So I recently had my 03 evo 8 tuned. its on the stock turbo and make 300/285 on 22psi. I have a older turbosmart bov with what appears to be the yellow spring (has small specks of yellow paint on the inside of the coils). but under 3/4 and sometimes full throttle I can hear the turbo spoil and then a big rush of air that sounds totally different than the spool as well as the turbo fluttering under throttle. I was thinking I have either a spring thats to weak, or just my yellow is worn out.

 

If you have the wrong spring, basically whats happening is you have a spring rated for a certain vacuum, and you either pull more or less vacuum than what the spring is rated for, therefore, when you have a stiff spring, it flutters when you let off the throttle and do not make enough boost/vacuum on decal to get rid of that charged air, or the spring is too soft and can cause the valve to get stuck open at idle and suck in unfiltered air, this will cause lots of other problems as well.

as far as stiff springs go, makes you sound like a ricer ( but deep down we all love the sound) Overtime, this flutter can cause shaft play of the turbo since all the air that can not be dumped with the blow off valve escapes through the compressor wheel onto the air filter, therefore giving it that tututututu ricer sound. lol, cant believe I actually typed that. hope that helps ya man.

-Roni

 

Ok i understand what you're saying, but if mine BOV or spring is messed up, could it be cracking up open under high boost/WOT? because that's my last thing to check but my fox body is currently taking up all my jack stands so I can't really check

 

More than likely your spring is fine, -and your diapragm is more likely to be the culprit. This is not an expensive fix, you another bov and have ease of mind.

i have a forge adjustable bov for sale btw, $85 shipped

 

roni have a newb question I recently went with air desnity so my tial q is now an atmospheric one at idle should I feel any air coming out of it bc I do now not sure if thats normal

 

not to sound like a ttwat(this is my first evo/turbo car). iv taken it apart and there was no diaphragm to speak of