another bov recirc thread, its not what you think i promise

[justinbyrant]

so just a little background, im building my sr20 for response, im not shooting for ultra high horsepower or anything im building it for instant power and response (its a sr20 I know, if I want response I should have gone v8 I know I know) anyways so I just picked up a hks bov, im looking into buying a recirc kit for it, I didn't realize they have 2 sizes, 19mm and 29mm or .75 inch or 1.15 inch

now according to my research, theoretically running no bov at all would create better response time as there is still charged air in the system when you get back on throttle In most instances, im not going to run no bov however If I could somehow have the system still maintain 1-3 psi boost after a shift then hypothetically it should provide faster throttle response while limiting compressor surge

so the question is this, what size hose are people using to recirc? is .75 to small for 10-14 psi? is 1.15 to big? are they both to big for such low boost? im ready to order the recirc fitting and im leaning towards the 19mm one I just don't want to get it and realize its to small and is causing tons of compressor surge

[KAT-PWR]

BOVs are pretty much an all or none from what I understand. You're either equalizing the pressure to atmosphere or you attemp to contain it all in and end up with maybe a couple psi

[RB25GUY]

1.15 usually is for the higher hp applications i mean it wouldnt hurt with that said i would mount the bov on the cold side and have the recirc pipe go to your hot side air filter pipe..

[justinbyrant]

1.15 usually is for the higher hp applications i mean it wouldnt hurt with that said i would mount the bov on the cold side and have the recirc pipe go to your hot side air filter pipe..

Ya that's how I have mine set up, Im gonna buy the .75 one, I may experiment with some kind of restrictor in the hose to see if I can get it to maintain a little pressure during shifting

[spooled240]

now according to my research, theoretically running no bov at all would create better response time as there is still charged air in the system when you get back on throttle

I would disagree. Without a blow-off/bypass valve, the charged air in the system is diverted back into the compressor housing which can slow the turbo down. People have argued that the bov's are only really effective with high hp applications, but the concept is still there: Move the air around the turbo. With a proper recirculated system, you shouldn't lose any of the compressed air and you keep the turbo from slowing down in between shifts.

I've heard bad things with using the SSQV's for recirculation. I think they are too stiff and end up creating compressor surge and stalling in some cases. I had similar issues with a recirculated greddy type rs that was adjusted too tight. I now have a synapse in the cold pipe with a giant 1.25" recirculated hose to my intake and the car runs extremely well.

[justinbyrant]

I would disagree. Without a blow-off/bypass valve, the charged air in the system is diverted back into the compressor housing which can slow the turbo down. People have argued that the bov's are only really effective with high hp applications, but the concept is still there: Move the air around the turbo. With a proper recirculated system, you shouldn't lose any of the compressed air and you keep the turbo from slowing down in between shifts.

I've heard bad things with using the SSQV's for recirculation. I think they are too stiff and end up creating compressor surge and stalling in some cases. I had similar issues with a recirculated greddy type rs that was adjusted too tight. I now have a synapse in the cold pipe with a giant 1.25" recirculated hose to my intake and the car runs extremely well.

I was disregarding the compressor surge issue as I will actually be running a bov however just in terms of available air starting off with 2 or 3 psi when the throttle opens vs vacuum when the throttle opens will allow for better response, its a very fine line to walk, to be able to maintain a small amount of pressure, without creating compressor surge and without allowing the turbo to slow, If I can set it up the way im thinking idealy pressure would bleed off at a slower rate so instead of dumping everything in .5 seconds it would take double or triple that time to allow the pressure to still bleed out the bov but keeping pressure from building on the high side and pushing back on the turbo

[cotbu]

I think you should build a better system if you need 2-5psi between shifts.

I got into a debate with someone who was supposed to be from go fast bits about this very thing. My questions were along the lines of how slow would you have to shift to notice 3psi? How long would this pressure stay in the system? I wasn't really thinking of performance or response just logically.

I said something like the turbo is always spinning while the engine is running, at least it should be, so how long should it take you to build that 2 to 5psi? He said it not that you're running 5psi your running 25psi and that 5psi is already there. I don't know if he was from gfb or just bought a part from them but I was at loss for words after that.

[justinbyrant]

I think you should build a better system if you need 2-5psi between shifts.

