Debate:BOV location, no idiots allowed.

 
Old 06-23-2005, 06:50 PM
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Default Re: Debate:BOV location, no idiots allowed. (turncoat)

i guess canadaians do know what theyre talking about
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Old 06-23-2005, 07:23 PM
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Default Re: Debate:BOV location, no idiots allowed. (turncoat)

I don't think there would be a huge advantage but it must help lag a little having it on the hot side or else the drag racers wouldn't do it.
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Old 06-23-2005, 07:43 PM
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Default Re: Debate:BOV location, no idiots allowed. (turbozxi)

im thinking about place mine on the hot side near the turbo. but i might run dual turbonetics raptor bov's and im trying to figure out how to place those. maybe 180* from each other?
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Old 06-23-2005, 07:53 PM
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Default Re: Debate:BOV location, no idiots allowed. (wantboost)

Hmm ok well let me throw this out there. Im in no way a professional on this but there seems to be alot of discussion as if the air acts as water when moving throght the pipes.

When we make boost that means everything is pressurized correct? Therefore from the tb all the way back to at least the intercooler there is pressure, no gaps of air.

Therefore the air "right at the throttle body" doesnt come back like a slinky, the whole pressurized system as a whole wants to get out (read: go back to the turbo) so this would mean to get the whole system of pressure out the best would be at the end of the system or closest to the turbo. This is all what i see in my mind. So take it for what its worth. We are debating so im just being devils advocate
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Old 06-23-2005, 08:06 PM
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Default Re: Debate:BOV location, no idiots allowed. (turncoat)

since when are we concerned with pressure drop based solely on the piping and intercooler itself? what youre saying based on your calculations is that the pressure drop in just the piping and intercooler itself is a non concern. When you bring a relief valve into the situation it all changes.

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

</TD></TR></TABLE>
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Old 06-23-2005, 08:37 PM
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Default Re: Debate:BOV location, no idiots allowed. (s1ngle)

I've been watching this most of the day...it's now late, and it's making my brain hurt haha. See ya in the morning.....with a fresh mind to help out with this.
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Old 06-24-2005, 01:37 PM
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Default Re: Debate:BOV location, no idiots allowed. (Dunc)

there is no shockwave with air...

if it was water there would be...because it has about 400 times its mass and is not compressible.

ever heard a small bang when you quickly close a water valve of some sort in your house? thats a shockwave. It is especially noticable on high pressure/flow hydraulic systems. Air does not do that. Well technically it does, but its so small that it is not a factor whatsoever.

If there was a shockwave, then it would be best to place it near the TB.
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Old 06-24-2005, 01:43 PM
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Default Re: Debate:BOV location, no idiots allowed. (DaZman69)

if there was a shockwave (which there could be) wouldnt it not matter where you put the BOV as long as you didnt let hte shockwave get to the turbo?
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Old 06-24-2005, 02:15 PM
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Default Re: Debate:BOV location, no idiots allowed. (DaZman69)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">ever heard a small bang when you quickly close a water valve of some sort in your house? </TD></TR></TABLE>


Lol, yeah! I never thought about what that noise was until now.
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Old 06-24-2005, 03:09 PM
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Default Re: Debate:BOV location, no idiots allowed. (s1ngle)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s1ngle &raquo;</TD></TR><TR><TD CLASS="quote">if there was a shockwave (which there could be) wouldnt it not matter where you put the BOV as long as you didnt let hte shockwave get to the turbo?</TD></TR></TABLE>

there is definatly not a shockwave. The shock wave would be caused by the sudden mass of the air comming to a hault and not having the ability to compress itself (just like water) but it can compress itself and there is not enough mass to cause one of any significance anyway.

What happens to a space shuttle when it enters the earths atmosphere...there's a lot of resistance and it slows down a lot. No actual shock or thud.

what happens when a spaceship runs into the ocean at mach 30. it would be broken down to invdividual electrons, nuetrons, and protons before it got 10 feet deep. not really lol, but pretty damn close.

if god himself decided one day hey lets have this guys car create a shockwave in his charge pipes....you'd wanna stop it where it starts. The bov does not open instantly.


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Old 06-24-2005, 03:29 PM
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Default Re: Debate:BOV location, no idiots allowed. (DaZman69)

What a debate!
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Old 06-24-2005, 07:29 PM
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Default Re: Debate:BOV location, no idiots allowed. (H-T)

best of both worlds, run dual BOVs, one right in front of the TB and one right in front of the turbo outlet
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Old 06-24-2005, 08:20 PM
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Default Re: Debate:BOV location, no idiots allowed. (gyrluknouwantme)

I don't see why this is a debate. The bottom line is that a BOV lets off the extra pressure that would otherwise harm your turbo. So if the BOV is near the throttle body, even though it still relieves the excess pressure, it's going to take longer for that pressure relief to be seen at the turbo.

Mounting the BOV near the turbo means that when the valve opens, the pressure relief at the turbo will be instant.

So mounting the BOV near the turbo is best. Mounting it closer to the throttle body is not as ideal, but the difference is minimal. Either way though, mounting it near the throttle body isn't ideal in either case.

The "debate" should be whether or not mounting the BOV near the turbo is worth the extra mounting hassle or extended vacuum line. There is no debate that concerns mounting the BOV near the throttle body as a good thing.
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Old 06-24-2005, 08:23 PM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

I think there must be some equilibrium point in BOV placement.

Near the TB = slower pressure releif once the valve opens, but faster valve opening because the vacuum line will be short.

Near the turbo = faster pressure relief once the valve opens, but slower valve opening because the vacuum line will likely have to be longer.


