it's the blow off valve

 

Thanks for the reply.

 

I was replying to the OP, but to respond to your post, it's not damaging to the turbo or anything else, it's just annoying and it's not running the way it's supposed to. I had a synapse DV on my old EVO IX MR, and I didn't have much issue with the part throttle flutter. The reason you get the flutter is because the springs in aftermarket BOV's are stiffer to hold high boost. They work best in ON/OFF situations. When you get to situations where they need to open or close slowly, or be partially open, they have problems, so they chatter. The stock unit doesn't have that issue because the spring is soft, and it allows some leak by because it is designed to favor driveability over all out boost holding performance. The stocker is good up to around 25psi (more if you do the crush mod), so if you are running less than that, there's no reason to be running an aftermarket BOV.

 

Thanks.So in my case I need what i'm running because I'm at 27 psi.

 

yeah, you might just want to try a different BOV. The synapse DV is a good one. Holds up to 60psi, and I didn't have issues with fluttering. I think the Forge DV was also a good one. The best one was the APS twin vent, but they stopped making them like 2 or 3 years ago.

 

Thanks i'll check it out.

 

I also have this issue occasionally with my 9-MR bov. It's gotta be your greddy bov, try adjusting it if u can but if not then it seems like its time for a new one.

 

I have this issue currently. My BOV is from an EVO IX. I found this out as I was passing a car on the highway. I gave it WOT again to look at my boost gauge and Boost guage was bouncing at 25PSI. 25 PSI is where I am set to, never had this issues until yesterday. Also I am on my stock tune, since I have to recover from my clutch expense, so need a retune for 91 octane gas, since I was originally tuned for 93. Going to take the BOV on and off to see if it does it, also going to play with the stock EVO VIII BOV as well. Just to troubleshoot things.

 

Wait until you go SD and run a VTA, you'll have to change your driving style to avoid or minimize your flutter. With a DV, it's minimal, but it's still a Turbo'd car.

 

the EVO 8 BOV will probably be even worse. The EVO IX valve is metal, while the EVO 8 valve is plastic. The 8 valve is notorious for fluttering/leaking/generally sucking.

 

i still seems to have the flutter problem
the oem 9 dv got rid of part flutter in the lower gear but still seems to does it in 5th gear (trying to pass someone on freeway)

 

I think it's relatively normal to get a tiny bit of flutter in 5th gear in that kind of situation. Even when my car was stock I remember it doing that. As long as the car isn't bucking or unsettling I think you'll be okay.

 

Flutter is normal for higher load low rpm situations even on the stock turbo. It's much more of an occurrence with a larger turbo, even with the stock DV.

 

Its your BOV. The car flutters because not enough boost is being built at lower rpms. Happens to me in 5th gear around 2-3k rpm and I have the stock 9 bov. You have to either let off the gas or downshift to fourth.

 

Its ur bov stock 9 or tial work good