Blow off Valve Question.

Sometimes I head Loud Blow off Valves and sometimes I hear quiet ones. What makes it loud or soft? Is it how much boost you are running or is it the kind of BOV that you have?

I think it depends on who makes it... but I'm sure a turbo making 10psi is going to be a bit louder than one making 5psi *shrugs*

Not really sure tho

-Grendel

Originally posted by Grendel
I think it depends on who makes it... but I'm sure a turbo making 10psi is going to be a bit louder than one making 5psi *shrugs*

Not really sure tho

-Grendel

Thank you. Is there anyone else that knows this question?

it depends on the piston design. some have smaller pistons than others, producing less noise. others just have smallish openings, resulting in a high pitched whistle. some have horns to amplify the sound. and a few have dual drive setups, two pistons with the ability to adapt for a wide range of boost without changing springs which will whistle at low boost but have a deep "whoosh" at high boost (HKS Super SQV BOV).

depends alot on the type u buy. the greddy type s sounds much different then the hks. the sound stays pretty much the same at different boost levels, its just loader under higher boost.

Originally posted by drift
it depends on the piston design. some have smaller pistons than others, producing less noise. others just have smallish openings, resulting in a high pitched whistle. some have horns to amplify the sound. and a few have dual drive setups, two pistons with the ability to adapt for a wide range of boost without changing springs which will whistle at low boost but have a deep "whoosh" at high boost (HKS Super SQV BOV).

If I have a Greddy Kit running 7PSI What BOV do you recommend to give the loud Whoosh?

Originally posted by Frostbyte


If I have a Greddy Kit running 7PSI What BOV do you recommend to give the loud Whoosh?


use the BOV that comes with it, the Greddy Type-S i believe.

if you want louder, get the original Blitz single drive BOV or the TurboXS type-h RFL.

Actually the Greddy Kit does not come with a BOV that is why it is Street Legal. If it had a BOV it would not be legal in California.

Also, the same blowoff valve will make a different sound on different cars even running the same boost. Dont' ask why, it just does. We put an HKS one on a civic, and an eclipse both running 6PSI and the blowoff sounded totally different.

BOV's have a baffle built in. If you take it out you can make them louder. I read that in a thread either on this board or on www.3si.org a while ago.

Will a BOV still work good w/ auto/turbo? Does the throttle being wide open at all times, does that affect the BOV? Thanks for the info

your throttle body will still close in between shifts... i have seen lots of auto eclipses running with bovs....they blow just like a stick

Originally posted by Frostbyte
Actually the Greddy Kit does not come with a BOV that is why it is Street Legal. If it had a BOV it would not be legal in California.
HMMMM I thought the GReddy kit was street legal due to the fact that it is CARB approved thus making it legal.The other Kits are not(except now for the new APEXI kit)

actually a BOV on an automatic car functions differently from that on a manual. The throttle stays open all the time on an automatic as long as you have the petal down. It will not blow off in between shifts but it doesnt need to. Also the turbo only has to spoon once in an automatic, unlike a manual, where it has to respool evertime you shift gears. The reason it blows off is because the car has gone from boost to vacuum (when you take the foot off the petal to shift gears). In an automatic it will only blow off when you take your foot off of the gas.

Originally posted by BoostinSOHC
actually a BOV on an automatic car functions differently from that on a manual. The throttle stays open all the time on an automatic as long as you have the petal down. It will not blow off in between shifts but it doesnt need to. Also the turbo only has to spoon once in an automatic, unlike a manual, where it has to respool evertime you shift gears. The reason it blows off is because the car has gone from boost to vacuum (when you take the foot off the petal to shift gears). In an automatic it will only blow off when you take your foot off of the gas.
Thats pretty close, but autos can also blow off. It depends on the gears. If you're reving at 7K rpms and have 12lbs of boost and tranny shifts, the RPMs will fall raising the boost and opening the BOV. It all depends

Originally posted by fjt

HMMMM I thought the GReddy kit was street legal due to the fact that it is CARB approved thus making it legal.The other Kits are not(except now for the new APEXI kit)

How do you think they made it CARB Approved? :rolleyes: