Interesting problem with a maf system...
 

Background:
'03 Evolution 8, 16g6 turbo with 10.5cm^2 hotside, Brian Crower 272 degree cams, stock FMIC for now, Injen intake kit and hard IC piping, HKS 3" dp and full turbo back exhaust, Megan Racing cat delete, boost set at 22psi solid to redline through EcuFlash. Stock maf setup.

Problem:
I removed the stock diverter valve to replace it with a Turbo XS Type H34 recirc valve. For some reason with just the spring in it and no shims it likes to die out when coming to a stop, similar to what a vta setup normally does on a maf equipped car. It doesn't leak, but when I shim it out to correct for the stalling issue, I get massive compressor surge everywhere...low boost, high boost, it doesn't matter. The stock plastic diverter valve has a much higher spring rate than the Turbo XS piece, but doesn't surge at all.
Anyone perhaps have any insight on this? I know it's a long shot on here, but hell...it's worth a try. :P

Re: Interesting problem with a maf system...
 

I know vtec this me know

Re: Interesting problem with a maf system...
 

mabey you put too big of a shim in it?

Re: Interesting problem with a maf system...
 

my bet is that its stalling because its not re-routed back after the maf since the maf has already counted the air and youre letting it out. By shimming it a lot you are keeping the bov from opening, which is getting rid of the stalling problem but is now causing compressor surge. just a guess

Re: Interesting problem with a maf system...
 

Lol funniest thing I've read all day :)
I've tried everywhere from no shims up to 8 shims, and it does it no matter what.
It's still setup as a recirculating valve and does enter back in after the maf, which is the way the Injen intake/piping kit has it setup. Putting the stock plastic valve in makes the car drive normal again, which is pretty weird considering there shouldn't be much of a difference between valves other than spring pressure.

Re: Interesting problem with a maf system...
 

that shitty DV probably has a torn diaphragm.

Re: Interesting problem with a maf system...
 

hmmm...something must be wrong with the bov since if its recirculating it shouldnt have any negative effect on the way the car runs really. take it apart?

Re: Interesting problem with a maf system...
 

so the new one has a weaker spring? maybe you can ry to put the stock spring in the new part? the weaker spring could be giving in the the pressure. im just taking a wild guess on this one so dont take me too seriously.

Re: Interesting problem with a maf system...
 

i dont recurculate my bov, shooting flames is where its at :6

Re: Interesting problem with a maf system...
 

How far from the maf is the return tube in the intake pipe? I hod some occasional stalling issues and maf spikes when running a 2g dsm with a homemade intake. The recirculation pipe was too close to the maf and too close to perpendicular with the intake pipe. It went away wehn it was piped in closer to the turbo. Figured out it was blowing air back through the MAF the wrong way, leading to a large intermittent spike in airflow.
Is the BOV the only thing on that vacuum line, or does it share with anything else? The turbo XS valves have a very heavy piston rather than a light plate like a type-s or the stock valve so in my experience even when shimmed right, they can still cause slow response and compressor surge from the weight of the piston. Something else sharing the BOV vacuum source (like an MBC many of which have a small vacuum/boost leak) can reduce the vacuum signal and make the problem worse. All that sliding surface area makes mine pretty inconsistent in response too. I've had it freeze shut in the winter from a couple drops of water etc.

I'm not very impressed with my Type H, its a good thing it was free.