TTAWD

I'v seen a ton of GN's with out a BOV, I don't recall seeing any american turbo cars with one from the factory. I like hearing the turbo shutter.
Are they realy necessery if you have good clamps on all the connections.

ZL1Killa

iTrader: (17)

Diverter valve...................blow off valve ..............look em up

Johawk

iTrader: (2)

most guys have to return the BOV discharge back into the intake because if that air is allowed to escape the intake after its been metered by the MAF sensor it will make the car load up with fuel and even flood it out in extreme situations. DSMers use GM MAFs before the TB so they can blow of to atmosphere and for better flow but this takes some tunning

mahhddgtp

Sound is the main reason. The only time I think it would be necessary to plumb back before the turbo to 'help the turbo stay spooled in between shifts' is if you're running a gigantic turbo in comparison to your motor's displacement. If your friend's turbo is the stock turbo, Tell him he can plumb it how he likes... I just wouldn't plumb it after the MAF, for it would run rich*.

I agree with Speed's logic the most of all here... I don't think running lean would be an issue at all if the BOV dumps before the turbo.

mahhddgtp

I don't think I've noticed there being a lot of setups like this, though.. but it's certainly doable.

jRaskell

iTrader: (1)

Autos don't need BOVs as much as sticks. You don't get off the gas at all to shift gears, so it's WOT from light to trap. Stop and go situations are another story, but they won't provide any benefit to your quarter mile times in an auto.

Not having a BOV will cause all that pressurized air to exert additional pressure on the compressor of the turbo. This will induce lag in between shifts (exactly how much depends on how much boost you're running and what kind of turbo you're using), and that additional pressure on the compressor will increase wear and tear on the turbo. How much again depends on the circumstances. Again, these effects are more prevalent on a stick than an auto, but they aren't entirely absent from autos.

RW99

Ditto the above.

Mine is plumbed back to the intake, but I still get a nice flutter on (M6) shifts under boost. Combine that with an exhaust that keeps V8 rumble/roar and it's a cool combo... very fun to demonstrate to rice-boys in their Evos/STis.

As for performance, there's absolutely no problem with re-spool. Part of that may be due to my setup, though: stock cubes with a T67.

silver01z06

a few things people have said that are right.

1. autos dont need bov as much because they do not blow off on shifts. automatic transmissions keep the engine underload while shifting. the throttle body never closes to cause the back flow and compressor surge.

2. cars are different on how they meter air. some cars are speed density some use maffs. on 90-99 dsm the air was metered by the maff and if you vented to atmosphere it would run rich and could stalling issues. alot of dsm's used HKS VPC's that converted the car to speed density. by doing this they could vent atmosphere and avoid the problems.

3. venting atmosphere or back in is really preference. the sound is louder and alot of people like that. another issue no one has talked about and i know dsm's used to do this some was, oil. you end up with some oil in the intake manifold as rings loosen up and time. when you vent back into the intake you blow a little oil into the turbo housings. never heard of anyone having an issue with it. dont know if it is good or bad. but the turbo doesnt need it.

785T/A

iTrader: (5)

He should just clamp a turkey call on his bov. thats the best sounding one ive heard. There is a vid around somewhere....