DaZman69

My question is where is the best place to locate the BOV. Most of you are gonna spit out "close to the throttle plate." But I was thinking about it and I dont think that is that best spot. First off, I really dont think it matters that much. I doubt the position of your BOV is going to effect your turbo life whatsoever. But in theory I think it would be better closer to the turbo. I mean the goal of the BOV is to relieve the pressure surge in the charge pipes for the sake of the turbo. It might suddenly reverse rotation. So why put the relief valve so far away from the turbo??

I wanna hear other people's views of why you think it should be near the throttle plate.

093turbo16

iTrader: (2)

The easiest spot to put it is usually my vote. BUt why do you think people mount them on their intercooler, atleast on most drag cars they are pre intercooler or on the inlet side. So IMO, if you aren't running insane boost, just put it on the charge pipe before the TB.

s1ngle

iTrader: (1)

youre right, its better closer to the turbo. Main reason being, that it keeps the rest of the system, including the IC, pressurized, and allows you to keep your turbo RPMs up for more instantaneous boost when you resume throttle.

DaZman69

ah i didnt know the drag guys were doing it like that.

what do you mean inlet side? before the turbo? (i hope you didnt mean that)

DaZman69

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s1ngle &raquo;</TD></TR><TR><TD CLASS="quote">youre right, its better closer to the turbo. Main reason being, that it keeps the rest of the system, including the IC, pressurized, and allows you to keep your turbo RPMs up for more instantaneous boost when you resume throttle.</TD></TR></TABLE>

wow i thought it was unanimous that everybody thought it was best to put it close to the throttle. Atleast this will educate people

seen4ever

with my backdoor intercooler i just had made with a garrett core, garrett included instructions which said, do not place BOV before intercooler. So i followed thier instructions and placed it on the charge pipe. I was going to put it where alot of the Full-Race BOVs go on the hot side of the intercooler, but I figured garrett knew a thing or two.

I don't really understand how having the BOV would keep the IC pressurized, as the trottle body closes, air has no where to go and I know when the big *** Tial BOV opens it easily gets out all pressure in the system.

ScottEK

In Maximum Boost I believe it says to put it before the intercooler because otherwise you would make the intercooler work harder (heating it up) for no reason because you are expelling that cooled down air.

s1ngle

iTrader: (1)

well that too, thats another benefit.

the rest of the system after the BOV will stay more pressurized, including the intercooler and upper charge pipe. when the BOV opens the air leaving it will be pushed thru by the turbo itself as it slows down. Yore far less likely to lose nearly as much pressure in the rest of the system.

AngelTeg

While in the real world it makes little to no difference... from a technical perspective, you're right, you want it as close to the turbo as possible.
-Mike

USDM 4G VTEC

a BOV should be placed about 12 inches before the trotle body
reason behind it is so that when the butterfly closes and the pressure starts to reverse towards the turbo, as soon as the surge takes place, the BOV will bleed the pressure out and keep it as far form the turbo as possible, making sure the turbo doesnt surge and brakes

Dunc

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s1ngle &raquo;</TD></TR><TR><TD CLASS="quote">youre right, its better closer to the turbo. Main reason being, that it keeps the rest of the system, including the IC, pressurized, and allows you to keep your turbo RPMs up for more instantaneous boost when you resume throttle.</TD></TR></TABLE>

Makes sense and seems reasonable to me.....

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by USDM 4G VTEC &raquo;</TD></TR><TR><TD CLASS="quote">a BOV should be placed about 12 inches before the trotle body
reason behind it is so that when the butterfly closes and the pressure starts to reverse towards the turbo, as soon as the surge takes place, the BOV will bleed the pressure out and keep it as far form the turbo as possible, making sure the turbo doesnt surge and brakes</TD></TR></TABLE>

But, this makes more sense I think. If you think about it, it seems like you can either have:

1.)Less of a loss in boost in between shifts (at least it's claimed)
or
2.) Less chance of compressor surge

Hmmmm....which one would you rather have? I'll take a lesser chance of surge anyday over a 0.5 second head start to getting back to full boost.

gyrluknouwantme

^Agreed. This is a really good discussion, however. Both sides seem to have very good technically sound opinons. I'd love to hear some more perspectives, though!

s1ngle

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by USDM 4G VTEC &raquo;</TD></TR><TR><TD CLASS="quote">a BOV should be placed about 12 inches before the trotle body
reason behind it is so that when the butterfly closes and the pressure starts to reverse towards the turbo, as soon as the surge takes place, the BOV will bleed the pressure out and keep it as far form the turbo as possible, making sure the turbo doesnt surge and brakes</TD></TR></TABLE>

this is not true. If you understand the nature of air and flow of things in general, such as air, oil, gas, electricity, youd understand that its not like the air is traveling along, hits the throttle body, and decides to turn around and meander back to the turbo.

