compressor surge fluttering, VIDEO inside!! :)
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From: Oxford UK
compressor surge fluttering, VIDEO inside!! :)
Hi all,
I've posted this video up in a few different threads already as it relates to a few of them! But I thought I'd add it up one last time with "video" in the title... because everyone loves videos! lol. I do appologise if you've already seen the link elsewhere, just ignore!
There are two things really...
1) The "wooshing" sound that's heard on the 3k warmup... it's pretty loud but i'm sure it's just the noise the intakes make sucking the air in at a high rate... I've had lots of cars in the past that hiss like mad with aftermarket induction kits, especially on cold startups! I'm pretty certain it's not a problem as the noise only started after I fitted the induction kit (apexi power) and I didn't touch anything else at that time but I thought I'd post the vid for others to look at!
2) The flutering sound at around 22 seconds... sounds like compressor surge?! Although there will be very little boost with no load surely...?! It only seems to flutter on a cold engine, and only with the HKS SSQV i've installed. No fluttering with standard BOV. The adjustment screw is all the way in, as others seem to run them. Is this likely to be a problem and should I just remove the ssqv for good? or is there a reason for it to be doing this when cold...
maybe it's all fine and I don't need to worry
in an ideal world...!!
http://www.youtube.com/watch?v=IOn8xBHb0Zw
I've posted this video up in a few different threads already as it relates to a few of them! But I thought I'd add it up one last time with "video" in the title... because everyone loves videos! lol. I do appologise if you've already seen the link elsewhere, just ignore!
There are two things really...
1) The "wooshing" sound that's heard on the 3k warmup... it's pretty loud but i'm sure it's just the noise the intakes make sucking the air in at a high rate... I've had lots of cars in the past that hiss like mad with aftermarket induction kits, especially on cold startups! I'm pretty certain it's not a problem as the noise only started after I fitted the induction kit (apexi power) and I didn't touch anything else at that time but I thought I'd post the vid for others to look at!
2) The flutering sound at around 22 seconds... sounds like compressor surge?! Although there will be very little boost with no load surely...?! It only seems to flutter on a cold engine, and only with the HKS SSQV i've installed. No fluttering with standard BOV. The adjustment screw is all the way in, as others seem to run them. Is this likely to be a problem and should I just remove the ssqv for good? or is there a reason for it to be doing this when cold...
maybe it's all fine and I don't need to worry
in an ideal world...!!http://www.youtube.com/watch?v=IOn8xBHb0Zw
Thread Starter
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Joined: May 2008
Posts: 56
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From: Oxford UK
Are you refering to the "wooshing/hissing" noise? or the flutterig noise... I'm sure my standard bov didn't cause a fluttering noise from the intakes! One way to find out I suppose...! I think the fluttering is coming from the primary turbo intake though, so sounds like compressor surge still? Or am I just trying to convince myself here?!!
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From: Oxford UK
Just an update:
the standard bov vents a lot of air when you hold the revs at say 2500rpm. When you blip the throttle or drive on boost however the valve does not vent until you come off the throttle, like it should.
This air vented continuously under a constant rev (but no load) situation would explain why the HKS valve causes surge as it does not vent the air under such conditions and the built up boost obviously has no where else to go but back to the turbo! Surge...
Make sense?! It does to me!!
Having said all that, I can't see how any hks valve would work without causing this surge under no load conditions. Unless mine is just faulty, possibly leaking...
the standard bov vents a lot of air when you hold the revs at say 2500rpm. When you blip the throttle or drive on boost however the valve does not vent until you come off the throttle, like it should.
This air vented continuously under a constant rev (but no load) situation would explain why the HKS valve causes surge as it does not vent the air under such conditions and the built up boost obviously has no where else to go but back to the turbo! Surge...
Make sense?! It does to me!!
Having said all that, I can't see how any hks valve would work without causing this surge under no load conditions. Unless mine is just faulty, possibly leaking...
RX7 lover
Joined: Jun 2005
Posts: 1,160
Likes: 3
From: UK
I havent watched the video BUT!
I have the same BOV as you on my car. Adjust the adjustment screw on the SSQV out about half an inch, and you will no longer get this flutter.
A bov does not need to vent any air at part load. The engine should be using all the air provided to it - the turbos will provide no boost as the volume of exhaust gas will not be high enough to sufficiently spin them.
The SSQV works by PULLING a plunger backwards allowing air out, rather than with a stock dump valve (or any other dump valve pretty much) its the other way around. A good analogy is that a standard dump valve works like taking the lid off a bottle (i.e the gas vented is trying to push the valve open) and with an SSQV its like having a stop inside the neck of the bottle that has to be pulled into the bottle to allow gas out (i.e the gas vented is trying to push the valve CLOSED)
This makes for a much less leaky BOV and means air will never be vented through the BOV except when theres a lot of vacuum on it.
The adjustment screw adjusts the tension on the spring keeping the valve closed, effectively changing the amount of vacuum you need for the BOV to open. Screw it all the way in, you need lots of vacuum to open the valve. Screw it all the way out and youll need less vacuum (but it will COME out completely so be careful!)
Thus with the screw screwed all the way in and the car at part throttle (i.e turbos spinning but no boost being created) when you lift off the BOV will not open, so you get a little compressor stall (which is what that noise is)
When you really floor it the pressure differential trying to open the valve is greater so it opens and the boost is vented.
hope this helps!
I have the same BOV as you on my car. Adjust the adjustment screw on the SSQV out about half an inch, and you will no longer get this flutter.
A bov does not need to vent any air at part load. The engine should be using all the air provided to it - the turbos will provide no boost as the volume of exhaust gas will not be high enough to sufficiently spin them.
The SSQV works by PULLING a plunger backwards allowing air out, rather than with a stock dump valve (or any other dump valve pretty much) its the other way around. A good analogy is that a standard dump valve works like taking the lid off a bottle (i.e the gas vented is trying to push the valve open) and with an SSQV its like having a stop inside the neck of the bottle that has to be pulled into the bottle to allow gas out (i.e the gas vented is trying to push the valve CLOSED)
This makes for a much less leaky BOV and means air will never be vented through the BOV except when theres a lot of vacuum on it.
The adjustment screw adjusts the tension on the spring keeping the valve closed, effectively changing the amount of vacuum you need for the BOV to open. Screw it all the way in, you need lots of vacuum to open the valve. Screw it all the way out and youll need less vacuum (but it will COME out completely so be careful!)
Thus with the screw screwed all the way in and the car at part throttle (i.e turbos spinning but no boost being created) when you lift off the BOV will not open, so you get a little compressor stall (which is what that noise is)
When you really floor it the pressure differential trying to open the valve is greater so it opens and the boost is vented.
hope this helps!
RX7 lover
Joined: Jun 2005
Posts: 1,160
Likes: 3
From: UK
P.s that flutter sounds cool, would be great to start in a car park full of people lol. Keep it!
FYI its how i run mine. but i have no AWS Airpump or anything like that so i only get the noise when im careful with my foot.
FYI its how i run mine. but i have no AWS Airpump or anything like that so i only get the noise when im careful with my foot.
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Thread Starter
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Joined: May 2008
Posts: 56
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From: Oxford UK
It was all very helpful! Just a little confused on one thing though...
How are you saying you run yours? screw fully in, or an inch out?! And does yours make the flutter?! lol, I was a little confused on those two points! I'll try mine an inch out and see how it goes! It's been on and off the car about 4 times every day for the past week trying to understand all this! Just want to make sure nothing's going to be damaged...
It doesn't appear to be venting properly (loudly...) at higher revs... although I have been having some secondary turbo problems!! All in all, I've been a little weary about keeping it on the car without seeking further advice!
Thanks again
