During my engine build I decided to stick with the MAF. I am only venting 1/4 of the air to the atmophere, but thats not really my problem. If I slowly get on it let says half throttle and let the boost max out this thinks leaks like crazy (starts recirculating at 5k+ rpms/venting some to atmosphere). Under wot it stays closed, but holding 50-75% throttle it will spray air out even with the spring adjustment tightened all the way.


Scenario - 3rd gear holding at 50-75% throttle, starting going over 5k rpms hear BOV give way and the car loses power (massive boost leak haha)

It even does it under full recirculation. Is this just a bad BOV? I'm thinking its from the back pressure of building 18lbs of boost before 5k. Then the throttle is not open all the way causing back pressure buildup and it uses the bOV to escape. My crushed evo 9 metal bov didnt do that.

Evo 8 turbo only 18lbs of boost (break in tune)

 

Umm.. I own this valve. I dont have this issue. I have had this for 3 years installed. No issues. Mess around with it. Yeah i know it sucks because u keep having to pull over until u get it perfect. Maaaaaybe a bad bov? Maybe it needs cleaning.. idk. Maybe it IS this kind of BOV and mine does the same thing but the way u explained it confused the **** out of me so all im saying now is that its your bov thats jacked and not mine

 

do you have a vac leak? Check the vac line and make sure you have a solid vac source hooked up to the BOV. I had this BOV and didnt have this issue either. Also make sure that nothing is in the vent or clogging it

 

No vacuum leaks at all. Pressure tested all the way to 40 psi without the bov on cause its the only thing that leaks (past the bottom of the inlet piston) which is stated to happen on their website since there is no oring down there to make a perfect seal. The pressure from the going + on the spring doesn't change the opening pressure on the inlet piston either. At least testing the pressure with my thumb. Tightened all the way feels just like it being turned all the way - negative. Maybe i'll take it apart and see if the spring is defective.

 

Mine would gunk up if I let the car sit for more than a week or two. I had to take it all the way apart and vigorously clean the piston. My problem was that it either stuck completely closed causing surge, or stuck partially open which at first felt like my turbo was dead.

I would simply dab my finger in some oil when I would change the oil and rub it around the BOV. Seemed to really help it stay smooth. I was able to back off the spring pressure almost to full soft and had it blow off very smoothly at low boost/rpm.

You can email the company and they will gladly send you the instructions to clean it out. It wasn't too bad and you may not need the instructions but I was surprised how nice the dude was when I inquired.

 

Here is fast go bits very quick response


Hi Josh,
Interesting issue you have there. I know what causes this, but it's unusual to see it happen except under very specific circumstances.

The way our valves work is the use both the spring pre-load and the vacuum pressure to control the piston opening. Under WOT, the manifold pressure is the same as the intercooler pressure, so the pressure on both sides of the piston is equal and opposite, therefore it doesn't matter if it's 5psi or 500psi, the piston won't open.

If there is significantly less pressure in the manifold than the intercooler, there is enough of a pressure differential to allow the piston to be pushed open.

Now, the reason I say it's unusual to see this occur except under specific conditions is because it's not often that a car can build enough boost pressure in the intercooler with the throttle partially closed to cause a large enough pressure differential to cause the valve to open. The only time I've seen it happen was on a car in Germany on the Autobahn at a steady 200km/h, and on an EVO with an FP Red on the dyno when the part-throttle range was being tuned.

Here's the thing - for the valve to be opening with a manifold pressure of 18psi, there must be at least 23psi or more in the intercooler. If possible, I'd suggest tapping your boost gauge in pre-throttle to confirm. This means that the turbo is being spooled too hard at part throttle. The justification for this comment? If you're only at part throttle, why does the turbo need to make maximum boost?

If you were to physically force the valve shut under these conditions, I can just about guarantee the result would be compressor surge, because the turbo is spooling more air than the engine can take with the throttle only partially open. Note that the factory valve under these conditions would also be open.

We're starting to see this a lot on EVOs, because there is a trend these days to mate larger turbo compressors with smaller turbine housings in order to achieve big flow capability with factory-like spool up. The problem is, they spool very well at part throttle and low RPM, typically causing surge at low RPM even at WOT - this is very common with the FP turbos. The best solution in this case is to lower duty cycle under part throttle conditions. This would improve efficiency, because achieving peak boost (actually, significantly higher than peak boost pre-throttle) at part throttle only increases intake temperature and exhaust backpressure, under conditions where maximum power is not being demanded by the throttle.

Now, because I can't see the car and I don't know any of the specifics of the turbo, the tune or the engine build, all of the above is based on my experience and the most likely scenario. To sum up, I don't believe there's anything the valve can do to fix the problem, because even if it could be forced shut under these conditions, I believe you will encounter compressor surge. If I'm wrong about compressor surge, at the very least forcing the valve shut is a band-aid solution - the turbo is simply making too much boost at part throttle.

If you want to confirm this, take the valve out and flip it around backwards. This will prevent it from opening at all (which won't harm the turbo in the short term for the purposes of this test), and if you drive under the conditions you are having the problem, you will be able to tell if it solves the problem or causes compressor surge.

Give it a try and let me know the results