For the past week at WOT in 4th and 5th @ 19 PSI and up I get a mysterious flutter. I have tried three different BOV's. One bing the Greddy RS tightened all the way down. I have done a pressure test with no signs of any leaks. The car does not buck when this happens. To me there seems to be a surge of pressure that the engine can not keep up with. The boost gauge needle starts dancing when this happens which means lost of pressure, but why? I am not saying this is a BOV problem but if the BOV is doing the fluttering what is causing this. This is not anyway near the flutter some are experiencing at half throttle.

Anyone have any suggestions on what to lookup for? I am lost on what to do next.

Mods Are:
AMS 3" TBE, Bushur FMIC /w UICP, Bushur Intake, HKS 272 cams, Walbro Fuel Pump, Hallman MBC, ARP Head Studs, Stock Turbo, Exedy Hyper Clutch

 

Do you have adjustable cam gears?it sounds like a timing or overlap issue,also try using a reference line from the intake-mani instead of the one off the turbo outlet,the air is more stable inside the plenium,and the t-body is like an on and off switch for the boost controler ,kind of like the concept of air pressure regulation on an air tank,press off the tank not the pump where its not as stable

 

If you tried the stock BOV and still have the issue, it'sdefinitely not the BOV. Have you tried the stocker? If not, do it.

 

Spark blowout? Might tighten plug gaps. Interested to hear. Good luck.

 

I had the same problem a few weeks ago. Car would flutter really bad at WOT above 6000rpm. I have the 1G BOV and it never did it before and it hasnt done it since.

 

Yeah I have the stock BOV on now and it still happens. I dont have cam gears so dont think its overlap. As for the MBC I guess I could try the source off the Intake Manifold can't hurt. will keep you posted.

 

Is it breaking up at upper RPMs? If so then its likely to be spark plugs. How many miles do you have on them?

 

Not really. It seems to do it only when you build boost slowly like on the highway and you go to pass someone if you know what I mean. I have launched it from stop to 90 mph and did not do it.

The car has 18500 on it now. So from your post I would have to say no because when cruising in 5th and then go to pass someone it will do it.

 

Going to check spark plugs and gapping and change if needed. Going to double check timing and make sure everything lines up also.

 

Does it only happen in 4th & 5th when you build full boost at low RPM's? Does it correct it self as the RPM's increase?

 

Yeah, to both. You had the problem?

 

Anyone else.

 

Take off your intake and check for excess shaft play on the turbo,,could be shaft walk

 

Nope, already checked it when I did the pressure test.

 

Is your car an Evo VII, really? What I really would like to know is what turbine housing you are running and whether it is ported or not? If you have an unported 9.8, then I think that going to a ported 10.5 would most likely cure your problem.