# bov placement?



## SXSENIS (Jun 9, 2002)

I've noticed quite a few turbo kits with the maf sensor just in front of the turbo inlet. Now my ? is why not put the maf closer to stock location and place the bov before the maf instead of after.

The reason I ask is the recirculating bov that is said to be needed to avoid the engine stumbling at stops and in between shifts is placed after the maf meter. If you place it before the maf it will relieve boost spikes before the maf reads the incoming air and avoid this mishap, and it would allow you to run a reg. bov that vents to the atmosphere, right?

If you can't do that. where is a good place to locate it and where does it circulate to? I've searched everywhere on the web to find a diagram of the installation of a rbov and or a explanation on why it is set up this way. thanks


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## James (Apr 29, 2002)

you have to put the bov between the turb and the tb with it relieving air to after the maf (meaning between maf and compressor) because if you did it any other way you'd either run rich or run lean!


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## SXSENIS (Jun 9, 2002)

So you mean like it loops from the turbo to tb back into the turbo inlet were its recompressed and then sent back to the bov or tb{if under throttle}.

Would you place it before or after say a intercooler? Or does that not really matter being that its just going to be recomp. and reheated. I geuss the shortest easiest route would be best.

If you slip that extra{over boost} air behind the maf wouldn't that confus it[ to rich or to lean].
But if you relieve the over boost before it gets to the maf the maf wouldn't even known it was there and would meter only the air used and not have 20 to 40% extra.... Wait That shouldn't matter either. the bov would just relieve what wasn't being used for whatever boost level your running.

I think I got it. Had to draw a pic


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## wes (Apr 30, 2002)

*Clarification.*

BOV's are typically mounted between the outlet of the intercooler and the throttle body. When the TB is closed the boost pressure is vented out of the BOV, MAF cars need to have the vented air re-routed back into the intake stream AFTER the MAF. It goes in AFTER the MAF because it is air that has already been metered by the MAF. 

Hope this makes sense. Remember that the MAF get's moved in a turbo install. It is connected in the intake pipe leading to the intake of the turbo.


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## javierb14 (Jul 9, 2002)

the old setup in my old car.









i vented it to atmosphere a couple of times. when vented to atmosphere the car ran really rich. it ran 9.5-10.5 AF at idle and would fall on its face during shifts....if it didnt stall. 

we like to mount the blow off valve closest to the compressor outlet before the intercooler. one reason being that it vents hot air instead of air cooled by the IC. its relatively easy on a MAP car, but is a little more difficult on a recirculated MAF car.


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## Luis (Apr 30, 2002)

I usually try to place my BOV's as close to the throttle body as possible. Usually 4-5 inches away from it, depending on the piping. Your car will kinda stumble between shifts and/or run rich. I've actually had some success with the HKS super sequential BOV. It doesn't leak out any air at idle and only releases a minimal amount of air during shifts. On the last car I installed on the car didn't run rich or backfire during shifts or stumble. But your mileage may vary. If you want to do it "right" or perfectly by the book, you should recirculate.










Luis


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## dave_f (Dec 11, 2002)

Venting the BOV before the MAF would be double dipping (measuring air that has already been counted)... not to mention your MAF sensor wire wouldn't last very long if you were pumping hot oily boosted air through it. That's why you don't see MAFs mounted after the turbo and before the throttle body. If your car is MAF recalculate your BOV (it doesn't sound as cool but its the right way to do it). Your ECU doesn't like it if you vent metered air to the atmosphere. 
-dave


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## SXSENIS (Jun 9, 2002)

I dont want to vent into tha atmosphere. It does sound way cool but I dont want any drivablity problems.


So a recirclating bov would need to be routed back into the intake stream after the maf. Got it. the maf is moved to keep that nasty boosted air off of it{being why its placed on the turbo compressor inlet not the compressor outlet}. That being said what would you think of placing it after the intercooler and Recirclating it back into the compressor outlet pre intercooler to help increase the intercoolers effectivness? It would also be easier to route it this way because the two{pre and post}icp are rather close to one another.

javierb14 pics cleared up alot for me but has anyone tried what I have suggested or placing it so its feed back into the turbo compressor inlet aft the maf my only option.


