Debate:BOV location, no idiots allowed.

 
Old 06-27-2005, 03:02 PM
  #51  
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Just my thought...placement of the BOV would be benificial having it on the hot side of the IC because if you look at it...hot air travels faster than colder denser air. By releasing it where it's hotter...it will escape faster, and also you won't have to cool it down, there by causing it's flow rate to slow down. The time it would take the colder air would not back track towards the turbo fast enough to cause any kind of surge...the most it would do is heat up under increseased pressure since it is not traveling.

Thats my theory...I'm not a physics major or anything...in fact I hate physics. I just brought the concepts that I thought would be relevant.
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Old 06-27-2005, 03:27 PM
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Default Re: (H23 EG Hybrid)

yah not trying to insult you, but cold air would actually escape faster. I dont feel like explaining it, but the temp of the air vs how fast it can escape is irrelevant.
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Old 06-27-2005, 03:33 PM
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Default Re: (DaZman69)

just install 2 blow off valves. no worries there. plus everyone will ask why you have 2, and you can counter question with, "why you just have 1?"
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Old 06-27-2005, 04:03 PM
  #54  
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Default Re: (DaZman69)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">yah not trying to insult you, but cold air would actually escape faster. I dont feel like explaining it, but the temp of the air vs how fast it can escape is irrelevant.</TD></TR></TABLE>

An explaination would be helpful...after all...this is a debate thread. Might even shine some light on something else.
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Old 06-27-2005, 09:56 PM
  #55  
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Default Re: (H23 EG Hybrid)

I'm trying to kill this thread. Let's see.

Situation A:
If we have 15 psig on one side of a pipe (say, near the turbo), but the air has to get across a few bends and an intercooler to get there, we will have 15 psig minus the pressure drop to get there. My calculation in the last page shows that this pressure is less than a couple psig in this case which involves the full flow of a medium-sized turbo. So, say 15 psig on the turbo side of the charge pipes, and 13 psig on the throttle side of the charge pipes after the pressure drop.

Situation B:
We close the throttle, IM goes into vacuum, EM pressure goes down, but charge pressure stays the same (nowhere for the air to go). We have stopped the flow in the charge pipes. If there is no flow, the pressure will be the same at the throttle side and the turbo side of the charge pipes.

We are moving from situation A to situation B. Since we don't want to get to B (so we don't stop/surge our compressor wheel), we put a BOV. If we put the BOV at the turbo, pressure at situation A will be 15 psig. If we put the BOV at the throttle plate, the air will have to move across the charge pipes, lose a couple psig and vent at 13 psig. No significant difference. Remember, the BOV will open pretty much the same in either location - it is mostly activated by the IM vacuum generated when we shut the throttle, not just by the charge pipe pressure.

So the only real difference is that if we put our BOV at the turbo, our charge pipe air may move backwards to get to the BOV (the lowest pressure zone), but when our IM opens, it will have to reverse. No big deal, air does not have much mass, thus not much inertia. If we put our BOV at the throttle, a small amount of air will have to move across the intercooler, heating it slightly. But since air flow from the turbo is almost nothing, is there really much heat soak? No.

So, what did I miss?
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Old 06-27-2005, 10:04 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">
So the only real difference is that if we put our BOV at the turbo, our charge pipe air may move backwards to get to the BOV
</TD></TR></TABLE>

no, where is it moving backwards??? THE PRESSURE IS COMING FROM THE TURBO.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by H23 EG Hybrid &raquo;</TD></TR><TR><TD CLASS="quote">

An explaination would be helpful...after all...this is a debate thread. Might even shine some light on something else.</TD></TR></TABLE>

ill provide an explanation once i'm sober
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Old 06-27-2005, 10:40 PM
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Default Re: (DaZman69)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">no, where is it moving backwards??? THE PRESSURE IS COMING FROM THE TURBO.


ill provide an explanation once i'm sober</TD></TR></TABLE>

Alright...sounds good...just trying to learn.
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Old 06-28-2005, 01:37 AM
  #58  
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Default Re: (H23 EG Hybrid)

This is a great thread. However, it seems that both sides of the debate can argue they're points until blue in the face.

The differences between location is going to have minimal affect and pretty much will come down to personal preference of BOV location. Honestly, I agree with TURNCOAT here that it's pretty much pointless to argue and a moot point on both sides. The amount of air that the turbo system as a whole is holding and the amount of air pressure created is so minimal. Eating my own words here, with out factual data and real life testing with sensative equipment, all we all can do is simply speculate and theorize on what is best.

