

GA16DET idling like stock with bov recircd'd


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## xxskaboomx (Jun 14, 2003)

Javier, 

The links dont' work


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## Engloid (Jul 7, 2002)

They work fine for me. You must have some problem with your media player or something.


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## boost_boy (May 25, 2002)

> They work fine for me.


 They work for me as well!


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## xxskaboomx (Jun 14, 2003)

Oops...my bad!


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## greg5286 (May 7, 2003)

what if you get the intercooler kit from jgy customs for the sr20det with the maf on the air filter going from the turbo to higher up in the engine bay...
http://www.jgycustoms.com/se-r_intercooler.htm
that way you have your maf on the turbo filter like a regular intake and you can have an atmospheric venting bov


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## Engloid (Jul 7, 2002)

Really I think the issue is in the ecu. Some cars will go way too rich between shifts and others it's not so noticable.


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