Help, my twins sound like a dremmel
#26
What's your point ?
Join Date: Feb 2001
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Originally Posted by Barban
ENGLISH ************ DO YOU SPEAK IT?
When you tighten the screw it forces the same air through a tiny space. The air cant get out. It makes a loud noise. It breaks your turbos. .
You loosen the screw. It lessens the restriction. It makes less noise. Your turbos live!
You are sharp like a bag of hair, son. Go splash water on your face. Do anything but ******* post again. Read. Read a lot. Read for 4 years then start posting. GO AWAY.
When you tighten the screw it forces the same air through a tiny space. The air cant get out. It makes a loud noise. It breaks your turbos. .
You loosen the screw. It lessens the restriction. It makes less noise. Your turbos live!
You are sharp like a bag of hair, son. Go splash water on your face. Do anything but ******* post again. Read. Read a lot. Read for 4 years then start posting. GO AWAY.
Actually the screw your tightening up increases the spring pressure against the piston that the vacuum pulls against, it doesn't close up the oriface it just requies more vacuum to open it and closes the port quicker as the spring pressure over comes the vacuum, this is what gives you a sharper (louderblast of air) screw turned in as opposed to a softer longer discharge (screw out) aftermarket BOV manufacturers have other gimmicks such as heavier springs and port inserts to achieve the sound and boost pressure needs of the buyer.
#30
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iTrader: (7)
Originally Posted by Barban
Air coming through your turbo is exactly what breaks turbos. The air came out of your turbo because your BOV was all the way closed and the air had nowhere else to run to. When you loosened your BOV the BOV did what it was supposed to do. Vent air. BOV's make noise when they vent air. So youre right a fully tightened BOV would not make any noise. It would eat your turbo. A highly tightened(but not closed) BOV would make the most noise possible and also.....you got it! EAT YOUR TURBOS! Its called backspin or bounce. Its when the air pressure is so high that the metal turbo blades actually bounce off the air and then spin backwards to release the pressure built up in front of the turbo. Its a bad thing. They go from spinning full speed in one direction to full speed in reverse in about .0000000000001 seconds. Now metal is real strong but when things are spinning at sat 125,000 rpms and then go to -125,000rpms(a change of 250,000rpms) in the blink of an eye it snaps the turbo shaft in half instantly.
I'm afraid I don't have facts to add about how BOV settings affect compressor surge, and how this *might* cause the turbos extra stress. However, if the turbo is rubbing on the housing to make the noise, they need replaced. Simple as that.
Dave
#32
Rx7 Wagon
iTrader: (16)
Originally Posted by dgeesaman
The compressors never spin in reverse, or even close to zero. The airflow always flows into the engine, and the exhaust always flows out.
Dave
Dave
#33
Rx7 Wagon
iTrader: (16)
backspin is a reality
The blow-off valve is essential to all turbocharged vehicles. The purpose of these Blitz dual drive blow-off valves is to relieve compressor surge without reducing compressor speed. They control boost pressure that is built up by the turbo and vent it into the atmosphere when the car is not under load (in between shifts).This prevents pressure from backing up into the compressor housing, causing the turbo impeller blade to rapidly stop or, even worse, to spin backwards (compressor surge or backspin). Doing so can be potentially destructive to the turbine wheel and shaft. Repeated stress over time can cause eminent damage to the turbo charger and eventually lead to turbo failure. The blow-off valves are actuated by pressure changes only, ensuring quick valve responses and complete closures at idle. Blitz's dual drive blow-off valves not only improve performance and response, but they also increase the life of the turbocharger.
from:http://store.summitracing.com/defaul...5&autoview=sku
The blow-off valve is essential to all turbocharged vehicles. The purpose of these Blitz dual drive blow-off valves is to relieve compressor surge without reducing compressor speed. They control boost pressure that is built up by the turbo and vent it into the atmosphere when the car is not under load (in between shifts).This prevents pressure from backing up into the compressor housing, causing the turbo impeller blade to rapidly stop or, even worse, to spin backwards (compressor surge or backspin). Doing so can be potentially destructive to the turbine wheel and shaft. Repeated stress over time can cause eminent damage to the turbo charger and eventually lead to turbo failure. The blow-off valves are actuated by pressure changes only, ensuring quick valve responses and complete closures at idle. Blitz's dual drive blow-off valves not only improve performance and response, but they also increase the life of the turbocharger.
from:http://store.summitracing.com/defaul...5&autoview=sku
#34
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iTrader: (7)
Originally Posted by Barban
Im going to disagree. In a closed BOV, closed throttle, high boost situation the exhaust pressure on the turbos would be less than the pressure exerted by the compressed air in front of the turbos creating this bounce that I spoke of. I know LITTLE about turbochargers. But it seems to me that even in some remote circumstance it would be possible to spin the turbos in reverse in a running engine condition. I mainly believe this because with the throttle closed to idle there would be lots of pressure in front at boost and relatively little pressure behind the turbos at idle. Wether or not this is possible simply depends on how much boost youre pushing and how much exhaust youre putting out. I think, the larger the turbo the more real this possiblity becomes.
