Stillway FD track car….and name that BOV?
#26
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Willub and company you definitly made a point there im going to have to go with your theory and agree w/ you..
Alot the 9 sec rx7's I know about have custom or race bov's..
Alot the 9 sec rx7's I know about have custom or race bov's..
#29
development
Originally Posted by Farhan
Your sentences don't make sense anyways so I wouldn't be talking.
Originally Posted by RE-Amemiya7
I am at a loss why any company would stick ungodly amounts of money into a car and only to have the boosted air be forced back into the turbine, when the plates are closed, damaging the turbine. Is there a performance advantage to this?
Originally Posted by willub and company
I'm going to have to play devil's advocate here, you are contradicting yourself. compressor surge is simply defined as charge pressure pushing the compressor of a turbocharger the opposite way. so if that happens, then the turbo has to respool again. pressure will still remain, but it will work against the compressor. that is the whole point of a performance blow off valve. it's purpose is to relieve pressure so as to counter act the surge. yes pressure is lost, but by doing this, our friend kinetic energy keeps the compressor going the same way it was and as soon as you step on the gas it is still spinning the way that it should be going. it is a win win to have a blow off valve.
correct me if i am wrong
Christian
correct me if i am wrong
Christian
Originally Posted by rotarydelight
Maybe Its A External Wastegate?
#31
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Originally Posted by willub and company
I'm going to have to play devil's advocate here, you are contradicting yourself. compressor surge is simply defined as charge pressure pushing the compressor of a turbocharger the opposite way. so if that happens, then the turbo has to respool again. pressure will still remain, but it will work against the compressor. that is the whole point of a performance blow off valve. it's purpose is to relieve pressure so as to counter act the surge. yes pressure is lost, but by doing this, our friend kinetic energy keeps the compressor going the same way it was and as soon as you step on the gas it is still spinning the way that it should be going. it is a win win to have a blow off valve.
correct me if i am wrong
Christian
correct me if i am wrong
Christian
The surge isn't actually causing the compressor wheel to spin in the oposite direction, but instead the pressure waves are causing the wheel to slow down. So the turbo won't have to "respool" since it will still be spinning. If you check out the link Mahjik posted you'll see a chart that shows a car equiped with a BOV and one without. I hope this all makes sense and the chart helps a bit Most competition cars do not use any sort of BOV for the performance benefits, as stated many times.
-Dan
#32
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Compressor surge is hard on the thrust bearing mechanism because the pressure that the compressor is seeing is much greater than the pressure that the turbine is seeing, causing a thrust towards the compressor side.
Many OEM cars actually have good turbo size matching so that everytime the there is low load on the engine or the throttle plate is closed, it does not run the turbo in the surge part of the compressor map.
Running huge turbos like our GT42's on our 13B's is NOT a practical or good match, but it does yield great high end power. That being said, BOV's are very necessary when running large turbos, and that's why BOV's are open at idle.
Not running a BOV won't cause reverse spinning of the compressor wheel. It will slow the wheel down, but not like many people think would happen. The compressor wheel is not designed to spin when you put air reverse through the compressor outlet.
I think it is possible that not running a BOV would increase response, but I don't have any data that proves it one way or not, maybe someone else does. If this really bothers people, I can see what I can dig up.
Many OEM cars actually have good turbo size matching so that everytime the there is low load on the engine or the throttle plate is closed, it does not run the turbo in the surge part of the compressor map.
Running huge turbos like our GT42's on our 13B's is NOT a practical or good match, but it does yield great high end power. That being said, BOV's are very necessary when running large turbos, and that's why BOV's are open at idle.
Not running a BOV won't cause reverse spinning of the compressor wheel. It will slow the wheel down, but not like many people think would happen. The compressor wheel is not designed to spin when you put air reverse through the compressor outlet.
I think it is possible that not running a BOV would increase response, but I don't have any data that proves it one way or not, maybe someone else does. If this really bothers people, I can see what I can dig up.
Last edited by CarbonR1; 08-15-06 at 12:02 AM.
#33
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Originally Posted by CarbonR1
If this really bothers people, I can ask around at work.
#34
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Originally Posted by RE-Amemiya7
Just thought you guys would like to see some nice footage of the Stillway FD track car, as well as some other crazy fast cars. I have not seen this posted here yet, so if someone already has, my bad.
