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Plumbing Back Atmo Bov's

ZRBE

By ZRBE,
in Engines & Forced Induction

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GTSBoy Grand Master

GTSBoy

Posted
Posted

"air that was previously flowing towards the TB does in fact have to turn around and flow the other way in order to decrease the pressure in the tract."

I put it forward, there's no need for the air to reverse and flow the other way. Consider this - throttle shuts, airflow into engine stops as throttle plate has now blocked path. Compressor still spinning and pumping air into piping which is now not flowing. BOV located straight after compressor on intercooler piping lets this air out rather than pressure building and pushing against compressor. So the airflow would be effectively stopped, pressure remains the same, and any incoming air would continue to flow the same way, just be diverted straight out the BOV rather than continuing through towards the engine. Get back on throttle and more boost pressure is already there as it hadn't been depressurised in front of throttle plate.

To be honest i think the difference between putting it just before throttle, or just after compressor, would be sweet F.A, in most cases, but it makes sense to me to put it in front of compressor. For another reason, when no longer being driven by the turbine (under closed throttle) the compressor will slow down alot more trying to drive air through the intercooler rather than allowing it to vent out straight away before passing through the I/C.

Obviously this is based on zero hours of research and development by me :P and I'm sure auto manufacturers might have given it at least a few hours testing.....

Nup. Inlet tract at 20 psi. Throttle slams shut and turbo still piling air in, sure. But if you watched a boost gauge connected to the inlet tract (rather than the plenum) during such an event and you will see the pressure fall a long way below the boost pressure it was running at. That only occurs because the air goes out through the hole. The air has to come from everywhere and will flow from the furthest points towards the hole.

Air has mass and inertia. Making it stop and turn about to flow back the other way is inefficient and does work on the air - which ultimately ends up as either heat, or extra pressure (in the form of pulses running up and down the inlet tract).

Again, I must stress that I'm not maintaining that it is the most important consideration in "designing" such a system. But is apparently considered important enough by people who were paid to do it to do it in a particular way, rather than the apparently easier and cheaper alternative.

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SargeRX8
SargeRX8

You dont need to bash it. When on boost theres 12 or what ever boodt you're running coming through the silicone hose on your bov pushing down on it to help keep it shut. So as long you've got some spr

GTSBoy
GTSBoy

Yes it is that easy.....except that you have to be able to bolt it all together once it is welded up. So a little thought during the "design" phase can save you a lot of swearing later. Main point o

shaunus
shaunus

Just take the plastic piece out from the vent on the SSQV. Will be much quieter and not make that high pitched whistle. I also couldn't stand the SSQV sound. This worked. Try it.

SargeRX8 Grand Master

SargeRX8

Posted
Posted

Can you put a pic up of your engine bay?

Also a while back when I was intending to go high mount ext gate turbo I planned on using parts I found in the US which were a 2" flex pipe which was designed as a kit for external gate setups. The way it looked was pretty good. One end had a bung which was welded to a piece of pipe from your gate and another bung welded into your exhaust and was at a 45 degree angle(they came in different angles). Then you use the hose which was x cm long and attached one end to your WG and the other to the bung in the exhaust. Good thing about the setup was you could undo it all in a matter of minutes and go straight to a atmo vent setup if you wished. The guy who was selling them stopped and I have never seen anything close to them since. This was about 2 years ago.

shaunus Enthusiast

shaunus

Posted
Posted

Weld the adapter underneath the intercooler pipe next to the intake, weld nipple to side of intake bend. Attach BOV to IC piping, run return to the nipple on intake pipe. Any metal/fab shop could complete the welding for a carton.

  • Like 1
ZRBE Experienced

ZRBE

Posted
  • Author
Posted

Weld the adapter underneath the intercooler pipe next to the intake, weld nipple to side of intake bend. Attach BOV to IC piping, run return to the nipple on intake pipe. Any metal/fab shop could complete the welding for a carton.

No worries, my pop can weld. So I'll ask him to see if he can sort something out.

Thanks again guys :)

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hardsteppa Grand Master

hardsteppa

Posted
Posted

got to say, I look forward to your posts GTSBoy, you're certainly a learned fellow. Just posted something in the braking section I'd like your thoughts and input on, if you care to do so.

Re above "But if you watched a boost gauge connected to the inlet tract (rather than the plenum) during such an event and you will see the pressure fall a long way below the boost pressure it was running at. That only occurs because the air goes out through the hole."

agreed, this being the point of a BOV to release pressure.

"The air has to come from everywhere and will flow from the furthest points towards the hole." if you looked at a smoke test though, wouldn't you see it start to flow through from the area immediately located from the source of the escape route (BOV)? So if you put it as close to the compressor as possible (with the BOV intended to prevent reversion and damage to the compressor) it would reduce pressure in this area first thus preventing reversion and damage to turbo.

I don't claim to have done the research and testing to make this theory foolproof by any means; as we all know from doing basic modifications from day one of owning a turbo car, OEM specs can be improved upon and you got to wonder how much convenience and budgets play a part in R&D and the mass-marketed final product.

