Hello. I am just wondering if the stutter/flutter on the EVO after changing the stock BOV to a "better" one adherent only on the EVO? The reason I ask is because other friends of my have turbos that have a VTA BOV and doesn't seem to have this problem. So is it just on the EVO? I really want that big "swoosh" sound. This is also one of the reason I bought the EVO.

thanks

 

The fluttering sound you're hearing is more than likely compressor surge. Very bad for your turbocharger. Basically it sounds as if your BOV is doing one of two things... not opening enough to vent the aircharge or two, not opening at all. IF there is a tension adjustment on your BOV you might wanna back down the adjustment. This is usually done by turning a set screw counter clockwise.

 

I agree, you didn't specify which valve you used, but I'm assuming its a Vent to atmophere (Because you said you wanted the big swhoosh)

First thing you need to do is make sure the tension of the spring isn't too high (the adjuster screw) and also make sure that your using a light enough weight spring that it will open when needed.

Also, there is a Vacuum fitting on most BOV's, under boost the pressure in the manifold helps to keep the valve closed, and under vacuum it assists in opening it. Make sure its hooked up correctly according to the manufacturers instructions (and not leaking because if its disconnected or leaking it will also make that fluttering noise)

The spring pressure and the adjustment is really just to provide enough tension so it doesnt open "In transition" (too early in part throttle driving) but only to open when there is vacuum in the intake manifold, and positive pressure in the intake piping. Make sure the vacuum source your using is the one that was used for the stock BOV, however any vacuum source at the manifold will work.

So what does all this mean? A little trial and error, if your certain that the spring rate is adequate, you can back off on the adjuster a bit until it doesnt stutter anymore. If you can't, then go to a ligher spring (or in some cases the BoV has an inner and outer spring, remove the lighter of the two springs, or if it has a spring kit, put the next lighter spring in. And then do the same adjusting.

FYI, you may discover you have some idle quality problems and occasional stalling with a VTA BOV.. A VTA BOV Is generally not recommended because of how our air/fuel is metered, venting the air back to the atmosphere will foul up the engines "Knowledge" of how much air is really going into the motor.

 

Hey MalibuJack, what kind of BOV are you using?

And thanks for the info.