Think of a liquid. You push water in one end of a hose, and it comes out the other end. If you have a hose full of water, you push water in one end, and what water comes out the other end? not the water you just pushed in, its the water thats already in there. This would refute your argument if you agree with this, because the pressure is constant throughout the charge system, it wouldnt matter in terms of compressor surge whether you do it a foot from the turbo or a foot from the throttle body, either way it relieves the pressure from the system.

sorry about the book.

EnzoSpeed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">

wow i thought it was unanimous that everybody thought it was best to put it close to the throttle. Atleast this will educate people</TD></TR></TABLE>


I've never heard of that before. Actually, I assumed it was unanimous that everyone would say "as close to the turbo as possible."


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s1ngle &raquo;</TD></TR><TR><TD CLASS="quote">

this is not true. If you understand the nature of air and flow of things in general, such as air, oil, gas, electricity, youd understand that its not like the air is traveling along, hits the throttle body, and decides to turn around and meander back to the turbo.

Think of a liquid. You push water in one end of a hose, and it comes out the other end. If you have a hose full of water, you push water in one end, and what water comes out the other end? not the water you just pushed in, its the water thats already in there. This would refute your argument if you agree with this, because the pressure is constant throughout the charge system, it wouldnt matter in terms of compressor surge whether you do it a foot from the turbo or a foot from the throttle body, either way it relieves the pressure from the system.

sorry about the book.</TD></TR></TABLE>


Agreed. Obviously the air isn't flowing back and forth in the chare pipes. I don't see why you guys don't understand this

I can't think of any benefit at all of having the BOV near the TB.

JonnyCoupe

Only difference with air and water is that air is compressible so you wont instantly release pressure like water where ever the dumping is taking place. The air almost has a shockwave effect like a spring coil where it 'uncompresses' this obviously takes time, so id argue near turbo is better as then the pressure post compressor will lower FASTER and hence the compressor is subject to less duration of pressure differential between compressor inlet and outlet that serves to slow and stall it.

BEfore the IC is ideal too, no point dumping cold air.

EnzoSpeed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JonnyCoupe &raquo;</TD></TR><TR><TD CLASS="quote">
BEfore the IC is ideal too, no point dumping cold air. </TD></TR></TABLE>


Wow, good point

frago

Wouldn't you want it at the end close the TB... in the direction of flow?

Also you wouldn't want the vacuum line going to the BOV to be too long. The longer the line the less velocity it has to pull open the valve.

Dunc

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JonnyCoupe &raquo;</TD></TR><TR><TD CLASS="quote">BEfore the IC is ideal too, no point dumping cold air. </TD></TR></TABLE>

I agree, good point.....but as I was reading I started thinking to myself:

Why would it matter at all where the BOV is located in terms of surge and pressurized pipes are concerned.

1.)<U>Pretend</U> that when the valve opens (12" from TB), you lose the pressure from the TB to the BOV...and <U>pretend</U> the rest of the system is still pressurized. When it closes you need to re-pressurized that 12" again.
2.) Think of the same situation, but reverse it if the BOV is near the turbo.....
Either way, you are still going to have to re-pressurized some length of piping before you can start boosting again. Soo now the only reason I am seeing to put it before the intercooler is from what JonnyCoupe said, "BEfore the IC is ideal too, no point dumping cold air. "

s1ngle

iTrader: (1)

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

Either way, you are still going to have to re-pressurized some length of piping before you can start boosting again. Soo now the only reason I am seeing to put it before the intercooler is from what JonnyCoupe said, "BEfore the IC is ideal too, no point dumping cold air. "</TD></TR></TABLE>

I would say this is not entirely true. Think about it this way, why are you blowing off air? its because even thought he throttle plate is closed, the turbo is still spinning down, still compressing air (although it is slowing down). So the turbo is in fact forcing the air out, in a sense. And its forcing it out in the direction going fromt he turbo to the throttle body. If you have the BOV close to the turbo, MOST of the air forced out of the BOV is going to be coming directly from the turbo, while the rest of the system will remain more pressurized than if the BOV is all the way by the TB, then the whole length of the charge system between the turbo and the BOV will decrease in pressure.