GTSBoy Grand Master

GTSBoy

Posted
Posted

if you looked at a smoke test though, wouldn't you see it start to flow through from the area immediately located from the source of the escape route (BOV)? So if you put it as close to the compressor as possible (with the BOV intended to prevent reversion and damage to the compressor) it would reduce pressure in this area first thus preventing reversion and damage to turbo.

Pressure pulses in air travel at the speed of sound. At normal atmospheric pressure and temperature, that's 300m/s or so. It's a bit different with hotter high pressure air, but it's still bloody fast. The effect of opening the BOV is felt everywhere in the inlet tract within a couple of milliseconds of it cracking open. Sure, the first air to escape is the air closest to the BOV, but all the air in the tract starts to move towards the BOV as soon as it's open. Well, except for the air near the TB which has to stop and turn around first, but even that doesn't take very long.

hardsteppa Grand Master

hardsteppa

Posted
Posted

you're kind of killing your own arguement there though, if "The effect of opening the BOV is felt everywhere in the inlet tract within a couple of milliseconds of it cracking open." then the assertion "The BOV should be physically located close to the throttle body" - a cpl of milliseconds, it wouldn't matter where you put it, and so you could mount it whereever was most convenient and any performance advantage would be negligible if we're talking a couple of milliseconds.

Ben C34 Grand Master

Ben C34

Posted
Posted

you're kind of killing your own arguement there though, if "The effect of opening the BOV is felt everywhere in the inlet tract within a couple of milliseconds of it cracking open." then the assertion "The BOV should be physically located close to the throttle body" - a cpl of milliseconds, it wouldn't matter where you put it, and so you could mount it whereever was most convenient and any performance advantage would be negligible if we're talking a couple of milliseconds.

So why did nissan mount it where they did? They could have put it heaps closer to the inlet pipe that its plumbed back to, and eliminated the metal pipework on the return side. They have gone to the extra trouble of mounting it as close to the throttle for a reason.

GTSBoy Grand Master

GTSBoy

Posted
Posted

you're kind of killing your own arguement there though, if "The effect of opening the BOV is felt everywhere in the inlet tract within a couple of milliseconds of it cracking open." then the assertion "The BOV should be physically located close to the throttle body" - a cpl of milliseconds, it wouldn't matter where you put it, and so you could mount it whereever was most convenient and any performance advantage would be negligible if we're talking a couple of milliseconds.

No I'm not. The pressure signal is felt quickly. The result, being the decel followed by accel in the other direction takes a lot longer and actually triggers reverbatory pressure pulses that don't need to be there. If the BOV is located at the end of the pipe towards which the air is already flowing, then the air just keeps going that way and dumps out the BOV with no upset.

But, again, I must stress that apart from it being obvious that some serious engineers think it's a good idea to locate it near the TB, it's not likely to be the be all and end all in the decision you make about where to stick the BOV. If it were me doing some plumbing design for a new engine in a new engine bay or modding up an engine in an existing engine bay, I'd try to keep the BOV near the TB, but if I couldn't I wouldn't get liver cancer from the stress of it.

ZRBE Experienced

ZRBE

Posted
  • Author
Posted (edited)

Hey guys, I'm having trouble finding an adaptor plate for my 'Kompact Plumback'

But I do have the spec sheet (of the BOV) with the exact measurement of the base ect.

Will an exhaust shop be able to make up an adaptor plate for it?

If I hand them this sheet.

image-50.jpg

Edited by ZRBE
scotty nm35 Grand Master

scotty nm35

Posted
Posted

An exhaust shop, no.

Any fabricator could make one. Does it need to be alloy or stainless?

The plate can be removed off the bov I am fairly sure, that way you could use a round hose instead.

ZRBE Experienced

ZRBE

Posted
  • Author
Posted

An exhaust shop, no.

Any fabricator could make one. Does it need to be alloy or stainless?

The plate can be removed off the bov I am fairly sure, that way you could use a round hose instead.

My cooler pipe is stainless. So, I guess the adaptor stainless as well?

But if I can remove the plate from bottom of the BOV and just use a hose to connect it to the cooler pipe. Then I might do that, sounds easier and probably a better seal..

ZRBE Experienced

ZRBE

Posted
  • Author
Posted (edited)

Personally, just removed the SSQ and "cap" it off.

BTW the BOV will be the last thing they look for after they see your turbo... :action-smiley-069:

Well I will be removing the SSQ altogether and capping it.

Then putting in the TurboSmart one in. On that bend closest to intake.

Haha the first time I was pulled over in my 32 the cop knew P Platers could NOT drive turbos (so did I) but looked straight at my turbo.. :P

Edited by ZRBE
  • 2 weeks later...
  • 1 month later...
ZRBE Experienced

ZRBE

Posted
  • Author
Posted

Well I found a welder.. Ended up using the turbosmart kompact..

I have a really bad feeling I might of set it up incorrectly.... :/

I'll post a pic up in a sec, I know that hose is kinked I have bought a new hose that won't kink.

So that's sorted..

Just wondering with the skinny black hose ontop of the BOV. Does that connect to the back of the throttle body?

I know it's waaaay too long haha I need to cut it shorter.

Appreciate the help guys!! :)

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