asianspeed

I'm doing a custom turbo project and I'm planning on using the aem cai pipe, will placing the bov before the pipe be a problem? I hear you should have it as close to the TB as possible, but I'm thinking that as long as it's between the TB and the IC it should be ok, right?

mos

It should be ok, but as I understand it, one of the purposes of having a BOV is to protect the throttle body from damage. It may not do as good a job if you place it furthur away. It will still serve its duty in protecting the impeller from damage via a "reversion" pressure wave from the closed throttle plate tho. I think thats its other purpose.

Elite Hatch

You are correct

TheIntegraGuy

I have mines between the compressor and the FMIC. It's in the fender shooting outwards. Then again, its different for me cause I don't have a honda anymore.

MiraiZ

a lot of peeps here put it right after the IC

RGAZ

Make sure the BOV is in a smooth path in the direction of the airflow and close to TB.

Consult Maximum Boost by Corky Bell for more info.

Randy

Charlie Moua

iTrader: (3)

\

other way around..... BOV is made to help protect backpressure in between shifts as your TB open and the suddenly close. When you shift there will be some pressuer that will bounce back to the turbo and is harmful to the turbo/fins it self.
BOV will release/bleed out exccess pressure befor it reaches the turbo.

FredoSP

a.k.a. Compressor Surcharge

Dublocivic

Yup... no BOV or inadequate BOV is hell on the compressor.. it wears out bearings quick causing shaft play and fin-2-housing contact. The air going back from the throttle plate to the compressor "surges" and pushes back into the compressor housing.

asianspeed

So basically, as long as it's before the compressor, it should do it's job of releasing the back pressure, right? And of course you'd want it before the intercooler as well because why have air pass through twice.

This is a little off topic but, let's say this was the piping and you placed the bov there.
+ = air
* = pressured air
-----------------------------
IC++++BOV****(10psi)**TB
-----------------------------
Then when the trottle body closes, there would be, I'm using 10psi, pressure returning back through the piping. Now if you place the bov further away from the TB, then that space will still have 10 psi of pressure. Then when you want to re-open the TB, wouldn't it take less time to build up boost again? Because you've made the area smaller to build boost by keeping as much air between the IC and the TB.

As compared to this:

-----------------------------
IC+++++++BOV*(10psi)*TB
-----------------------------
With this, you'd need to fill more space with air, and that would take longer, right?

Can someone help me figure out all of this turbo theory? If you haven't noticed, I'm very new to this. So any help is appreciated. Thanks


[Modified by asianspeed, 10:09 AM 10/15/2002]

Elite Hatch

Youre getting a little to far into it. It really doesnt matter that much about placement of BOV, especially if you are only running 10lbs of boost.

mos

I think you have it backwards. Re-read my post, you just restated what I already said, except worse. And I guess you have one of the new indestructable honda throttle bodies... nice

Dublocivic

There is 10 psi throughout the piping from the compressor to the throttle. When the throttle closes the turbo is still pushing air (for a sec) but has no where to go but back toward the compressor where it surges.
like this:
---------------
+ = positive pressure(10psi)
BOV= blow off valve
IC=Intercooler
C=Compressor
>>=air going into intake mani
<<=surge
T=Throttle plate
VV=exiting charge air
---------------
Now(boosting)

C>>++>>IC>>++>>BOV>> ++>>T(open)

Let off the throttle and T-plate closes
C>>++>>IC>>++>>BOV<< ++<<T(closed)
(Surge hits bov and exits) VV

This is why you hook up a vac line from the BOV to the manifold or vac source so when the throttle closes that line sees vac and the bov opens to eliminate surge.
Hope this helps!



[Modified by Dublocivic, 3:32 PM 10/15/2002]

asianspeed

Thanks everyone...

sushibug

i actually understood his post more then yours. he actually mentioned the turbo. people get BOVs to protect from compressor surge, not to protect their throttle bodies. actually, most people get it for the sound.. but you know what i mean

GOLDBERG

would Teeing the vac line on compressor too wastegate(where boost controller goes) be a bad source for a BOV vac line?

fsp31

>>would Teeing the vac line on compressor too wastegate(where boost controller goes) be a bad source for a BOV vac line?<<

Yep. Real bad.

It's the wrong source altogether. You want your BOV tapped to the intake manifold itself. Here's why. The intake manifold goes FROM boost TO vacuum (very quickly). Having both boost and vacuum available from the same source is very important to the proper working of the BOV.

When the intake manifold is under boost, this means you've got your foot on the gas and you're trying to make power. Bad time to have the BOV suddenly start bleeding boost right? Bleeding boost = power loss. To help keep this from happening, the line from the intake mani is sending positive boost to the BOV to help hold it closed against the "good" boost pressure. Remember, the waste gate controls boost, not the BOV...

When the intake manifold is under vacuum, this means you (probably) don't have your foot on the gas and you want the BOV to vent extra pressure left in the charge piping to prevent a pressure spike. This is especially important when you are between shifts and the compressor may be spinning at full speed. Suddenly the throttle snaps shut and there is all this air being stacked in by the turbo with nowhere to go. It's a good idea to have the BOV pop open wide as quickly as possible. The "instant vacuum" coming from the intake manifold under these conditions helps the BOV react quickly to the situation, thus helping the BOV to open and relieve the "bad" boost pressure.

Where it gets interesting is in deciding which BOV works best for your setup. Some BOV's completely bite. They bleed boost all the time. 2G DSM's come to mind... Other BOV's are designed to maintain some pressure in the charge piping to help reduce turbo lag. There are a lot of good ones to choose from. Good luck.

BTW, mount the damn thing about a foot down from the throttle body and be done with it!

GOLDBERG

would there be anything wrong with mounting bov by the compressor??between compressor and fmic??ityd be the easiest thing for me too do givin my situation..just would have a long vac line

Stu

Some where on this site is a setup where the BOV is actually right in the middle of the IC, and aren't WRXs like that too?

mskibbz-T

Hmmm... I have my BOV mounted on the top of the IC endtank, on the throttle body side of it. Any pros and cons to this setup? I've heard people say 6-8" from the TB and others say it basically doesn't matter as long as it is after the turbo and before the TB, I cannot even hear mine so I wonder about its functionality in its current location... I'll go turn off the 2 step and verify its working tonight

GraphiteAccord

as close to the compressor as you can get it will be most beneficial..

fsp31

>>as close to the compressor as you can get it will be most beneficial..<<

I don't agree. BOV's need positive AND negative vacuum in order to function correctly. Rigged up to the charge pipe or compressor housing, the BOV will still work (maybe, but not well...), but that's just because the compressor surge will usually produce enough pressure to force the BOV open. And the only place you'll get negative vacuum is at the intake manifold.

GOLDBERG

huh??isnt the vac part provided by the line that connects to intake manifold...

GraphiteAccord

Talk to FFgeoff about this matter, he has a very convincing arguement.

fsp31

>>huh??isnt the vac part provided by the line that connects to intake manifold...<<

Ok, I think there is some confusion here. My posts in this thread refer strictly to the placement of the vacuum source leading to the BOV, not the BOV itself. I don't think BOV placement makes much difference at low boost, but placement of the vacuum line most certainly does.

and the source of vacuum generated inside the line is.... dingdingding! the intake manifold.

this is getting massively redundant. Y'all just do whatcha "feel". Maybe it'll work or maybe you'll screw your turbo. https://honda-tech.com/zerosearch is your friend.