Actually the real reason why I posted this (besides sharing the vid) is to see if any of you can name that BOV on the AUTO SELECT Skyline (the yellow/carbon one) by its sound? The first time I heard it I almost crapped my pants, I have never heard one that sinister before! I cant seem to find any stats about the AUTO SELECT Skyline in English so I hope you guys can help.
Enjoy the vid!
Actually the real reason why I posted this (besides sharing the vid) is to see if any of you can name that BOV on the AUTO SELECT Skyline (the yellow/carbon one) by its sound? The first time I heard it I almost crapped my pants, I have never heard one that sinister before! I cant seem to find any stats about the AUTO SELECT Skyline in English so I hope you guys can help.
Enjoy the vid!
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Originally Posted by Fd3s4e
Thats because it's not just Auto select. I remeber seeing that GTR before and being labeled as "Powercraft" R34 or "Powershark" I think. As far as that silver R34 goes being "the high power tuned car in Japan!" LMAO @ THAT! 800hp is nothing to them! Look at signals R34 pushing over 1200 to the wheels! We have achieved over 1300 RWHP in supra's over in the states which leaves no doubt in my mind the Japs have gotten to over 1600+ hp in any of Jap's top contenders. I'm pretty sure those wanguners have gotten some rediclious power!
#37
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I really really don't believe this is true. That sounds EXACTLY like a GReddy Type S / Type R.
Originally Posted by Scrub
That BOV would be BOV less from the sound of it. So remove your BOV or just the vac source and you too can have your car sound like this.
Just be forwarned that if your car starts to sound like the stillway car, your turbo life expectancy will decline greatly. Unless your car is a straight track car, and you're sponsored by a turbo company I would not remove the pressure relief source from the intake tract at all.
-Dan
Just be forwarned that if your car starts to sound like the stillway car, your turbo life expectancy will decline greatly. Unless your car is a straight track car, and you're sponsored by a turbo company I would not remove the pressure relief source from the intake tract at all.
-Dan
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Originally Posted by CarbonR1
Running huge turbos like our GT42's on our 13B's is NOT a practical or good match, but it does yield great high end power. That being said, BOV's are very necessary when running large turbos, and that's why BOV's are open at idle.
Err..pretty sure an open BOV at idle would cause a mega-vacuum leak..
BOV's are closed at idle, and only open when your engine switches from boost to vacuum. Thus the reason for a vacuum line running to your BOV from a source of vacuum.
#39
2/4 wheel cornering fiend
Originally Posted by adrock3217
Err..pretty sure an open BOV at idle would cause a mega-vacuum leak..
BOV's are closed at idle, and only open when your engine switches from boost to vacuum.
BOV's are closed at idle, and only open when your engine switches from boost to vacuum.
Originally Posted by adrock3217
Thus the reason for a vacuum line running to your BOV from a source of vacuum.
#40
development
Originally Posted by adrock3217
I really really don't believe this is true. That sounds EXACTLY like a GReddy Type S / Type R.
Originally Posted by Kento
Nope. The BOV is actually venting at idle, because it allows air to bypass the turbo for smoother idle (so it doesn't have to draw air past the impeller). The idle fueling maps take this into account.
Right, so think about it: what is your intake tract producing at idle? It's certainly not producing any boost...
Right, so think about it: what is your intake tract producing at idle? It's certainly not producing any boost...
Kento - How exactly is air bypassing the turbo? Are you saying the engine is sucking air from the BOV to feed idle?
#41
2/4 wheel cornering fiend
Originally Posted by dubulup
My BOV isn't open at idle...and doesn't open until around 18in-hg
Kento - How exactly is air bypassing the turbo? Are you saying the engine is sucking air from the BOV to feed idle?
Kento - How exactly is air bypassing the turbo? Are you saying the engine is sucking air from the BOV to feed idle?
Yes, the engine uses it for partial idle air feed. Check how the stock "air bypass valve" (basically the OE blow-off valve) is hooked up. There's the big hose feeding into the valve from the Y-pipe (after the turbos) and then the exit side into the airbox. The actuator line is hooked up to a nipple on the UIM. When you start boosting, positive pressure in the actuator line shuts the valve. When you let off the throttle and the throttle plates shut, a vacuum is created in the UIM, which opens the BOV. However, there's vacuum created during idle as well, so the valve is open. The stock specs for the BOV are fully open at 9.2 inHg, which is far less vacuum than a good-running stock engine produces at idle.
