FlyNavy

iTrader: (10)

I have a 366hp Turbo Trix tuned EVO with AEM EMS/TIAL VTA BOV and all the bolt ons. I bought it used recently and overall its great. I believe its running properly, I'm just trying to understand it. When the turbo builds any amount of boost and I let off the throttle at all makes a fluttering air sound like a rattlesnake. When I romp it good and let it off I hear the BOV blow. From thread searching I assumed it was coming from the BOV and was normal or maybe I need a lighter spring.

I opened the hood to see if the flutter was coming from the BOV and it actually was coming from the Intake Pipe/filter. The BOV was closed tight when the flutter sound was happening. Again, when I would give it some gas I could clearly hear the flutter from the intake and eventually a nice even blowoff from the BOV. I trust the TT tune and the car is running great, but if someone could explain what's going on I'll be a little less dumb. My standard "this is my first turbo import after a long line of cuby V8's" disclaimer applies. Thanks!

okijack

iTrader: (2)

sounds like compressor surge. check out gofastbits. they got a good write up about it on their web site.

evo81

iTrader: (30)

Fourdoor just posted something about this in the turbo section about the tial.its good advice

Fourdoor

iTrader: (11)

Yup, that rattle snake flutter is compressor surge. I just replaced my turbo due to a destroyed thrust bearing. I was running way to much boost for the stock turbo, but I also think the compressor surge had a lot to do with destroying the thrust bearing. Now with the new turbo I want to protect my investment, so I researched the possiblility of getting a weaker spring. After swapping to the lightest optional spring I now have ZERO compressor surge

Later,

Keith

FlyNavy

iTrader: (10)

I too am milking my stock turbo and have done about all I can mod wise short of higher octane and water/alc injection. How much boost were you running when you wasted it? Did it go instantly, or degrade? What were the symptoms? What did you replace it with?

Fourdoor

iTrader: (11)

I was getting around 26 or 27 psi on the spike tappering down to 23 psi by 8000 RPM (105 octane unleaded). One run it was fine, then after the next run it was squealing like a damned soul getting the pitchfork when ever I put the car under load. It still makes boost just fine, but I knew what was wrong and that it wouldn't last long so I replaced it with the EVO 6.5 TME turbo from Forced Performance. 10.5 exhaust housing instead of the stock 9.8 with a titanium exhaust wheel and shaft instead of the stock inconel.

The stock compressor can not keep up with the 272 HKS cams resulting in more boost tapper than I would have with the stock cams or 264's, but at this time I can't really aford a significant turbo upgrade so I went with the direct bolt on. With the demands of the 272 cams, running 23 psi to redline is over spinning the living $hit out of the stock turbo. Combine that way out of spec shaft speed with compressor surge when letting off the throttle and you end up with a damaged thrust bearing.

I just noticed your screen name, you a squid? I spent 10 years in as a Nuke on Subs

Keith

PS: Reason I am switching to GM boost solenoid is so I can run 21 psi at redline without having to spike up to 24 in the low RPM range to get there.

FlyNavy

iTrader: (10)

I'm running 272's at about 24psi peak on pump gas. So with the solenoid, the ems is setting your boost? What kind of hp are you making on pump gas? Sounds like our mods are similar.

Yep, squid here. Helo pilot 5 yrs in.

Fourdoor

iTrader: (11)

On a dyno dynamics dynometer I made 311 at the wheels on pump gas and 333 at the wheels on 105 octane unleaded. On an AWD dynojet that would come out to about 366 hp at the wheels on pump gas and 392 HP at the wheels on the 105 unleaded. That was before I did the turbo change, the header, and the O2 housing.

Later,

Keith