So I have been experiencing some issues with my car that I think I may have narrowed down to a BOV issue. I first became paranoid when the car started to feel funny when you dropped the throttle in any gear ( like you threw a parachute behind the car). I immediately thought the worst and changed all driveline fluids, and did not see any signs of a shot tranny, transfer case, or diff. Car is smooth as glass at highways speeds with no funny noises.

So more recently I have noticed a faint but audible compressor surge when lifting out of low boost low load conditions. You would hardly tell if you weren't listening for it, but it is recognizable. It would make sense to me that if the BOV wasn't venting right, the car would be seeing some unstable air hence my hesitation. Stock plastic bov, stock ic piping, essentially a stock car. Plugs are new NGK BPR7ES, gapped to .028. I've read a million posts on the bov being installed backwards, fairly sure the bottom of the port is to the Intercooler Pipe, and the top portion vents to the intake side.

Zero spark blowout, car is a rocket when the boost hits but just seems very odd in drop throttle and part throttle conditions ( and between shifts). Any thoughts?

 

Well the plan of attack is to pop in a metal 9 bov and see if that takes care of it. I am thinking that the bov isn't venting properly, and its backing the air up into the compressor causing my hesitation/mild surging between shifts. Pray for me.

 

Check ur vacuum lines.

But even if ur not modding ur evo the metal dv oem 9 is a must. Its sad how bad the plastic one leaks. Even at stock boost. I swapped mine out with a 9 before my synapse dv and the car held boost alot better.

 

I'm glad you said "compressor surge" and not "bov flutter" which doesn't exist.

good luck

 

Yeah, with 100k on the clock it is very possible the diaphragm is torn. I'm hoping it will just make the car drive smoother, and not "chop up" between shifts, the ability to hold added boost will be a plus.

Vacuum lines look good, and I was able to verify that the bov is installed in the proper orientation. Turbo has zero shaft play, doesn't burn or blow oil, and seems to be in great shape.

 

Get the 9 BOV/DV... I was experiencing the same issues that you were describing in the OP, with my original plastic VIII diverter valve... Once I made the switch to the 9 BOV/DV, it fixed it.

Good luck

 

I was hoping someone could confirm my suspicions, I have been digging all day and really couldn't find a definitive answer. Did it also take care of that feeling like the car was falling flat on its face between gears? I swear its like the car will boost great, then you lift and it studders, and you basically loose all of the boost you had.

 

Switch to the IX metal BOV/DV as all these other guys have stated! Im waiting for mine to show up.

 

I tested my brand new 9 a year ago (not cushed) and held just about 27psi before it opened. I have to think crushing it would hold 30 maybe 32 psi.

 

Just got the 9, installing tomorrow.

 

they're cheap enough used to pile up spares too (talking about the IXs) I'm always looking for spare ones


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Alright so the 9 bov is in, holds 23psi fine, works great under hard load/high boost, and I am getting compressor surge like a bastard (low load, low boost/drop throttle). Just had an STM dyno tune done and a hallman MBC in, and I think the vacuum line might be the issue, I think they have it tapped into a three way tee at the boost controller. Going to drop them an email now and see what they think, car runs great otherwise. Stock exhaust, stock turbo with an intake and cone filter.

 

Extremely frustrating. The only other thing noteworthy is that it seems like the turbo is just working too hard to build boost ( revving to the moon). The car is smooth, pulls hard, but this surging on drop throttle in certain conditions is really pissing me off. Is this a side effect of running a manual boost controller or what?

 

Have you done a boost leak check yet?

 

stock valve leaks get a 9mr valve