question about bov placement

[Sorath]

redoing my setup. whats pros and cons to mounting it on hot side or on cold side, any input is greatly appreciated.

thanks

[Supa Dexta]

Theres no solid evidence one way or the other that I've seen. Space issues would be the main concern.. A lot of the honda crowd have in on the hotside though... :dunno:

[EK 2.0]

Usually for best effectiveness, you want it mounted as close to the throttle body as possible. But having said that you dont want it so close that it disrupts air flow, and sometimes space is a huge constraint.

[gpomp]

before the intercooler :thumbsup: why vent all that air that you just cooled?

[n1zm0]

i say throw out hot, i think piston pounder aircraft, cold side is standard, but that may have to do with different altitudes / UMP etc :dunno:

[962 kid]

What does it matter what temperature the air your venting is (unless you have a dinky ass IC that you're worried about heatsoaking)? It's not going into the engine either way. Closest to the TB is the most efficient spot and the best for throttle response.

[zieg]

The idea is to prevent the pressure from spinning the turbo backwards, right? So where do you think it should be? I think it makes the most sense to have it close to the turbo. This also helps to prevent heating up the intercooler, but really the effect is balls compared to the amount of air already in there..

[962 kid]

If the idea is to prevent compressor surge, you'd want to put the BOV closest to the TB because the pressure builds up against the throttle plate.

[gpomp]

the pressure is the same at either end of the pipe, it doesn't "build up" at the TB.

[zieg]

Originally posted by gpomp
the pressure is the same at either end of the pipe, it doesn't "build up" at the TB.

:werd: physics dont work like that. Plus, who cares what the pressure is at the throttle, when you're talking about compressor surge? :nut:

[gpomp]

it's actually fluid dynamics :guns:

[962 kid]

:( Fluid dynamics was the biggest thing I regret not learning in uni. I know it doesn't "build up" at the tb, but would the pressure be equal at both ends even though it's not a closed system? Also, wouldn't the pressurized air start surging at the throttle plate, even if it was under constant pressure?

[zieg]

uhhh.. fluid dynamics, yes.. does that not fall under the more broad category called physics? as in the laws of physics.....?

[ryanallan]

Coming from browsing DSM forums for the past 6 years, closest to the TB seems to be the preferred location .

And as for pressure not building up at the TB, just think about the system in regular operation. Air is flowing through the TB and into the manifold. Now all of a sudden the TB closes. All the fast moving air has no ware to go and slams into the closed TB. Instead of all this air building up, and bouncing back into the turbo, by having the BOV right there you are able to get rid of it right away.

This topic seems to have no defined answer though. Manufactures use different location for their BOV.
Because I love to whore pics, here are some

Mitsubishi EVO : before TB
http://images.turbomagazine.com/features/0706_turp_006z+2003_mitsubishi_evo_8+engine.jpg

DSM : before TB
http://home.neo.rr.com/mast/pics/motor%20pic.jpg

Subaru : on intercooler
http://www.stockwire.com/images/comprofiler/plug_profilegallery/29074/pg_216911163.jpg

STI w/ front mount : before TB
http://images.importtuner.com/images/0605_impp_02z+2004_subaru_wrx_sti+engine_bay.jpg

VW/audi 1.8T : before intercooler
http://www.drwombat.com/audi/resource/18t.jpg

APS twin turbo for 350Z: before TB
http://www.airpowersystems.com/350z/front1.jpg

Nissan Silvia: before TB
http://www.designercars.net/biler/Nissan-Silvia-4.jpg
http://performancepartszone.com/wp-content/uploads/2006/10/nissan1.jpg

Titan Motorsports Supra : before TB
http://lib.store.yahoo.net/lib/titanmotorsports/titanengine1024x768.gif

RX-7 TT w/ front mount : before TB
http://carsinthefastlane.com/wp-content/uploads/2007/06/1993-mazda-rx-7-engine.jpg

[gpomp]

^out of all the pics you posted, only the sti and 1.8T show the stock mounting locations, and they are both before the intercooler.

