before the core, the air is at a higher pressure. We have ptu BOVs in both places and they work better and definately vent more air before the IC. You can actually feel/hear the difference.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FFgeoff &raquo;</TD></TR><TR><TD CLASS="quote">before the core, the air is at a higher pressure. We have ptu BOVs in both places and they work better and definately vent more air before the IC. You can actually feel/hear the difference.</TD></TR></TABLE>

Good I was hoping that my initial thought would work to be a good one. Thanks Geoff for that fact, it increased my confidence in the set-up
I was leaning towards the fact that venting at the higher pressure point in the system verses the lower pressure point would work more effectivly and possibly reduce flutter at low boost settings during engine break in period. I think I was heading in the right direction for once.

 

Plus, say youre running icewater through a WAIC. You put the BOV after the IC. This just "wastes" cold air, because its venting cold air into the atmosphere. Id rather waste Hot air. My BOV is going right on the 4 inch pipe that goes from my turbo to the IC.

 

You can put the blow off valve anywhere in the system that has pressure. air hitting the throttle plate is not the issue here.the issue is compressor surge. correct me if I am wrong but I have never seen a butterfly plate get bent from boost???????

 

i saw it on a nissan

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by intercooledJRSC &raquo;</TD></TR><TR><TD CLASS="quote">You can put the blow off valve anywhere in the system that has pressure. air hitting the throttle plate is not the issue here.the issue is compressor surge. correct me if I am wrong but I have never seen a butterfly plate get bent from boost???????</TD></TR></TABLE>

no the throttle plate is not the issue, but its the reason to even put a bov. when the throttle is closed, as in during shifting, the turbo is still making boost, and that charge has to go somewhere. without a bov, it will slam into the throttle plate and there will be a wave flowing backward towards the turbo, where it will try to spin the turbo backwards. corky bell's book simply states that the bov should be mounted as close to the tb as possible to catch this wave asap.

 

if i've been listening carefully to this thread....

then even if the BOV is mounted b4 the IC it wouldn't matter? Even if there is a wave flowing backwards wouldn't the wave be very suttle and not strong enough to "spin the turbo backwards" because alot of the air will have been vented through the BOV? I dunno .... i mean its like ..once throttle is closed where's the air going? backwards i assume...but since at the same time throttle is closed...the air that is supposed to go "backwards" is also vented out of the BOV? no? well... just a thought.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RGAZ &raquo;</TD></TR><TR><TD CLASS="quote">It should be as close as possible to the TB plate and should be a smooth transition from the charge piping to maximize smooth airflow.

This is covered for a few paragraphs in Corky Bell's book Maximum Boost.

Read it and learn.

Randy</TD></TR></TABLE>

I remember the book stating that you want a smooth transition, so you should be mindful of the angle that you mount the BOV. However I don't remember it stating that it should be as close to the TB as possible. I guess I have to go reread that section.

Anyways, I don't have a turbo setup yet, so I'm just theorizing here. Take it with a grain of salt. Since the purpose of the bov is to prevent compressor surge and protect the turbo and not to protect the throttle body, seems like it would be best suited near the turbo. Also, seems like having it near the turbo would also improve throttle response after shifting. Again, I'm just theorizing. Would be great to hear more from people who have had chances to test different setups.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kommon_sense &raquo;</TD></TR><TR><TD CLASS="quote">

I remember the book stating that you want a smooth transition, so you should be mindful of the angle that you mount the BOV. However I don't remember it stating that it should be as close to the TB as possible. I guess I have to go reread that section.
.......Since the purpose of the bov is to prevent compressor surge and protect the turbo and not to protect the throttle body, seems like it would be best suited near the turbo. Also, seems like having it near the turbo would also improve throttle response after shifting.......</TD></TR></TABLE>

I agree with these thoughts. In my case the BOV position is probably not the most "smooth" transistional location, but it was the best compromise of mounting locations available to me. I also agree with an earlier post in that I would rather vent warm compressed air than cooled compressed air.

But then again....is the difference that much to justify everyone to remove the TBody mounted BOV and place it near the turbo??.........probably not that much

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SLPR &raquo;</TD></TR><TR><TD CLASS="quote">
But then again....is the difference that much to justify everyone to remove the TBody mounted BOV and place it near the turbo??.........probably not that much</TD></TR></TABLE>

i agree...but some would want to venture and experiment with it... like i would

 

I have the same blow off valve on both my cars running the same boost. One is right after the turbo and one is right before the throttle body. The one near the turbo is a lot louder. I don't know if it works better but I like the extra noise.

