Recently bought my EVO 5, it's pretty stock. Stock BOV, stock I/C, Monstersport I/C pipes and intake. But this past weekend was the first time I took it out and drove it hard. So I got to experience it having compressor surge. Anytime I'm boosting, full throttle, or partial throttle lift off, You can hear the BOV flutter, and feel the engine and whole car buck. Super annoying and a bit dangerous when feathering the throttle around a turn.

So I took it home and inspected what I could. I took off the Vacuum hose at the manifold for the BOV, and hooked up a vacuum pump like the one below to test the vacuum hose for leaks, and the BOV for operation. No leaks and the BOV opens and holds open under vacuum. The one thing I did mess with was my throttle cable had a little slack, I thought that might have had something to do with it because it might have been closing too soon... Shot in the dark... but it didnt do anything. I dont think I have a boost leak. My car runs fine.. I have a boost gauge, that reads normal....

Sooo any ideas on where I should check?? I've heard of a Stock BOV loosing strength and not being able to hold high boost, but never a stock one that was too strong.


used this to test:

 

Check that it is in correctly and not backwards.not very familiar with evo 5s but id start with that.

 

It is installed correctly, I installed it backwards just to check it out, and still same thing.

 

crickets....

 

Check for a crimped or pinched vacuum line mabe? Doo yu have a. Boost controller?

 

yea have a greddy profec-b...

 

Is the valve crushed? This kill response with stock turbo setup

 

I dont think so, it's the plastic stock BOV

 

That's the next step, at the moment, I dont have one to swap with... Honestly I think that's gotta be the problem...

Japan rocks as always... My evo 5 makes it all worth it. By far the funnest evo out of all 3 versions I've owned.

 

Got my hands on another stock BOV. Fixed the problem. must have had a tear in the diaphragm causing the flutter and surge.