One person commented on the vac hose from the Intake mani. If there is a worry about the BOV not opening up in time to release this supposed 'back pressure' that is going to make the turbine spin backward, use the Berinelli law and impliment a smaller diameter hose from the vac source to your BOV.
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Old 06-28-2005, 04:48 AM
  #59  
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if hot side is so good...why does every kit on the market, cept 1, run them on the cold side? this includes OE, Import, and domestic?
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Old 06-28-2005, 05:07 AM
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Default Re: (Haleiwa-Brando)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haleiwa-Brando &raquo;</TD></TR><TR><TD CLASS="quote">
One person commented on the vac hose from the Intake mani. If there is a worry about the BOV not opening up in time to release this supposed 'back pressure' that is going to make the turbine spin backward</TD></TR></TABLE>


Whoa whoa whoa...

Let's get one thing straight. The air in the charge pipes NEVER turns around or goes back towards the BOV or any of that nonsense. When you shift, your turbine is still making boost. But since your TB plate is closed, the turbo will have to work excessively hard because it's trying to over-compress more air into the closed off charge pipes.

So no matter where the BOV is, when it opens, the air will always travel away from the turbo. Whether the BOV is near the TB or turbo, the air in the charge pipes never changes direction.

Also, the problem with the long vac hose going to the BOV is that under boost, the vac line is filled with boost too. So when you shift, your intake manifold has to suck out the extra air before reaching a state of vacuum. A check valve would be a good idea here - use one to keep the BOV vac line from ever being pressurized. That should speed up the actuation.
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Old 06-28-2005, 06:33 AM
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Default Re: (EnzoSpeed)

Wow, theres a lot of stuff to read on this thread.

The closer you put the bov to the turbo the better.

Once you let off the gas, stop spooling the turbo, and blow off, the turbine wheel starts to slow down pretty fast. You want the turbo to keep moving as fast as possible to avoid lag, so would you rather blow it through a 2" pipe and right thru the bov or go through 6 feet of piping, and an intercooler and then a bov?

The latter is more restrictive, and the restriction will slow down the turbine wheel faster, because of more resitance to flow


My BOV right now is about 10 inches away from my TB and it works fine, but in every setup I do from now on, pre IC is the way to go
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Old 06-28-2005, 06:48 AM
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the idea of the bov is to alow the turbo to free flow. the sooner it can free flow air from the turbo the better the turbo will stay spooled. when the bov opens, all pressure in the charge system will drop to 0psi. if it does not, then your bov is just to small. and a turbo is about flow and will always be about flow and not pressure. why do you think two different sized turbos running the same pressure, one of them will make more power than the other. why does a mitsu turbo make power mid band then falls on its *** up on top? i vouch the bov goes on the intercooler and the most pressure vs volume is located there. ever seen how long it take to release pressure from a 20 gal tank vs a 5 gal tank?

oh yeah, air heats up as it is compressed, so would free flowing the air out the bov heat it up?
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Old 06-28-2005, 07:59 AM
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Default Re: (turbo_civic_si)

MY 2 cents....

Ever look at a SRT-4 turbo setup? the blow off valve is actually mounted on the turbo! Not saying that chrysler engineers are the greatest ever...but the germans arent too bad either.

I personally have my bov about 12" from my TB...simply because it was easier to weld a flange there....and I had access to the vacuum lines.

Full-Race never does **** just to do it. They have ME degrees...so they've put a good deal of thought into their parts...and that makes me wonder what they have to say on the matter.
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Old 06-28-2005, 11:39 AM
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Default Re: Debate:BOV location, no idiots allowed. (JonnyCoupe)

I dont know but on my car I get alot of oil in my hot side of the my intercooler and charge pipes. for daily driving you would get alot of oil going throught the BOV and I dont think that is the best for it if you want to make it last.
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Old 06-28-2005, 11:53 AM
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Default Re: Debate:BOV location, no idiots allowed. (mr.GREEN)

there should be thin film of oil if any. if you turn it like as if you are going to drain it and you have a drops coming out, you could have a problem with the turbo itself.
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Old 06-28-2005, 12:33 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTErnie &raquo;</TD></TR><TR><TD CLASS="quote">MY 2 cents....

Ever look at a SRT-4 turbo setup? the blow off valve is actually mounted on the turbo! Not saying that chrysler engineers are the greatest ever...but the germans arent too bad either.

I personally have my bov about 12" from my TB...simply because it was easier to weld a flange there....and I had access to the vacuum lines.

Full-Race never does **** just to do it. They have ME degrees...so they've put a good deal of thought into their parts...and that makes me wonder what they have to say on the matter. </TD></TR></TABLE>

Are you sure you are not looking at the waste gate instead?

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Old 06-28-2005, 03:47 PM
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I think this thread is pretty much dead. If it gets any longer, you know we are just going to get more people coming in and repeating the same crap we already went over because they are too lazy to read the previous pages.
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Old 06-28-2005, 06:30 PM
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I guess I can't get enough of this thread. Oh well, who can't resist a debate.