So it seems that the ideal mounting point would be where the vacuum line can be made reasonably short, but where the BOV would also be as close to the turbo as possible.
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Old 06-24-2005, 09:23 PM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

i have no vacuum lines going to my bov, not all are actuated by vacuum
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Old 06-24-2005, 10:25 PM
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Default Re: Debate:BOV location, no idiots allowed. (DaZman69)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">i have no vacuum lines going to my bov, not all are actuated by vacuum</TD></TR></TABLE> huh ? What kind of BOV do you use

Your forgetting about having to refill the charge pipe on the cold side with air and cold air at that Enzospeed if placing the BOV on the cold side.
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Old 06-24-2005, 11:05 PM
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Default Re: Debate:BOV location, no idiots allowed. (turbozxi)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Your forgetting about having to refill the charge pipe on the cold side with air and cold air at that Enzospeed if placing the BOV on the cold side.</TD></TR></TABLE>


Yeah, but does that really matter? Who cares if the air comes out before or after the intercooler. It's not like the turbo is going to have to work extra hard to make more cold air to substitute what you let out.
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Old 06-25-2005, 12:58 PM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

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


Yeah, but does that really matter? Who cares if the air comes out before or after the intercooler. It's not like the turbo is going to have to work extra hard to make more cold air to substitute what you let out.</TD></TR></TABLE> It will most likely take a little longer to refill the cold side of the piping with air generally being a longer tract and also having to go through the intercooler to be reached, the air on the cold side already has been chilled as well. Anyway I am switching my BOV on my s14 on tuesday so will be able to tell if there was any real difference...
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Old 06-25-2005, 01:34 PM
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Default Re: Debate:BOV location, no idiots allowed. (DaZman69)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 &raquo;</TD></TR><TR><TD CLASS="quote">i have no vacuum lines going to my bov, not all are actuated by vacuum</TD></TR></TABLE>

kneegrow what?? I REALLY wanna know what bof you're using.


Don't tell me it's one of those ebay electronic one, that one does not require any vacuum.
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Old 06-25-2005, 02:07 PM
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Default Re: Debate:BOV location, no idiots allowed. (turbozxi)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbozxi &raquo;</TD></TR><TR><TD CLASS="quote"> It will most likely take a little longer to refill the cold side of the piping with air generally being a longer tract </TD></TR></TABLE>

But it doesn't matter where you let the air out, the same amount of air will always exit the BOV because the pressure throughout the whole piping system is uniform (except for the slight pressure drop from the intercooler). It won't take longer to refill one section as opposed to another.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
the air on the cold side already has been chilled as well. </TD></TR></TABLE>

Yeah, but it doesn't matter. Unless you are worried about heat soaking your intercooler. Maybe if you were in stop and go traffic and had to shift a lot without getting a lot of air accross the front of the intercooler. Then constantly letting out cold air and having to cool additional incoming air might heat soak your intercooler. But I seriously doubt it.


I think I made up my mind for the area around the cold side of the IC for BOV placement
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Old 06-26-2005, 02:56 PM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed &raquo;</TD></TR><TR><TD CLASS="quote">But it doesn't matter where you let the air out, the same amount of air will always exit the BOV because the pressure throughout the whole piping system is uniform (except for the slight pressure drop from the intercooler). It won't take longer to refill one section as opposed to another.
</TD></TR></TABLE>

Which isnt the case once we get into the the flow losses at bends,

So there will be more air exiting the BOV post compressor than the TB due to the higher pressure. Also this helps to initialise the pressure drop much quicker, air being compressible means the pressure post turbo if the air is dumped at the TB will take longer to reduce and allow a larger pressure spike, both these effects means the compressor with slow more due to the higher delta P across the compressor blades.

Im sold on IC hot side now Plus it sounds louder outside
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Old 06-26-2005, 05:28 PM
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Default Re: Debate:BOV location, no idiots allowed. (JonnyCoupe)

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

Which isnt the case once we get into the the flow losses at bends,

So there will be more air exiting the BOV post compressor than the TB due to the higher pressure. Also this helps to initialise the pressure drop much quicker, air being compressible means the pressure post turbo if the air is dumped at the TB will take longer to reduce and allow a larger pressure spike, both these effects means the compressor with slow more due to the higher delta P across the compressor blades.
</TD></TR></TABLE>


That's basically the "pro" I listed to having the BOV near the turbo. It relieves the pressure more quickly once the valve opens.

But as I said, you also have to take into account that having the BOV near the hotside of the intercooler will most likely mean a long vacuum hose. And who cares if the valve releases the pressure quicker when it takes longer to open? A faster valve open is more important because any delay in the valve actuation means that FULL pressure is pushing back on the turbo.
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Old 06-27-2005, 07:48 AM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

Good point about the vac hose, however when you compare the volumes in each pipe, ie charge and vac the vac pipe length really is negliable. IMO
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Old 06-27-2005, 02:28 PM
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Default Re: Debate:BOV location, no idiots allowed. (JonnyCoupe)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JonnyCoupe &raquo;</TD></TR><TR><TD CLASS="quote">Good point about the vac hose, however when you compare the volumes in each pipe, ie charge and vac the vac pipe length really is negliable. IMO</TD></TR></TABLE>

I don't understand what you mean. What's the vac pipe?
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Old 06-27-2005, 02:36 PM
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Default Re: Debate:BOV location, no idiots allowed. (EnzoSpeed)

<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 understand what you mean. What's the vac pipe?</TD></TR></TABLE>

he means there such a small volume of air in the vac line that its so fast its not important
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