[gpomp]

Originally posted by ryanallan
And as for pressure not building up at the TB, just think about the system in regular operation. Air is flowing through the TB and into the manifold. Now all of a sudden the TB closes. All the fast moving air has no ware to go and slams into the closed TB. Instead of all this air building up, and bouncing back into the turbo, by having the BOV right there you are able to get rid of it right away.
the air doesn't "bounce back" towards the turbo. it's a compressed fluid so if the bov is before the intercooler the air right THERE gets vented. the air doesn't travel backwards from the TB.

[ryanallan]

Originally posted by gpomp
^out of all the pics you posted, only the sti and 1.8T show the stock mounting locations, and they are both before the intercooler. the EVO and DSM are also in the stock locations. And the STI looks to have its BOV closest to the intake manifold, after the intercooler.

the other pics, even though not of OEM designs, show the logic of after market systems. whether the placement is for cost, performance, or aesthetic reasons, it is just interesting to note that all the after market systems above have their BOV before the TB.

[Mibz]

Originally posted by gpomp
the air doesn't "bounce back" towards the turbo. it's a compressed fluid so if the bov is before the intercooler the air right THERE gets vented. the air doesn't travel backwards from the TB. Won't having the BOV before the IC (or anywhere away from the TB) cause the air between the BOV and TB to reverse direction during vent? If the pressure is equal across the entire pipe and the BOV creates a low pressure zone then all air in the pipe is going to move there, meaning you're reversing air flow and making it harder to respool. That said, you're also double-cooling a section of air that doesn't get vented.

Either way, regardless of which position is best according to science I don't think it makes enough of a difference to really matter. Put it where you've got the space.

[hellraiser456]

in my opinion it doesn't really matter where you out it as long as it is big enough to vent the air (pressure) fast enough. you will notice different systems simply because some are recirculated and some aren't and it is sometimes easier to put the bypass valve somewhere else. as well like mentioned...space can be an issues as well.

i believe people say to put it beside the TB because when the bypass valve is open (when in vacuum) you are pulling air through that rather than through the turbo(which would be more of a restriction)...which would mean better throttle response at part throttle conditions.

however the key purpose to a bov/bypass valve is to ensure that you do not get compressor surge...and that shouldn't happen if your bov is working properly and it is big enough to vent the air, despite its location.

[962 kid]

Originally posted by gpomp
the air doesn't "bounce back" towards the turbo. it's a compressed fluid so if the bov is before the intercooler the air right THERE gets vented. the air doesn't travel backwards from the TB.

The air is a compressed fluid but it's not in a static system. It is moving, and it does surge backwards when it hits the throttle plate.

[stevo 27]

just before the throttle body is the best place simple

what happens when you close the throttle plate your turbo is still doing it's job compressing air forcing it to it's end desination .....the throttle body so having the bov right before the TB is just a more fluid movement

everybodys talking about physics im no genius but high pressure systems will always move out into a low pressure system correct????

soo if the air is moving out of the turbo through the intercooler then to the throttle body why would you put the bov before the intercooler so the air that is already pressurized in and after the intercooler has to reverse it's direction to be vented ??

and think is the bov is right before the TB theres no were else for the air to go but out right

we all know the air is moving at a high velocity so having the bov on the hotside = you let off the TB closes,bov opens, the already pressurized air after the bov reverses direction , (if your bov isnt massive) not alll of the fast moving air is vented ,collides with the the other pressurized system trying to escape and boom compresser surge

:dunno:

[DeleriousZ]

as said before, probably after the intercooler, before the throttle body.

think of it this way... you're still pushing air through the cooler when the bov is venting, and as soon as the bov closes, there will be a rush of air from the turbo (assuming full throttle shifting)

now do you want that air to have to go through the intercooler before going into the engine, or would you rather have a head of cooled/cooling air coming from the intercooler to the tb?

i'm guessing, depending on IC design, that you'll have a higher pressure (more likely mass of air) before/in the intercooler when the bov is venting because of the pressure drop and restriction in the intercooler.

that probably didn't make any sense at all... but it's late and during finals... :P