Post your Synapse DV config and results
The only thing major I changed was tightening the wga.This is probably one of the more brilliant bits of feedback in a while. My comments will ONLY apply to those that are getting "flutter" on boost, on throttle. It is really quite difficult to tell the difference between real compressor surge (bouncing off the surge line) and a wastegate flutter (wastegate bouncing open) on an OEM car with a re-circulated WG discharge. We can tell pretty easily when an EWG is used because we can just hold it shut with pressure and at that point it can't be anything else.
In all of our testing with on-boost flutter/surge, we outfitted a DV/SB with a lift position sensor or eliminated the DV/SB from the system. If the DV/SB was eliminated, we found that the problem was still there, so it wasn't anything the DV/SB could fix or have anything to do with. With the lift sensor, the DV/SB would never even show 0.1 mm of lift in any condition under boost. And as a side note, we conduct testing all the time to purposely leak the DV to control compressor behavior and not once has the noise or lift signature ever sounded or looked like flutter. If the DV is leaking, or controlling boost pressure like a wastegate, it is a very linear dump of air. So, the only thing that could make that fluttering sound is either the wastegate or compressor surge.
As I've said, it is hard to tell the difference between the two since both scenarios will make boost pressure oscillate. Since the DV/SB doesn't leak charge air, what we have seen is that swapping it out for a leaky unit will increase the mass flow in the exhaust. If the wastegate isn't pre-loaded enough when swapping to the DV/SB then what you will get is "wastegate flutter." The funny thing is that with the Subaru community, Wastegate Flutter is a given and those guys expect it. But no one seems to have a solution for it.
It all makes sense! One of the first things you need to try is to tighten up the WG actuator arm just enough to add pre-load, but not so much that it raises your boost pressure. There is so much variation from car to car with how many turns it was out of the factory, how stretchy the diaphragm is in the WGA, and how strong is your spring, etc that it makes sense that it would happen on some cars and not on others.
Again, this is only for on-throttle flutter.
Evolving Member
Joined: Mar 2009
Posts: 107
Likes: 0
From: Ohio
Did your boost go up when you did this adjustment?
This is probably one of the more brilliant bits of feedback in a while. My comments will ONLY apply to those that are getting "flutter" on boost, on throttle. It is really quite difficult to tell the difference between real compressor surge (bouncing off the surge line) and a wastegate flutter (wastegate bouncing open) on an OEM car with a re-circulated WG discharge. We can tell pretty easily when an EWG is used because we can just hold it shut with pressure and at that point it can't be anything else.
In all of our testing with on-boost flutter/surge, we outfitted a DV/SB with a lift position sensor or eliminated the DV/SB from the system. If the DV/SB was eliminated, we found that the problem was still there, so it wasn't anything the DV/SB could fix or have anything to do with. With the lift sensor, the DV/SB would never even show 0.1 mm of lift in any condition under boost. And as a side note, we conduct testing all the time to purposely leak the DV to control compressor behavior and not once has the noise or lift signature ever sounded or looked like flutter. If the DV is leaking, or controlling boost pressure like a wastegate, it is a very linear dump of air. So, the only thing that could make that fluttering sound is either the wastegate or compressor surge.
As I've said, it is hard to tell the difference between the two since both scenarios will make boost pressure oscillate. Since the DV/SB doesn't leak charge air, what we have seen is that swapping it out for a leaky unit will increase the mass flow in the exhaust. If the wastegate isn't pre-loaded enough when swapping to the DV/SB then what you will get is "wastegate flutter." The funny thing is that with the Subaru community, Wastegate Flutter is a given and those guys expect it. But no one seems to have a solution for it.
It all makes sense! One of the first things you need to try is to tighten up the WG actuator arm just enough to add pre-load, but not so much that it raises your boost pressure. There is so much variation from car to car with how many turns it was out of the factory, how stretchy the diaphragm is in the WGA, and how strong is your spring, etc that it makes sense that it would happen on some cars and not on others.
Again, this is only for on-throttle flutter.
This is probably one of the more brilliant bits of feedback in a while. My comments will ONLY apply to those that are getting "flutter" on boost, on throttle. It is really quite difficult to tell the difference between real compressor surge (bouncing off the surge line) and a wastegate flutter (wastegate bouncing open) on an OEM car with a re-circulated WG discharge. We can tell pretty easily when an EWG is used because we can just hold it shut with pressure and at that point it can't be anything else.