I got into a debate with someone who was supposed to be from go fast bits about this very thing. My questions were along the lines of how slow would you have to shift to notice 3psi? How long would this pressure stay in the system? I wasn't really thinking of performance or response just logically.

I said something like the turbo is always spinning while the engine is running, at least it should be, so how long should it take you to build that 2 to 5psi? He said it not that you're running 5psi your running 25psi and that 5psi is already there. I don't know if he was from gfb or just bought a part from them but I was at loss for words after that.

its not about the pressure its about the volume, think about it this way, when the throttle plate closes the intake manifold goes into vacuum, everything is vented from the pipe, it goes into atmospheric pressure but for our sake its essentially 0, no pressure no vacuum, so when the throttle opens back up the first thing that happens is that vacuum draws the neutral air from the pipe creating a smaller vacuum through the whole system before the charge actually happens and produces boost, what I want to do is eliminate that pressure drop, or at least lessen it, its sort of a smaller example of anti lag on rally cars, you can say all you want that its only 3-5 psi and how fast can you build that pressure but its proven that it works or rally cars wouldn't replace turbos every race just for fun, its so small we cant really notice it but 100, 200, 500 gear shifts and throttle let offs per race and it adds up, it makes a difference, no matter how small a difference is a difference

[spooled240]

I was disregarding the compressor surge issue as I will actually be running a bov however just in terms of available air starting off with 2 or 3 psi when the throttle opens vs vacuum when the throttle opens will allow for better response, its a very fine line to walk, to be able to maintain a small amount of pressure, without creating compressor surge and without allowing the turbo to slow, If I can set it up the way im thinking idealy pressure would bleed off at a slower rate so instead of dumping everything in .5 seconds it would take double or triple that time to allow the pressure to still bleed out the bov but keeping pressure from building on the high side and pushing back on the turbo
I just dont see this working. If the pressurized air isnt going through the tb its gonna go back through the turbo. What it sounds like youre trying to do is have the turbo continue to create or maintain boost even when the throttle is closed, in which case an anti-lag system may be more applicable?

[cotbu]

That doesn't sound stupid to you at all?
Even if you're building a rally car.

[spooled240]

That doesn't sound stupid to you at all?
Even if you're building a rally car.
Depends on the application. Street car, yes. Race car? Probably not

[justinbyrant]

ok the only way I can think of the accurately describe my thought process on this is this, so a turbo creates x amount of boost and x amount of flow what I want to do is create some kind of way to make the bov bleed off 90% of x flow and x boost at a falling rate with the turbo

for instance, this is a very simplified example, if you let off throttle the turbo continues to spin and slow down at a rate that allows a 1psi drop every 10 seconds from 10 psi it would take said turbo to drop from a rate that in a closed system would allow for 100 seconds for the turbo to slow to a point it would no longer create boost or more accurately flow air because with a open air vent, flow is what we are looking at so what I would like to do is create a system that would allow for a complete bleed off from 10 psi in 90 seconds instead of 100 because no matter how its run and no matter what the system is doing if the turbo is creating enough flow to boost to 10 psi if the system is closed, 9 psi will never push back on the turbo, it may increase the speed the turbo slows but as long as I can find a way to keep the pressure in the pipes ahead of the falling speed of the turbo then compressor surge would not be an issue and theoretically it would maintain boost pressure in the pipes without doing any damage to any system

[justinbyrant]

if it works its a simple cheap idea that pretty much anyone can do, if it works, if not its a small waste of time but that's it, if you could increase throttle response even in the smallest amount for $30 or so and an hour of work would you do it?

[cotbu]

If this was a race car or rally car I wouldn't use the method the Australian gentlemen I was talking to described. I would rely on the anti-lag system only, but then again that's a different animal. When I shift gears boost drops to atmosphere but is right back when on throttle almost instantly, if I no lift shift which I do rarely, there is no drop.

If this turbo is a large frame on an Sr, I would probably consider a quick spool vavle.

I like building fast spooling, quick street cars that can compete with newer vehicles at the track, so beside tuning setup is just as important. The high mount vs front debate, the bov side debate, doesn't mean anything, if the system doesn't work together properly

Here the op wants repsonse, I assumed response previously was poor. You have to have a benchmark, if he does do this most likely he would have put the work in and even if there is no improvement would say that it made a difference. The idea to me doesn't make sense, when a better build setup could achieve better results. Or just shift faster!

