Where do you guys have your BOVs mounted and which works better?
I’ve got a lot of people telling me different things so I figured i would check here too.
The Ideal way to mount an Atmospheric Blow Off Valve is to
mount it before the MAF so when you blow off the engine
doesn’t lean out and or stall. If you have a Recirculation Blow
Off Valve then put it right after the MAF.
You know adam, i was thinking about that idea “mounting the BOV before the mafs” and I really can’t figure out a way for it to work. Because BOV must be placed after the Turbo and before the TB. MAFS will not really work if you place it between the turbo and the TB will it? The engine will run lean because the air is compressed in the intercooler… correct me if i’m wrong. The best way to do this is to run a map on a standalone, then you won’t need a mafs at all 
[The stock S13 BOV is mounted on the intercooler’s coldpipe.
When you guys say mounting before the MAF, does that mean right after the air filter?
If so, the blow off valve might not do anything since the air is not presurized yet (being right beside the filter and all)… and the blow off valve will never open.
Also, about relocating the MAFS, is that a good idea?
I think the factory MAFS are designed to meter atmospheric pressure air. If the air is presurized, and temperature changed, would it still work?
The MAFS basically senses the amount of voltage needed to keep the MAFS wire at a certain temperature. If the air is compressed and is hot, and mafs is mounted where the air is compressed, it might take 0 volts to maintain the temperature (sensing no air). However, there is a lot of air in there :)… wouldn’t it make it make the engine run lean all the time?
I could be terribly wrong though, so please tell me what you guys think.
Some cars have the MAF on the boost side or MAP’s. That’s what he was talking about I think.
If you mount it closer to the TB a bit better response. If you mount it closer to the turbo then you get longer turbo life.
I read a bunch about this and its argued my many that it doesn’t matter.
One of the arguments were this:
Take a straw and blow in to it wile covering the end. Then move your finger and the pressure is release. Now do it again but poke a whole in the side of it. Same about of pressure release at the same amount of time.
i just ended up putting it on the hot pipe for convenience to resercution. but if it was on the cold pipe air would be colder letting colder air in to the turbo when reserculating.
Mounting a bov on the hot pipe can cause you car to stall when coming to a stop, becuase it is dumping metered air. it’s all about adjusting the bov
so that it woun’t open at a surtain pressure. your car won;t lean out if it does have enough air!! it richen uo, hence more fuel to air ratio.
mount it on the hotpipe for turbo life, that’s what’s it for. and recir it if
you don;t want the sound and the problems that might come.
Adam was refering to going
filter/turbo/BOV/MAF/IC/TB
but i dont know how that would effect the MAF. Wouldnt it be in a pressurized state for a longer time? which in turn would effect its behaviour
Mines mounted on the hot pipe, because it was the only place it would fit, but i plan on moving my MAFS after it, or to recirculate the air. It seems generally people put the BOV on the hotpipe because where ever you go to buy an aftermarket hotpipe, you will find more with precut flanges on it than without.
I am planning on moving my MAFS and BOV to the cold pipe side so that
they are more effective. Just one of the many projects for this summer.
I’d like to know how much response is loss on a stock setup.
The main purpose of a BOV is to vent pressure out so it doesn’t slam back into the turbine.
If I had more access to tools, I’d rather a way to shorten the IC piping/reduce bends for response, and keep the BOV mounted closer to the turbine side.
^^^ thats my setup right now …, but apparently the life of a turbo is not affected that much by a BOV, its like 1 month or something small. also, as far as mounting the BOV on the cold pipe for better response but less response, i dont quite see, i think it is acctaully the opposite, heres why: we know that air is compressable, and when traveling at those speeds has a good deal of momentum, once the throttle plate shuts, the air that was just sent from the turbo will still continue toward the TB, compressing it and dispurising it out of the BOV which is mounted there, actually removing more air, which will need to be filed up/compressed later, if the BOV is mounted closer to the turbo, it will dispurse the air that just came out of the turbo, then the air will from the TB will come backwards towards the BOV. But if you shift really slowly anyways all of the air will be dispursed and this wouldn’t matter, … i hope somebody understands what i’m talking about.
so is cold pipe best?
i dont get what you are saying, sorry, my point was that the BOV closer to the TB it will expell more air faster than on closer to the turbo because that is the direction the air is travelling, and due to fast shifting, if the BOV is close to the TB there will be less air in the system, you have more space to fill up to start boosting, but if it is closer to the turbo, there will be more pressure in the pipes already so you will have more response. I hope you see my point.
actually think about it like this, you get lots of people and have them run down a hallway as fast as they can, all of a sudden you close the door at the end of the hall in the direction of travel, (btw in this hallway it is not singal file so people can pile up) it is easy to see that the most compression and force will be on the end that just closed even though the build up will eventually be affected at the end of origin. Also lets say 2 doors open at either end, more people will run throught the door at the end(where the other opened) due to the fact that there are more people there to exit.
so if we use this analogy to the fact that to have better response, after the BOV goes off IF we want more air in the system, then it shows how a BOV closer to the turbo (origin) will leave more air in the system.
…uh only example i could think of, lol.
IMHO - mount the BOV as close to the throttle body as possible and plumb the bleed off back over to the intake between the MAFS and the turbo. The reason for this is both throttle response and leaving the already metered air in the system (closed loop) - don’t vent the BOV to atmosphere.
that would be the most optimal and effectient way.