I've had mixed results with the Tial QR recirculating BOV at partial boost, seems that trying to do about 20 psi makes this BOV flutter like no tomorrow. I get zero compressor surge at WOT even in 5th gear on my GTX30 single scroll turbo but trying to hold around 50% throttle in transitions on the road courses is a brutal exercise in futility, she wants 15 psi or 25+ psi and no in between. Also this isn't the flutter you get on the stock BOV at 2000-3000 rpm at 5 psi, but car shaking flutter from 4000-8000 rpm any time you try and hold it at 20 psi.

I've reduced the Mivec exhaust retard from -10* down to -5* in the 160+ load areas where it was possibly staying to high for too long but it only helped a little bit. You wouldn't think the BOV would be forcing me to change the tune to a less responsive setup that worked great with the Works BOV. I have a 4-5mm vacuum line running from the Intake Manifold to the BOV which has the same internal diameter as the Tial QR fitting.

I'm using an 8 psi spring in there right now which is ~16 vacuum and possibly slightly too weak for my setup as my idle vacuum is ~17 or -8.5 psi. Originally it was ordered with an 11 psi spring and it was so stiff it would buck the car like crazy when trying to do partial boost. I also have a 10 psi spring but fear that might be too stiff again which is why I went straight to the 8 psi spring as the first test and figured it "should" have the best drivability.

What springs are people using on their Evo X's with medium sized (~63 lb/min) turbos with success?

 

Update: I did some more testing with the Mivec maps reduced from where I had them and the flutter is much less pronounced than it was before. I guess this turbo is so spool happy with a large compressor that it wants to create some part throttle compressor surge like effect where the engine just isn't consuming all the flow it wants to give. At least that is my theory why reducing the Mivec Exhaust retard is helping it smooth out.

 

One last option would be to try an even lighter spring.

 

I have the same issue - anything in the middle = the jerky jerkey - it wants you to lay into the throttle all the way... was going to try a lighter spring, but Im kinda used to it now...

 

I had the same issue with my Suby. It had a 20g and it ended up being my spring pressure was all messed up. That's what I get for going with a cheep-o BOV though.

 

I understand this is an extremely old thread but seeing how the forum isnt very active in some areas, this should be a big deal.

Did you guys ever figure this issue out? I am having the same issue in my X as well. Doesnt flutter per say, but stays open when at partial throttle and runs extremely rich. Does not close when I go full throttle from partial. Only closes as I let off the gas a bit and then put the pedal to the pedal to the floor

 

I had the same problem. I was told the jerking was from too stiff a spring. I changed my QRJ spring to the pink 1.5 psi spring and no more bucking.

 

The Evo X needs the 6psi spring when running a TiAL QR. running one on mine and I have no part throttle flutter at all. Even in 5th on the freeway I can add some throttle without the thing bucking and freaking out

 

Interesting. But wouldn't a lighter spring cause the valve to open easier under partial throttle conditions? I can't verify what spring I have in there now as it is being built atm but I will check when I go to shop to drop off more part


e_kobz: I noticed you are in az and according to your sig. You have done some nasa racing. Is that something you are still into? Would be Awsome if we could have lunch or something some time an maybe you can give me a few pointers on what to expect my first time at the track?

 

Yes. I have a QRJ recirculating valve. So it's going to be different with a bov. My bad.

 

People confuse the QR and QRJ all the time.

In my opinion, the QRJ with 1.5psi spring is literally the best bov I have ever used in all situations, even better than stock. The way the QRJ is designed, you can use the light of a spring without issue. I have zero flutter or surge on a built 2.0L with cams and a vband 5858. Even in 5th gear low rpm, higher load (like maintaining speed up a incline) where the stock frame turbos would be flutter and surge city.

 

Part of your great experience is likely do the turbo never hitting the surge line like a stock frame turbo does.


To the guy concerned about the valve staying open and running rich, are you running a VTA BOV with a MAF? If so, there's your problem..

 

Yes of course, however I did use my oem bov when breaking the motor in and there was flutter which went away with the qrj

 

No sir its not vta. Recirc and maf.

 

You mean a problem like this ? My tial qrj does this with -3.0 psi spring https://streamable.com/ugcnx