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

Whoa whoa whoa...

Let's get one thing straight. The air in the charge pipes NEVER turns around or goes back towards the BOV or any of that nonsense.
</TD></TR></TABLE>

Why not? If you are relieving charge pipe pressure upstream AND downstream of the BOV, the air downstream (throtle side of BOV) will have to travel backwards to the BOV - the lowest pressure zone. You are relieving pressure everywhere in the charge pipe, upstream and downstream of the BOV. You can't fight physics.

But what's the big deal with flow reversion downstream of the BOV? The air weighs next to nothing, hardly any inertia, once you open your throttle again it will travel the right way in an instant.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">
When you shift, your turbine is still making boost. But since your TB plate is closed, the turbo will have to work excessively hard because it's trying to over-compress more air into the closed off charge pipes.
</TD></TR></TABLE>

When you slam closed the throttle, your engine has maybe two or three more engine revolutions and then your EM pressure goes to nothing. With no pressure to spin the turbine, you are no longer making boost. Don't confuse charge pipe pressure with your turbo spooling. Your compressor has slowed down to almost nothing and wants to surge. BUT, you still have pressure in your charge pipes, which wants to escape out of the low pressure zone - backwards through your compressor. Your turbo might even spin backwards. You can't shift fast enough to beat this.

So you install a BOV. Your BOV is opened by the manifold vacuum and will release the pressure in your charge pipes. Wherever it is located...
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Old 06-28-2005, 06:50 PM
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I don't know about that. You're saying that in the split second it takes to shift, your turbo completely stops spinning? I just don't see that happening. I would think that the inertia of the whole rotating assembly would keep the turbo spinning for at least the time it takes to shift.
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Old 06-28-2005, 07:37 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">I don't know about that. You're saying that in the split second it takes to shift, your turbo completely stops spinning? I just don't see that happening. I would think that the inertia of the whole rotating assembly would keep the turbo spinning for at least the time it takes to shift.</TD></TR></TABLE>

The turbine has no exhaust manifold pressure to drive it. The compressor has a lot of pressure in front of it which wants to escape backwards through it. The rotating assembly weighs so little...in fact it is purposefully light to decrease spool time. Without a BOV, which opens with manifold vacuum helped by the charge pipe pressure, the turbo will slow, stop, maybe even spin backwards, but definitely put undue stress on the compressor wheel and posibly damage it's fins.

May we rename this thread "what's a BOV for". That we actually have guys talking about using two of them is an complete riot.
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Old 06-28-2005, 07:43 PM
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">

The turbine has no exhaust manifold pressure to drive it. The compressor has a lot of pressure in front of it which wants to escape backwards through it. The rotating assembly weighs so little...in fact it is purposefully light to decrease spool time. Without a BOV, which opens with manifold vacuum helped by the charge pipe pressure, the turbo will slow, stop, maybe even spin backwards, but definitely put undue stress on the compressor wheel and posibly damage it's fins.

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


No doubt. But the fact is that we do use blow-of valves, so while there is no exhaust pressure spinning the turbine, there is also not much pressure pushing back on the cold side.
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Old 06-28-2005, 08:09 PM
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Default Re: (EnzoSpeed)

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


Also, the problem with the long vac hose going to the BOV is that under boost, the vac line is filled with boost too. So when you shift, your intake manifold has to suck out the extra air before reaching a state of vacuum. A check valve would be a good idea here - use one to keep the BOV vac line from ever being pressurized. That should speed up the actuation.</TD></TR></TABLE> No pressure in your BOV's vaccum line would cause the valve to open under boost, trust me I have had the problem on the dyno. Top dog tuner took the boost plot using said vaccum line.

They are not solely vacuum actuated the boost pressure it self plays apart in both releasing the valve obviously and also seating it in place via the vacuum line.
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Old 06-29-2005, 02:19 AM
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^^^ Good call, I forgot about that.
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Old 06-30-2005, 08:14 PM
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FLr...if you've even seen a SRT-4 turbo you'd know that the bov is on the compressor cover. No I'm not an idiot. I know what a wastegate is... I'm QUITE QUALIFIED and understand the terminology that I'm using. The bov is ACTUALLT PART OF THE COMPRESSOR COVER.



see the blue Mopar bov upgrade machined piece? Thats where the bov is. The wastegate actuator is taken off in this pic, but you can still see the swing arm and the two unused mounting bolts on the compressor cover. Its a reverse spinning 16g.
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Old 07-01-2005, 12:59 PM
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Default Re: (RTErnie)

actually the blow off valve is not the machined blue peice. its the silver peice that screws to it. the blue peice is merely a diverter plate that makes it vent to atmosphere instead of recirculation.
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