I've got an s4 TII with a hybrid turbo making about 12 lbs of boost with stock injectors, 3rd gen fuel pump and IC. I'm upgrading to 720 secondaries, SAFC and FMIC. Is a BOV necessary or can I get away without it?

 

lol ummm i think you need it man the extra boost that your turbo produces is let out threw the BOV correct me if im wrong.
TwEaK

 

Yeah i would say so, because there is much more compressor surge now considering youve upgraded to a hybrid turbo and are boosting to 12psi. Keep in mind that the stock BOV is designed for stock boost levels and a stock turbo, both of which you have changed.

Just remember to get the right BOV and install it right cuz ive heard horror stories of aftermarket BOV's ruining engines when not installed properly.

 

as long as the stock one isnt leaking then you dont really NEED one. most people upgrade theres becuase they leak, and they want the sound. you probally could get away with stock one as long as yours doesnt leak.

 

also, i believe the stock is re-routed whereas aftermarkets tend to all be atmospheric. i want to say all cars with AFMs like the blow off valve to be re-routed into the intake. i'm not 100% sure, but its something to look into and consider how important it is.

 

You can have the aftermarket ones atmospherically vented, and in some cases rerouted. I know with my HKS SSQV you can get a kit for it to make it so it has a hose outlet on it to re-route the blowoff back into the intake stream.

 

yes you can get away without it.

in most places venting to the open atomosphere isnt compliant with emission standards.

simply put, when the throttle is closed all a BOV does is release pressure in the manifold so that it doesnt slow the spinning turbine blades.

 

You can get away with it but each time your boosting and letting off the gas your taking life off the turbo.

The BOV is inline to remove the pressure wave which travels through the intake once you shut the throttle plates.

Turbo spinning at 80k RPM doesn't like being forced the opposite way........

Open atmosphere BOV's are not legal on cars generally because you are releasing mapped air into the atmo so the air ratio is now changed.

I bought a Apexi FC zBov kit from Rx7stiore for like 125 or something. I got it because me Jspec didn't have it on there when shipped to me.

I would prefer a recirculatory BOV since I have a rebuild with a nice Vac leak so it already doesn't want to idle.

Temporarily I have tuned the BOV spring to stay shut so I don't release and mess up the idle.

I have stayed out of boost though.

 

The reason I was asking is because I know that there's a stock bov, but wasn't sure if the stock one could handle the higher boost pressures. Any tell-tale signs if it is leaking?