I would like people that run no bov to chime in, my thought would be the engine just running would suck that left over boost right out if you wait to long or crack the throttle back open its gone. These things happen fast and you probably wouldn't notice.

[justinbyrant]

There are better build setups out there, antilag is one however antilag destroys turbos, im looking for something reliable, this is a track car, maybe not full blown race car but its days on the street are done, it will be used mostly for track days and a little drifting im looking for cost effective reliable ways of improving throttle response and track times, i have grown up around race cars my whole life, the idea of something small that i wont notice from in the car but improves my time is how you get ahead, im not looking to jump in the car and go "damn that was a fast run" i mean i am but thats not what this post is about

[justinbyrant]

If this was a race car or rally car I wouldn't use the method the Australian gentlemen I was talking to described. I would rely on the anti-lag system only, but then again that's a different animal. When I shift gears boost drops to atmosphere but is right back when on throttle almost instantly, if I no lift shift which I do rarely, there is no drop.

If this turbo is a large frame on an Sr, I would probably consider a quick spool vavle.

I like building fast spooling, quick street cars that can compete with newer vehicles at the track, so beside tuning setup is just as important. The high mount vs front debate, the bov side debate, doesn't mean anything, if the system doesn't work together properly

Here the op wants repsonse, I assumed response previously was poor. You have to have a benchmark, if he does do this most likely he would have put the work in and even if there is no improvement would say that it made a difference. The idea to me doesn't make sense, when a better build setup could achieve better results. Or just shift faster!

I would like people that run no bov to chime in, my thought would be the engine just running would suck that left over boost right out if you wait to long or crack the throttle back open its gone. These things happen fast and you probably wouldn't notice.

Your right they do happen fast and we probably wouldnt notice, individual data packets in a computer system happen so fast we would never even notice a minisculen increase in the speed of one data packet however if they all pick up a minuscule speed you get speed differences like that of windows 98 vs windows xp, its always the little things

[cotbu]

Honestly I'd like to see you achieve this and if it works probably implement and promote, it's kind of hard to improve on perfection, jk

You forgot the 2 other operating systems between 98 and xp not including the second edition. To a tech guy like me the differences are huge.

[justinbyrant]

Honestly I'd like to see you achieve this and if it works probably implement and promote, it's kind of hard to improve on perfection, jk

You forgot the 2 other operating systems between 98 and xp not including the second edition. To a tech guy like me the differences are huge.

I didnt forget i intentionally left them out lol the differences are huge as in the final product differences, at the core the things that caused those huge differences are small differences

A whole bunch of small supporting differences can drastically change the end result, thats what im trying to do basically i want to slowdown the let off to improve the start up, the key to to make it all work properly together

[[email protected]]

Nissan N-Attack R35 has no Bypass Valves or BOV's they eliminate the bypass valve charge pipe with a dry carbon pipe and the dry carbon intakes have no re circulation port. from what i was told when i asked about it it's because of throttle response.

[spooled240]

You know whats funny is my boost response dropped after getting the new bov and turbo. I went from a 57 trim to a 50 trim. I always thought it was my wg but it may just be the bov setup!

What would be interesting is to have a separate boost gauge on the charge pipe to see how fast the pressure drops off between shifts. Test it out with both a bov and no bov

[Kingtal0n]

if the goal is to protect the turbo,
you need a push-type or similarly fast responding bypass valve, as close to the compressor as possible. Recirculation helps by providing positive pressure to the inlet tract of the turbo but isn't necessary, unless you have a maf and don't know how to tune around it (fuel cut and so forth).

some turbos are starting to come with the bypass molded into the compressor housing.

you can monitor and data-log the maf signal for surge behavior if it is mounted close enough to the compressor (it looks like jagged spikes) SSQV style are known to be "atmospheric friendly" which just means they shut too early and cause compressor surge at moderate vacuum signals (avoid HKS unless the goal is NOT to protect the turbo as much)

[justinbyrant]

update time

so I bought both of the hks recirc fittings after trying both there is actually a far more noticeable difference than I thought there would be, the spool time between shifts is far quicker with the smaller fitting, I do get small amounts of surge with the smaller fitting but according to my research a little surge while it still does damage the turbo does such a small amount of damage that it will never make a noticeable difference in the life of the turbo and considering how little surge I have I feel like its an acceptable risk, the spool time to full boost after shifting is easily a second faster with the smaller fitting