In theory this is possible. In practice, I think you'd have to set the BOV to such a low vacuum that it wouldn't open at all, and not vent air for at least a second or two. (Remember, it takes about a second to spool the turbos, so stopping them would be similar).
I was reading about some of these aftermarket BOVs, and it's not clear to me how crazy (wrong) you have to adjust them to cause this problem. But it does appear it's possible. I suspect that bearing damage is more likely with a ball-bearing turbo, since high rpms will quickly kill a ball bearing. Sleeve bearings in can carry greater load at high rpm, but it's not clear to me whether heat becomes a problem instead.
I sure would make an effort to get that BOV properly adjusted. It's pretty sad when what amounts to a noisemaker may have killed your turbos.
Dave
#35
Moderator
iTrader: (7)
I continued to research it and found similar info. When I was writing that statement, I was mistakenly picturing the stock setup. Aftermarket BOVs give you more adjustments that give you opportunity to F things up.
I think you're right - if you really have your BOV adjusted wrong, you have the elements necessary to create a bad compressor surge instead of vent it like it's designed. It seems like it would need to be a pretty extreme set of circumstances, but it's possible.
Dave
I think you're right - if you really have your BOV adjusted wrong, you have the elements necessary to create a bad compressor surge instead of vent it like it's designed. It seems like it would need to be a pretty extreme set of circumstances, but it's possible.
Dave
Last edited by dgeesaman; 03-28-06 at 06:26 PM.
#36
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Read this about eliminating BOV, a tuner specialist from Australia eliminated all his BOV on all the FD he works on, and explains it pretty well. Look under Rice Racing post
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/about-eliminating-stock-bov-495277/
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/about-eliminating-stock-bov-495277/
#37
Do a barrel roll!
iTrader: (4)
Originally Posted by Barban
ENGLISH ************ DO YOU SPEAK IT?
When you tighten the screw it forces the same air through a tiny space. The air cant get out. It makes a loud noise. It breaks your turbos. .
You loosen the screw. It lessens the restriction. It makes less noise. Your turbos live!
You are sharp like a bag of hair, son. Go splash water on your face. Do anything but ******* post again. Read. Read a lot. Read for 4 years then start posting. GO AWAY.
When you tighten the screw it forces the same air through a tiny space. The air cant get out. It makes a loud noise. It breaks your turbos. .
You loosen the screw. It lessens the restriction. It makes less noise. Your turbos live!
You are sharp like a bag of hair, son. Go splash water on your face. Do anything but ******* post again. Read. Read a lot. Read for 4 years then start posting. GO AWAY.
Real mature. If you feel the need to post like this go talk to the kiddies in the lounge, this isnt the place for it. If you can't make a post without calling someone names and swearing, then dont post at all. You aren't helping anyone by doing so.
I dont really want to get into this whole discussion, but I really think you (not just you presonally, alot of people) need to do more research into the necessity of BOVs and what alot of racing teams have experimented with in the role they play with controlling compressor surge, or lack there-of. I think you will really be suprised in what you find.
Last edited by Rxmfn7; 03-28-06 at 06:51 PM.
#39
Rx7 Wagon
iTrader: (16)
If its too tight you put undue stress on your turbos or possibly even bounce them back. If its too lose you lose boost response. Please send me to a place to learn. I yearn for the knowledge of this clubs senior members such as yourself. And Ive been researching this periodically all day. As I do not have an adjustable BOV Im not intensely concerned with these adjustments but may be in the future. But the basics seem very simple and fundamental to me. Its the methodical bleeding of air to best maintain boost and save your turbo at the same time. You find the line in the sand like any other tuning.
Youre absolutely sarcasticly right. I was a big jerk and Ive apologised here and privately to streetRX7. In explanation of my jackassery: I posted something correct. I was told I was wrong. I flipped out. I apologise again. I normally dont get so heated over nothing and in the end it turns out streetRX7 was just as right as I was I simply didnt understand what he was saying.
Youre absolutely sarcasticly right. I was a big jerk and Ive apologised here and privately to streetRX7. In explanation of my jackassery: I posted something correct. I was told I was wrong. I flipped out. I apologise again. I normally dont get so heated over nothing and in the end it turns out streetRX7 was just as right as I was I simply didnt understand what he was saying.
#40
Rx7 Wagon
iTrader: (16)
Originally Posted by RotorJoe
So does that mean compressor surge is not as prevalent as everybody states? and we have all been dooped into buying rice?
This is very interesting.
This is very interesting.
#41
Hooray For Boobies!!!
/\ Did you read the link silverflash2 posted?
From what I gathered in RiceRacings posts, you don't need one. Did I miss read something?
I get what he is saying about having to build up the boost pressure again due to the BOV venting it all but I thought compressor surge would kill you turbo if you didn't have one. I don't understand the parts where he explains why you won't need one.
Thanks
Joe
From what I gathered in RiceRacings posts, you don't need one. Did I miss read something?