 

I was all ready to mount my bov right after the turbo(before the i/c) cause i thought i would have room. well i was wrong. When i had my i/c endtanks done i didnt think about welding the bov flange on there but i wish i would have.
i had to mount it near the tb.
it wont hurt anything really but i was expecting to do it so that pissed me off.
maybe ill change it one day.

 

the way i see it is this.

what is a BOV? it's defense for your turbo against backwards surge.

when you play basketball, do you put your defense at half court? no, you put it just before your goal
right after the turbo is the best place to put it.

also, keep in mind, Corky's book was published in 1997. which means is was probably wriiten in 95-96. thats a LONG time ago. things change. new parts availbility changes, and so does placement of things. Just keep that in mind

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pissedoffsol &raquo;</TD></TR><TR><TD CLASS="quote">
also, keep in mind, Corky's book was published in 1997. which means is was probably wriiten in 95-96. thats a LONG time ago. things change. new parts availbility changes, and so does placement of things. Just keep that in mind</TD></TR></TABLE>

This is a good point, good ideas can be refined to better ideas. It is called continuous improvement.

 

This is a good thread.

I don't think turbo parts and the physics of airflow has changed much in the last 6 years. I agree the book is getting dated, but the physics parts are still accurate.

Some points:

If you mount the BOV near the turbo OF COURSE it will be louder. It has more air pressure there since there is no drop across the piping and IC to slow the air. But does louder = more effective. No. All it means is it is releasing higher pressure air.

Also, the BOV response time is dictated by how fast it detects vacuum and begins to open. By having as close as possible to the TB you are effectively shortening the vacuum line that "trips" the BOV. Putting it WAAAAYYY up front of the engine means a really long vacuum line and therefore a slower vacuum response. I admit, it can be a small amount of time, but we are looking for the fastest response possible, not big whooshy sound.

Again, the BOV is not only there to release pressure. It is also there to maintain air velocity in the proper direction. Having it close to the TB means the released air is still going in the right direction. And yes, air does have momentum. having it by the turbo means the air at the TB has to stop and bounce back, then when the BOV closes, it has to turn around again. Not what I would call an efficient design. Sure, the BOV at the turbo does prevent surge, but it causes havoc in the air tract after the turbo.

Venting cold air vs. warm air? Who cares, you have to release pressure no matter what which is a loss of energy (PV=nRT). The thermal air loss is very minimal and I would expect the air velocity issue would far outweigh the air temp loss issue.

Now that you have read all this and think the TB is the right answer, I am going to tell you in the real world IT DOES NOT MATTER. There is no real world performance advantage to either location. A perfectly equal empirical test will be nearly impossible to do fairly, so just put the BOV where you want to and be done with it. All the pros/cons listed would not gain you anything noticable in performance.

So have a good time and install it where you like it.

Randy


Modified by RGAZ at 9:52 AM 6/6/2003

 

good post!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RGAZ &raquo;</TD></TR><TR><TD CLASS="quote">This is a good thread.

I don't think turbo parts and the physics of airflow has changed much in the last 6 years. I agree the book is getting dated, but the physics parts are still accurate.

Some points:

If you mount the BOV near the turbo OF COURSE it will be louder. It has more air pressure there since there is no drop across the piping and IC to slow the air. But does louder = more effective. No. All it means is it is releasing higher pressure air.

Also, the BOV response time is dictated by how fast it detects vacuum and begins to open. By having as close as possible to the TB you are effectively shortening the vacuum line that "trips" the BOV. Putting it WAAAAYYY up front of the engine means a really long vacuum line and therefore a slower vacuum response. I admit, it can be a small amount of time, but we are looking for the fastest response possible, not big whooshy sound.

Again, the BOV is not only there to release pressure. It is also there to maintain air velocity in the proper direction. Having it close to the TB means the released air is still going in the right direction. And yes, air does have momentum. having it by the turbo means the air at the TB has to stop and bounce back, then when the BOV closes, it has to turn around again. Not what I would call an efficient design. Sure, the BOV at the turbo does prevent surge, but it causes havoc in the air tract after the turbo.

Venting cold air vs. warm air? Who cares, you have to release pressure no matter what which is a loss of energy (PV=nRT). The thermal air loss is very minimal and I would expect the air velocity issue would far outweigh the air temp loss issue.

Now that you have read all this and think the TB is the right answer, I am going to tell you in the real world IT DOES NOT MATTER. There is no real world performance advantage to either location. A perfectly equal empirical test will be nearly impossible to do fairly, so just put the BOV where you want to and be done with it. All the pros/cons listed would not gain you anything noticable in performance.

So have a good time and install it where you like it.

