The building block

Rich · Postby **Rich** » Wed Nov 12, 2008 9:14

Serious flutter means more air to blow off? Not sure though. Maybe due to more sound from the inlet pipe?

firestoned · Postby **firestoned** » Wed Nov 12, 2008 9:14

I am worried it might be compressor surge. After some research, compressor surge happens during acceleration, not after letting off the gas. Compressor surge is when the bov isnt working, it tries pushing the air back on the impeller blades of the turbo, causing it to be bounced back and forth between the bov and the turbo, which ISNT good.. The sound still scares me, although it isnt as bad as it was originally.

I removed the spring and piston from the bov to oil them it last week, maybe the spring was too tight, and needed to adjust again... Ill see tomorrow, I dont know, it sounds pretty damn good, Im thinking of capping off the vta on the Turbosmart

bobopud · Postby **bobopud** » Wed Nov 12, 2008 9:14

So, you are getting a flutter during acceleration?

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

bobopud wrote:So, you are getting a flutter during acceleration?

no, Im only getting flutter when relieving pressure. I wonder if its always happend, and the longer intercooler pipes are making it echo?? I still cant determine if its compressor surge or not.

Ive contacted Jordan regarding the issue, trying to get his insight on the topic. I might be looking into getting the Synapse BOV which eliminates compressor surge by design

SpeedRacer · Postby **SpeedRacer** » Thu Nov 13, 2008 9:14

dont do synapse come on seriously? yuck.

Flutter is normal take a video and post it. Mine under low boost sounds like an HKS almost. If anything test a diff BOV. You make things so darn difficult for yourself. I mean if you wanna throw away money send me some...

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

From what I am reading, this is what I gather;

Fluttering is hard to distinguish between compressor surge, as they sound the same..but wait, others say compressor surge and fluttering ARE the same. And yet, some say compressor surge ONLY happens when building boost. Search youtube for compressor surge, and youll see hundreds of videos, these 2 have me confused..

This one says "true compressor surge"

[ame="http://www.youtube.com/watch?v=nCj6Spwl1CU"]YouTube - True Compressor Surge[/ame]

This one, along with hundreds others, says this is compressor surge

[ame="http://www.youtube.com/watch?v=LZUbo_mNDZM"]YouTube - SR20DET Compressor Surge[/ame]

My car sounds like the bottom video, just as long, and just as loud...thats HKS times 10.

Just4fun · Postby **Just4fun** » Thu Nov 13, 2008 9:14

If your car is like the bottom video and not experiencing this under load then there is a problem with the BOV opening correctly.

Another thought on this may be to check the connections along the discharge line from the compressor to the intake. It sounds like the closing of the throttle blade could be creating enough pressure to allow a leak somewhere along the line. I had this problem with a supercharged Mustang running a front mount intercooler.

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

Here is a video, crappy from blackberry, but you get the idea...
The bov opens fine under higher boost..

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

removed the bov, checked the operation, everything is fine...
checked the return hose, no kinks or obstructions...

Josh, I know the Synapse is an ugly piece of equipment, but it is the ONLY bov designed for our cars to eliminate flutter/surge.. and while flutter/surge may be common on our cars, it is unhealthy for the turbo...function over form I say.. Im still trying other options, i may see if somebody is willing to switch bov's with me to test if its the bov... Rich, you're coming up tomorrow, think we can put your bov on my car real quick?

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

I found some worth yinfo, thought Id share:

http://www.youtube.com/watch?v=MU5Y6d9rh1k&eurl=http://synapseengineering.com/smf/index.php?PHPSESSID=b125966bbb8e479f9938562834c73abf&topic=30.0