MRturbo

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

I agree, good point.....but as I was reading I started thinking to myself:

Why would it matter at all where the BOV is located in terms of surge and pressurized pipes are concerned.

1.)<U>Pretend</U> that when the valve opens (12" from TB), you lose the pressure from the TB to the BOV...and <U>pretend</U> the rest of the system is still pressurized. When it closes you need to re-pressurized that 12" again.
2.) Think of the same situation, but reverse it if the BOV is near the turbo.....
Either way, you are still going to have to re-pressurized some length of piping before you can start boosting again. Soo now the only reason I am seeing to put it before the intercooler is from what JonnyCoupe said, "BEfore the IC is ideal too, no point dumping cold air. "</TD></TR></TABLE>

DaZman69

one thing i think everybody is forgeting is that a BOV is a relief valve. It doesnt let all the pressure out, it just lets the surge out. Its gonna close back up if the pressure in the charge pipes go down to what your boost pressure is. So pretty much anywhere you put it your not gonna "lose pressure."

But<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s1ngle &raquo;</TD></TR><TR><TD CLASS="quote">

I would say this is not entirely true. Think about it this way, why are you blowing off air? its because even thought he throttle plate is closed, the turbo is still spinning down, still compressing air (although it is slowing down). So the turbo is in fact forcing the air out, in a sense. And its forcing it out in the direction going fromt he turbo to the throttle body. If you have the BOV close to the turbo, MOST of the air forced out of the BOV is going to be coming directly from the turbo, while the rest of the system will remain more pressurized than if the BOV is all the way by the TB, then the whole length of the charge system between the turbo and the BOV will decrease in pressure.</TD></TR></TABLE>

exactly why I started the thread and thought it should be placed near the turbo.

lkailburn

^^paul i think you nailed it perfectly. i just put it near the tb for simplicity sake. this is just a daily driver but for all out performance close to the turbo, pre ic is ideal

Dunc

yea I can understand your argument about the relief valve idea and losing pressure, etc. I guess I can see both sides of the story. Sooo I guess someone needs to do some scientific research/experiments to back up the claim of: the piping will be slighter more pressurized if the BOV is near the turbo. Numbers speak louder than words.

kblus711

education at its best

turncoat

Okay, let's calculate this out. Here's a some online tools some of you will have fun with, I use it at work since it's a lot quicker than pulling out the Bernoulli equation.

http://www.freecalc.com/gasfram.htm

Basically for 400 CFM, 15 psig inlet pressure and 200 deg F temp (which is way more flow than what will be there with throttle closed), the entire piping system has a diddly 0.75 psig pressure drop. Most intercoolers (unless ridiculously undersized) will drop less than 1 psig at this flow. If you like, I can calculate this out...

Anyway, it's a combined 1.75 psig drop in the piping system, which means you would measure 15 psig at the compressor exit of the turbo, and 13.25 psig at the throttle plate, at full flow. But remember, you won't be anywhere near this flow when the throttle plate is closed and all air flow is going through your blow-off valve, since there is little to no exhaust gas to spool the turbo. To put this into perspective, at the same conditions at 100 CFM, the total system pressure drop in this case will be less than 0.1 psig. Although I used a static calculation for a dynamic system (i.e. dynamic since the flow is dropping dramatically as the turbo loses speed from having no exhaust to drive it), hopefully you get the picture. So basically pressure drop is a non-factor in blow-off valve placement.

So this leaves the only other factor being heat soak in the intercooler. If the BOV is after the intercooler, yes, a small amount of heated air flow will have to move across the intercooler and transfer it's heat to get the the BOV. If the BOV was before the intercooler, it would eject the hot air, there would be no airlow across the intercooler, and thus give it a 1/2 second to cool down. IMO, there will be very little flow in either case (yes, still pressure, but very little flow) and thus very little heat to transfer and soak into your intercooler. Again, I'd say this would have very little factor in BOV placement.

Someone could say that the pressure shock wave caused you the sudden closing of the throttle plate can harm your turbo (bend the compressor wheel fins or snap the shaft, I guess), so the BOV should be at the throttle to vent this where it starts. BUT, the intercooler, typically being such a huge volume and with large chambers (endtanks) acting as massive baffles, should reduce any pressure wave effect (assuming you have a BOV). Becasue of this, I'd have to assume it would basically act like a muffler on your intake to smooth out any disturbances.