In all of our testing with on-boost flutter/surge, we outfitted a DV/SB with a lift position sensor or eliminated the DV/SB from the system. If the DV/SB was eliminated, we found that the problem was still there, so it wasn't anything the DV/SB could fix or have anything to do with. With the lift sensor, the DV/SB would never even show 0.1 mm of lift in any condition under boost. And as a side note, we conduct testing all the time to purposely leak the DV to control compressor behavior and not once has the noise or lift signature ever sounded or looked like flutter. If the DV is leaking, or controlling boost pressure like a wastegate, it is a very linear dump of air. So, the only thing that could make that fluttering sound is either the wastegate or compressor surge.
As I've said, it is hard to tell the difference between the two since both scenarios will make boost pressure oscillate. Since the DV/SB doesn't leak charge air, what we have seen is that swapping it out for a leaky unit will increase the mass flow in the exhaust. If the wastegate isn't pre-loaded enough when swapping to the DV/SB then what you will get is "wastegate flutter." The funny thing is that with the Subaru community, Wastegate Flutter is a given and those guys expect it. But no one seems to have a solution for it.
It all makes sense! One of the first things you need to try is to tighten up the WG actuator arm just enough to add pre-load, but not so much that it raises your boost pressure. There is so much variation from car to car with how many turns it was out of the factory, how stretchy the diaphragm is in the WGA, and how strong is your spring, etc that it makes sense that it would happen on some cars and not on others.
Again, this is only for on-throttle flutter.
Weren't you working on a new spring for the DV that had less spring rate? I dont necessarily like running a cut spring because it does not seat nice and flat so i dont know if it will cause accelerated wear on the valve. Cutting the spring almost eliminated my flutter problem (and it was pretty stinkin bad).
Evolving Member
Joined: Apr 2007
Posts: 185
Likes: 0
From: Coronado, CA
I PM'd Aby a few days ago asking about the spring and what I need to do to install it. Aby said to just drive up and I'll do it for you. So I did. Real nice guy!
I bought the car a few months ago and it's my first turbo vehicle. I really enjoyed driving the car but was beginning to think bucking and flutter was just part of the deal.
Driving impressions: Part throttle lift flutter is gone. The violent blow off is now a nice, smooth, controlled whoosh. Bottom line is a little spring has me more excited about driving my car and ain't that what its all about it here?
I bought the car a few months ago and it's my first turbo vehicle. I really enjoyed driving the car but was beginning to think bucking and flutter was just part of the deal.
Driving impressions: Part throttle lift flutter is gone. The violent blow off is now a nice, smooth, controlled whoosh. Bottom line is a little spring has me more excited about driving my car and ain't that what its all about it here?
Thinking I need this spring as I previously stated I thought that it had gone away after tightning the wga it hasn't only less now. I believe now that a slightly less spring would take this bov from being near perfect to perfect.Aby I need one 
^ I will get 1 shipped out tomorrow.
BTW, this spring is only for the latest synapse bov, that is small.
NOT for the large synapse bov.
I recently had someone order 1 & after speaking to him, i learned that the unit he had was the larger bov.
BTW, this spring is only for the latest synapse bov, that is small.
NOT for the large synapse bov.
I recently had someone order 1 & after speaking to him, i learned that the unit he had was the larger bov.
I've just fitted one of these to my Airtrek, only a 5 minute drive so far. A question thou, the hoses and fittings have a heat warning on them, no issue as I'm not using them, but how about the DV itself? The reason I ask is that my DV is mounted about 40mm away from the heat shield of my exhaust manifold. My intercooler piping runs over my intake pipe instead of under due to the size and shape of my auto gearbox. I actually run a hose with a 90 degree bend off the intercooler piping and the DV connects directly into the intake pipe. I've tried all sorts of ways to try and mount the DV directly off the intercooler piping away from the manifold, but can't get anything to work without having to chop up my piping and start from scratch.
Initial setting is Push with B and I have flutter in lower rpm lift offs.
Initial setting is Push with B and I have flutter in lower rpm lift offs.
I have the Synapse DV on my EVO 8, and I'm now very satisfied with it. But I wasn't so happy when it was first installed. The car bucked and made noises when being shifted in any gear, and was even worse when under high boost. I then followed the recommendations most often made in this thread...Port B only, pull mode, no pre-lode. That helped a lot (Thanks, every one, for your posts). But, it still wasn't right. Suspecting that maybe the DV was leaking, or that I had some other boost leak, I leak tested the boost system to 30+ psi. I found and fixed some minor leaks, but not in the Synapse DV. It never leaked at any time (Good job, Synapse). But, still no better.