I get what he is saying about having to build up the boost pressure again due to the BOV venting it all but I thought compressor surge would kill you turbo if you didn't have one. I don't understand the parts where he explains why you won't need one.
Thanks
Joe
#42
Rx7 Wagon
iTrader: (16)
He may well be right but I dont buy a word of it. He talk about turbos before BOV's and how he "single handedly" proved that BOVs are bunk. Im gonna go research turbos pre BOV but the physics of the turbocharger say that you cant do that without stressing it out. maybe he uses super strong turbos? Ima go look into it but like I said I dont believe a word of it...yet
Last edited by Narfle; 03-28-06 at 07:25 PM.
#43
Do a barrel roll!
iTrader: (4)
Read this thread also:
https://www.rx7club.com/showthread.p...ght=blow+valve
Pretty good info and personal experiences there. Im not saying one isnt necessary at all or doesnt/cant serve a purpose, but I do think people place alot more concern than is needed on a BOV.
https://www.rx7club.com/showthread.p...ght=blow+valve
Pretty good info and personal experiences there. Im not saying one isnt necessary at all or doesnt/cant serve a purpose, but I do think people place alot more concern than is needed on a BOV.
#44
Rx7 Wagon
iTrader: (16)
Theoretically speaking, If you drew your pressure reading from between the compressor and the throttle body your wastegate would prevent the turbo from receiving and extra charge from the exhaust gases in an off throttle situation. Thats what ive gathered so far.
So, now there nothing pushing the compressor which is still spinning like a demon. And the wastegate is open so no gas is pushing it from behind. So when that wheel keeps trying to push air into the same chamber thats already full its still going to bounce. That wheel still has a bunch of momentum and its still pushing air where it wont fit. The turbo is only more likely to backspin with no exhaust pressure on it. So yeah. The surge is gone. But the bounce is still an issue.
And, that wouldnt be an obvious problem because you dont take any data on your turbo's rpms so you wouldnt even know. These race cars he references that run 36psi up pikes peak with no BOV are race cars. Theyre rebuilt every race and the turbos are not run of the mill units I assure you. All they have to do is survive 15 minutes and theyre done and probably dont race again. The turbochargers before BOV's he talks about broke down more than we do. Early turbocharger technology sucked. Hence the advent of things like THE BOV!
This flutter that you hear in this situation. The one that is blames on the wastegate opening and closing and not the turbo fluttering. Well its half right. Every time the turbo pushes boost into the closed chamber over your desired level the wastegate opens and the turbo bounces off. The boost leaks. The wastegate closes. The turbo bounces the other way. The boost builds up with no where to go. repeat process.
The last two paragraphs are conjecture. Im not a race mechanic and I dont design Turbos. I am real good at physics though. And thats the only way I could understand it happening. When a turbo wheel with only momentum behind it strikes a wall of air it will compress the air and bounce off(think air ride suspension).
Im keeping my BOV and my HUMBLE suggestion is that you do too.
So, now there nothing pushing the compressor which is still spinning like a demon. And the wastegate is open so no gas is pushing it from behind. So when that wheel keeps trying to push air into the same chamber thats already full its still going to bounce. That wheel still has a bunch of momentum and its still pushing air where it wont fit. The turbo is only more likely to backspin with no exhaust pressure on it. So yeah. The surge is gone. But the bounce is still an issue.
And, that wouldnt be an obvious problem because you dont take any data on your turbo's rpms so you wouldnt even know. These race cars he references that run 36psi up pikes peak with no BOV are race cars. Theyre rebuilt every race and the turbos are not run of the mill units I assure you. All they have to do is survive 15 minutes and theyre done and probably dont race again. The turbochargers before BOV's he talks about broke down more than we do. Early turbocharger technology sucked. Hence the advent of things like THE BOV!
This flutter that you hear in this situation. The one that is blames on the wastegate opening and closing and not the turbo fluttering. Well its half right. Every time the turbo pushes boost into the closed chamber over your desired level the wastegate opens and the turbo bounces off. The boost leaks. The wastegate closes. The turbo bounces the other way. The boost builds up with no where to go. repeat process.
The last two paragraphs are conjecture. Im not a race mechanic and I dont design Turbos. I am real good at physics though. And thats the only way I could understand it happening. When a turbo wheel with only momentum behind it strikes a wall of air it will compress the air and bounce off(think air ride suspension).
Im keeping my BOV and my HUMBLE suggestion is that you do too.
Last edited by Narfle; 03-28-06 at 07:56 PM.
#45
Damn I broke his neck!
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ok guys yeah i tightened the screw almost all the way which means when it was letting the pressure out, it was so tight that it was not able to let all of it out. turbo prolly back spooled and bam. it had very little shaft play before. turbos have 100k on them so its just about that time. they were boosting perfectly before, about 12-14 psi but now im lucky if i get 5-7. Stupid me. So now im in the thinking process of either getting me a nice set of bnr twins, some 99 twins, a nice single (nothing crazy, maybe a 60-1) or just parking the 7 and getting me a lil beater hatch civic or something. what do you guys think.
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