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## dave_f (Dec 11, 2002)

the reason you want it as close to the throttle plate as possible is because at full boost and wide open throttle you have a stream of air being forced into the intake plenum, when you snap the throttle plate closed the air has no where to go but the blow off valve. Because the blow off valve exit is at a lower pressure (atmosphere or recalculated) the air id diverted through it. If the Blow off valve is place before the intercooler or closer to the turbo, the pressurized air that was about to go into the intake just before it shut would have to reverse direction, travel backwards down the intake plumbing towards the BOV... mot the most efficient use of a BOV. If you were to plumb the outlet of the BOV after the turbo, it wouldn't function properly either... because the BOV only work if there is a pressure differential across it... i.e.. boost on one side atmosphere or vacuum on the other (the air will always take the path of least resistance). if you have boost on both sides the air would wouldn't travel through the valve.
-dave


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## SXSENIS (Jun 9, 2002)

so the best place to install it would be {ideal} 3-12inches from the throttle body and go through the slitly more difficult plumbing to recirclate the over boost into the air inlet aft the maf. I see or understand what you mean about their being pressure differential
in the compressor to tb track{the pressure would not change in the icp if I routed it to before the ic it would stay at a constent not allowing the bov to work}

Does it help keep the turbo compressor spooled by routing the blow off valve into the compressor inlet aft the maf?


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## dave_f (Dec 11, 2002)

the main purpose of having a blow off valve installed is to prevent compressed air from backing up into the turbo when you close the throttle. the sudden surge of boost will put a lot of wear and tear on the turbo's bearings.
-dave


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## Blu200SX (Jul 22, 2002)

so it is a bad idea to have a BOV that is vented into the atmosphere? i think that is what you guys are pointing out here but is there a way you can install one and have good results?


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## AznVirus (May 8, 2002)

some companies make recirculating blowoff valves, such as GReddy. if you really want to get the sound then i suggest getting that, but its best that you recirculate it all back into the intake tract.


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## Murph (Aug 8, 2002)

there must be a way to vent to the atmosphere and still not run rich.

how do they do it?


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## dave_f (Dec 11, 2002)

you could put a miniature MAF on the exit of the BOV so the ECU knew how much air your letting out so it could back out the appropriate amount of injector pulse width. but seriously... you can get a blow off valve to open and shut really quickly so as not to let too much air out and minimize the over rich condition inherent with atmospheric venting of a MAF system. but doing this conflicts with actual purpose of having a BOV in the first place. There are people that venting BOVs on MAF cars and they swear that their cars run have been running fine for years and there aren't any ill effects, but when it comes down to it, venting to the atmosphere isn't ideal. There are various standalone engine management systems that allow you to convert your car to a MAP system... this will allow you to properly install a atmospheric BOV.
-dave


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## Murph (Aug 8, 2002)

thanks dave!


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## ForsakenRX7 (Mar 14, 2003)

The Apex'i AFC actually has an adjustment to lean the car out a lil more between shifts to adjust for the enrichment cause by the measured air being dumped to the atmosphere. If you have one installed you can just use that feature. But honestly on yalls car its a better idea to just route the BOV back to the intake. Unless of course your running a Hks vein pressure regulator. Cause then you dont have a MAF anyways.


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## James (Apr 29, 2002)

Man all this talk because ppl want to hear the 'phoooosh' sound... this is proof positive that boost is as addictive as crack cocaine...


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## ForsakenRX7 (Mar 14, 2003)

James said:


> *Man all this talk because ppl want to hear the 'phoooosh' sound... this is proof positive that boost is as addictive as crack cocaine... *


Yes, yes it is. I need more. Much more.


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## James (Apr 29, 2002)

Tell you what, you give me your first born son and I'll fix that right up for ya!


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## ForsakenRX7 (Mar 14, 2003)

Can I have the boost first?


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## James (Apr 29, 2002)

no, first one's free, first born son or no deal!


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## Blu200SX (Jul 22, 2002)

routing it back into the intake is just boring, plain and simple, i wanna find a way to make that nice high pitch whistle. Then everyone will be breakin their necks lookin where the sound came from cause they know turbo is right around the block.


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## 1fastser (Sep 30, 2002)

...and to recirculate it, I'm using a hose between the BOV and the intake to the turbo. The Cobra MAF will be at the end of the piping going to the turbo, the filter will be on the very end.

Jody


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## crud in your face (Apr 14, 2003)

ok well i can see i need to recirculate, but are there any valves out there that recirculate and still make the wonderous sound we all love? i know hks make a recirculating setup for their ssqv valve, does it put any sound out? how tough would it be to use an AFC and vent to the atmosphere, because thats what im planning on useing for management.


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## 1fastser (Sep 30, 2002)

You'll still hear it and it still sounds great.

Jody


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