Compressor surge happens this way: Turbo is spinning many thousands of RPMs at engine WOT (wide open throttle) -> throttle shuts -> pressure builds up between closed throttle and still spinning compressor wheel -> pressure has to go somewhere so it stops the spinning compressor momentarily to pass air over and over again -> So you hear tsssch tsssch tsssch tsssch -> each successive tsssch is air passing the compressor wheel out the inlet of the turbo in the other direction from where it is supposed to go -> Turbo slows down and stress is put on the common shaft because you have to remember that the exhaust is still torquing the turbine wheel to spin the compressor.
Many other manufacturers make the mistake of chasing higher flow rates on their BOVs simply because their designs can't actuate fast enough. What good are high flow rates when the turbo is flutterdumping? Let me define flutterdump. Flutterdump is when the compressor surges, then dumps the air seconds later to get rid of the surge. The goal is to eliminate compressor surge, not just delay it. The goal also is not to have a BOV that makes the turbo surge below a certain boost level, only to work at higher boost pressures. This is a design flaw whose goal is for the BOV to stay shut at idle instead of ridding the system of compressor surge. That is why those designs have you selecting springs based on your idle vacuum level, because all they care about is staying shut at those idle levels. The thing you have to remember as a street user is that you are not running max boost all of the time. To the contrary, in every gear you are probably making less than 4 -6 psi of boost. Compressor surge at 95% the life of your turbo is not acceptable. And for the racer, compressor surge at part throttle, or corner throttle modulation should not be acceptable either when there is a simple solution, Synchronic BOV.

All this info, and more can be found here: http://synapseengineering.com/smf/index.php?PHPSESSID=b125966bbb8e479f9938562834c73abf&topic=30.0

I am starting to believe that the push/pull type spring bov's are not the answer for our car..

Opinions?

Just4fun · Postby **Just4fun** » Thu Nov 13, 2008 9:14

It seems the problem is with the BOV. You said you had removed the spring and piston to oil them. Any chance you have different spring rates to try to adjust to your car?

edit to add: Maybe a weak vacuum signal?

SpeedRacer · Postby **SpeedRacer** » Thu Nov 13, 2008 9:14

Here's the thing. Mine is almmost exactly like that Eric. It was like that ever since I put it on. More noticable after the FMIC of course. Only when I'm boosting 0-8psi will it do that though.

tbot · Postby **tbot** » Thu Nov 13, 2008 9:14

yeah but josh, eric is being cautious about everything and there's nothing wrong with that and something to be said for it. To me it does sound like something wrong w/ the BOV, but since I dont' know much about this subject i won't inject my opinions. Eric, I would talk with Nissan Dave, he actually knows quite a bit about this stuff, I'll see if i can remember to ask him tomorrow when I'm talking to him.

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

SpeedRacer wrote:Here's the thing. Mine is almmost exactly like that Eric. It was like that ever since I put it on. More noticable after the FMIC of course. Only when I'm boosting 0-8psi will it do that though.

HERES THE THING, JOSH..lol

"Only when I'm boosting 0-8psi will it do that though."

Compressor surge at low boost means the volume flow fo the bov is not capable of relieving the amount of pressure the compressor (turbo) is creating..

Read what I posted again, and read all of it... IT IS BAD FOR THE TURBO... yeah yours was like that ever since you put it on..all that means is yours is wrong also.. if yours sounds like mine, you definitely need to correct it. I have heard from Turbosmart and Synapse, as well as Cp-e, and it is indeed compressor surge. Im not saying that everybody who owns a diaphram type bov for the speed has the wrong part, but I will say that every push type bov will create compressor surge on a speed...at one rate or another, and by definition, that is bad for the car. A small amount of compressor surge is "ok" at lower boost (under 8psi), but with all my bolt ons and mods, Im not willing to risk something like this.. simple as that.. If I can eliminate a potential danger for my engine, why not do it? Just because everybody elses sounds like that, doesnt mean its right..

Plus, if you read more into the Synapse, it is the quickest acting bov available right now, its the only pull-type for our cars, which means it seals TIGHTER as you create more boost...rather than relying on a spring to hold it back... no possibility for it to leak ANY boost. I dunno, sounds pretty good to me

firestoned · Postby **firestoned** » Thu Nov 13, 2008 9:14

Just4fun wrote:It seems the problem is with the BOV. You said you had removed the spring and piston to oil them. Any chance you have different spring rates to try to adjust to your car?

edit to add: Maybe a weak vacuum signal?

no spring options, I believe like Josh said, the surge has always been there, its just noticeable now with the front mount intercooler...

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