Randy


Modified by RGAZ at 9:52 AM 6/6/2003</TD></TR></TABLE>

that's one of the best reponses i've ever seen to this question

 

we are talking about air being compressed here, air cannot be more compressed in one part of the sys. than another, it is not possible, so it does not matter where you put the bov

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RGAZ &raquo;</TD></TR><TR><TD CLASS="quote">This is a good thread.

I don't think turbo parts and the physics of airflow has changed much in the last 6 years. I agree the book is getting dated, but the physics parts are still accurate.

Some points:

If you mount the BOV near the turbo OF COURSE it will be louder. It has more air pressure there since there is no drop across the piping and IC to slow the air. But does louder = more effective. No. All it means is it is releasing higher pressure air.

Also, the BOV response time is dictated by how fast it detects vacuum and begins to open. By having as close as possible to the TB you are effectively shortening the vacuum line that "trips" the BOV. Putting it WAAAAYYY up front of the engine means a really long vacuum line and therefore a slower vacuum response. I admit, it can be a small amount of time, but we are looking for the fastest response possible, not big whooshy sound.

Again, the BOV is not only there to release pressure. It is also there to maintain air velocity in the proper direction. Having it close to the TB means the released air is still going in the right direction. And yes, air does have momentum. having it by the turbo means the air at the TB has to stop and bounce back, then when the BOV closes, it has to turn around again. Not what I would call an efficient design. Sure, the BOV at the turbo does prevent surge, but it causes havoc in the air tract after the turbo.

Venting cold air vs. warm air? Who cares, you have to release pressure no matter what which is a loss of energy (PV=nRT). The thermal air loss is very minimal and I would expect the air velocity issue would far outweigh the air temp loss issue.

Now that you have read all this and think the TB is the right answer, I am going to tell you in the real world IT DOES NOT MATTER. There is no real world performance advantage to either location. A perfectly equal empirical test will be nearly impossible to do fairly, so just put the BOV where you want to and be done with it. All the pros/cons listed would not gain you anything noticable in performance.

So have a good time and install it where you like it.

Randy


Modified by RGAZ at 9:52 AM 6/6/2003</TD></TR></TABLE>

Wow... you definatley just put this great thread to a great end...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94dxt &raquo;</TD></TR><TR><TD CLASS="quote">we are talking about air being compressed here, air cannot be more compressed in one part of the sys. than another, it is not possible, so it does not matter where you put the bov </TD></TR></TABLE>

Maybe so considering a pressure vessel with no air flow, but a moving air flow through paths of varying cross sectional areas.........?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by symba &raquo;</TD></TR><TR><TD CLASS="quote">

that's one of the best reponses i've ever seen to this question </TD></TR></TABLE>

I'll second that

 

*Disclaimer* I am by no means a Turbo Expert, just sharing what I have heard.

It is my understanding that yes, the BOV's main job is to prevent turbo cavitation. The TB butterfly is not really a concern. However it is to my knowledge best to place the BOV closer to the TB because when it closes between shifts, the pressure begins to back up at the TB. Kind of like a water hose with a leak, as long as it is flowing, the leak is minimal, but when you close it off, it begins to leak heavily shortly after, not instantly.
Yes it would still work if you put it near the turbo but you would already have the length of your compressor pipe in negative flow by the time the extra pressure reaches the BOV.

*once again not an expert* a simple correction will safice

 

Pritty interesting post I must say, but I was thinking why not just put a bov right before the throttle body and a bov right after the turbo both with a separate vacum line feeds so when you let off all of the air that is at the throttle body that has momentom gets released right there and and the air that gets pushed right out of the turbo and thats stationary in the pipe gets released right after the turbo?? I'm pritty sure this would work right but the only thing I would think there would be a problem with is keeping both of them adjusted right and the vacum line feed lines being different lengths so they would both close together at the same time...

What do you guys thing of this???

Adi

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by newgsr &raquo;</TD></TR><TR><TD CLASS="quote">Pritty interesting post I must say, but I was thinking why not just put a bov right before the throttle body and a bov right after the turbo both with a separate vacum line feeds so when you let off all of the air that is at the throttle body that has momentom gets released right there and and the air that gets pushed right out of the turbo and thats stationary in the pipe gets released right after the turbo?? I'm pritty sure this would work right but the only thing I would think there would be a problem with is keeping both of them adjusted right and the vacum line feed lines being different lengths so they would both close together at the same time...

What do you guys thing of this???

Adi</TD></TR></TABLE>


i also had this idea after reading this thread, how bout 2 bov's

one right after the turbo and one right before the throttle body....than all the air in the charge pipes could escape.

 

^^^ that is exactly what i was thinking, and i have an extra blow off valve so i am going to try that, ill mount it right after the turbo and get back to yall on the effects. damn this is a great thread.