Mostly out of desperation, I attached a vacuum source to the plastic quick-connect line that supplied vacuum to the DV, to see if it was operating properly. Big surprise...I couldn't get even 2 psi (vacuum) to the DV. The fittings on the DV were leaking big time. I checked the factory supplied Y fitting which I had already removed, and it leaked just as bad. I re-installed the plastic lines after making certain that they were cut perfectly square. No change. I called Synapse, and advised them of the problem I was having. They were very helpful, and said that they would ship me new fittings free of charge. They also said that they would send me two metal fittings with hose nipples so that I would have the option of using a rubber vacuum hose. (I believe that the hose nipples are now included in the install kit). I ended up using them with a rubber vacuum line. That solved that problem. Good customer service from Synapse
. I want to emphasize that just because the DV is holding boost (over 30 psi in my case) that doesn't mean that it is opening / closing properly. I realize that some owners have had no issues with the quick-connect lines, but I am also aware that others have.
At this point, the Synapse DV was working much, much better. (Maybe because it was actually opening properly). But...I can't qualify this with data...the car just didn't feel quite right. I've had this Evo for seven years, and it wasn't running the way I knew it should.
The final change that made the Synapse DV perfect (for my Evo at least) was the softer spring from Aby @ Mil.Spec. I installed it (with no preload) in about ten minutes. I can't think of any way it could be better. Thanks, Aby.
As I said at the start, I'm very satisfied with the Synapse DV. I started out not so happy with it, but now I wouldn't have anything else.
Combined with a super-tune and mucho mods by everyone at CBRD, my Evo has never run so good. (I don't want to say too much, or Chad will start charging more!)
I hope this might help some evolutionm members. You've sure helped me over the last seven years. Thank you all.
Mostly out of desperation, I attached a vacuum source to the plastic quick-connect line that supplied vacuum to the DV, to see if it was operating properly. Big surprise...I couldn't get even 2 psi (vacuum) to the DV. The fittings on the DV were leaking big time. I checked the factory supplied Y fitting which I had already removed, and it leaked just as bad. I re-installed the plastic lines after making certain that they were cut perfectly square. No change. I called Synapse, and advised them of the problem I was having. They were very helpful, and said that they would ship me new fittings free of charge. They also said that they would send me two metal fittings with hose nipples so that I would have the option of using a rubber vacuum hose. (I believe that the hose nipples are now included in the install kit). I ended up using them with a rubber vacuum line. That solved that problem. Good customer service from Synapse
. I want to emphasize that just because the DV is holding boost (over 30 psi in my case) that doesn't mean that it is opening / closing properly. I realize that some owners have had no issues with the quick-connect lines, but I am also aware that others have. At this point, the Synapse DV was working much, much better. (Maybe because it was actually opening properly
). But...I can't qualify this with data...the car just didn't feel quite right. I've had this Evo for seven years, and it wasn't running the way I knew it should.The final change that made the Synapse DV perfect (for my Evo at least) was the softer spring from Aby @ Mil.Spec. I installed it (with no preload) in about ten minutes. I can't think of any way it could be better. Thanks, Aby
. As I said at the start, I'm very satisfied with the Synapse DV. I started out not so happy with it, but now I wouldn't have anything else.
Combined with a super-tune and mucho mods by everyone at CBRD, my Evo has never run so good. (I don't want to say too much, or Chad will start charging more!
)I hope this might help some evolutionm members. You've sure helped me over the last seven years. Thank you all.
I've also been running the spring offered by Aby at Mil.Spec for about 2 weeks now. The best configuration I've run is push, port b, one turn preload. It's been absolutely awesome. Low boost throttle lift has no bucking and WOT still holds full boost (26psi in my case). I love this spring. Thanks Aby. 
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Joined: Jul 2011
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From: Clinton, NJ - Myrtle Beach, SC
Aby, you mind shooting me a PM for one of the springs including shipping to 08809? Thanks man!
is low rpm partial throttle flutter bad? my crushed IX DV always did it but the synapse does it a littttle bit more, but driveability is definitely better than the stock one, and it sounds a little nicer too :]
installed the synapse dv in push mode, zero preload, a port conntected, b port open
installed the synapse dv in push mode, zero preload, a port conntected, b port open