EDIT: Sorry, made a mistake, the idle fueling maps on the FD don't take the air feed from the air bypass valve into effect, because the throttle plates are shut, and the throttle body controls air feed at idle. I was thinking of another application...
Last edited by Kento; 08-15-06 at 04:23 PM.
#42
development
^right, I think that is where the confusion was.
some cars will not run correctly if BOV (also called recirc valve) is vented to atmosphere...we all know this is not the case for FD's.
some cars will not run correctly if BOV (also called recirc valve) is vented to atmosphere...we all know this is not the case for FD's.
#43
Originally Posted by Kento
Nope. The BOV is actually venting at idle, because it allows air to bypass the turbo for smoother idle (so it doesn't have to draw air past the impeller).
~Ramy
PS: I find it fascinating that something as simple as a BOV is so poorly understood by most on the forum hehe.
#44
Originally Posted by dubulup
didn't see one in the engine bay...not that, that would be the end all debate here.
Sure sound's like it has one to me.
#45
2/4 wheel cornering fiend
Originally Posted by FDNewbie
Kento, so if it's venting at idle, it's actually allowing the turbine to slow down even more, correct? Which would cause lag (negligible or not, but some lag in the absolute sense) when attempting to make boost, correct? And this is in contrast to no BOV, so there's no venting at idle, so while the wheel slows down, it does so passively, and as such not as much? So response is faster when boost is desired? Or am I way off?
~Ramy
PS: I find it fascinating that something as simple as a BOV is so poorly understood by most on the forum hehe.
~Ramy
PS: I find it fascinating that something as simple as a BOV is so poorly understood by most on the forum hehe.
Without any BOV, I'd think the pressure waves that would result from backing off the throttle would play havoc with the compressor side, because a turbo depends on the airflow's centrifugal inertia to build pressure. However, I guess the response time when getting back on the throttle is worth it to those particular racecar applications.
#46
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Well, never thought my asking the question, "what BOV is it" would go in this direction. But, I'm glad to see that we have stumbled onto some rather interesting discussion! Any others with imput?
#47
Originally Posted by Kento
No, the turbo doesn't lose any spool speed from the BOV venting at idle because the exhaust energy is still spinning the exhaust turbine. Depending on the turbo setup, there will be some slight lag when you get back on the throttle, as it must pressurize the intake tract in order to build boost pressure again, but this is why the race vs. street use application must be taken into consideration with regards to turbo life vs. performance needs. And if the turbo setup is properly sized to the engine without requiring astronomical boost psi figures, lag time with a BOV is minimal anyway.
Without any BOV, I'd think the pressure waves that would result from backing off the throttle would play havoc with the compressor side, because a turbo depends on the airflow's centrifugal inertia to build pressure. However, I guess the response time when getting back on the throttle is worth it to those particular racecar applications.
Without any BOV, I'd think the pressure waves that would result from backing off the throttle would play havoc with the compressor side, because a turbo depends on the airflow's centrifugal inertia to build pressure. However, I guess the response time when getting back on the throttle is worth it to those particular racecar applications.
And what exactly is causing premature turbo life, now that we've established that spinning in reverse isn't true. Is it that it's spinning nonetheless w/o a BOV, or at least spinning faster at idle w/o a BOV? So just more wear and tear?
#48
2/4 wheel cornering fiend
Originally Posted by FDNewbie
Hmm...so the BOV is venting the intake tract, and repressurizing THAT is what may cause that lag (in the case of a huge turbo generating lots of boost)?
Originally Posted by FDNewbie
And what exactly is causing premature turbo life, now that we've established that spinning in reverse isn't true...So just more wear and tear?
Originally Posted by CarbonR1
Compressor surge is hard on the thrust bearing mechanism because the pressure that the compressor is seeing is much greater than the pressure that the turbine is seeing, causing a thrust towards the compressor side.
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Originally Posted by Scrub
I thought the car being referred to was the stillway Rx-7?
Uh . . . . . no. He clearly stated he was asking about the GT-R..
And to the BOV comment. I am positive that the BOV is NOT open at idle. Now, the only cars I have experience with this are the 87-91 RX-7 Turbos, and SRT-4's. But...if you put your hand on the BOV at idle, it doesn't change anything. This is of course for aftermarket, or atmospheric-vented stock BOV's...but this whole discussion was around BIG turbos, thus..you wouldn't be using a stock-setup BOV...