legacycentral bbs

So.... I am currently running a Greddy Type S blowoff valve (yeah, I know.. I changed over to the HKS SSQV several years ago when I realized how badly this Type S leaked, but the HKS valve has since developed a leak of its own so here I am)...

and of course i suspect it of leaking. Intercooler piping is solid and just built, but boost spikes to 14psi and quickly drops off. If I let off the throttle after the spike, the blowoff sound is barely even audible and this is being vented to atmosphere. I know, I should run it recirculating... but I dont have that plumbed in yet and for now I want to run atmospheric.

So, I know a WRX metal bypass valve will do the trick, but I havent been able to find one (or at least when I looked I didnt look hard enough), so I looked into alternative solutions for funsies. Found a bosch bypass valve that is apparently a stock part on Porsches, and apparently the Porsche guys run them with higher boost and never upgrade the valve because it holds just fine. Also, it is for sale on turbonetics.com for $55. Just look for on that page for the product named "STREET / STRIP BYPASS VALVE"

PN 30359 $ 55.00 Great insurance for up-graded turbos and streetable high performance engines. Manufactured by Bosch this OEM quality light-weight compressor bypass valve features 1" hose connections and the highest flow capacity of any unit offered in this size.

...Then I got to thinking, what if I still didnt want to run my recirculation hose yet? Could I actually run this BPV vented back to atmosphere?

The answer is apparently yes -- if I install a 1" check valve onto the outlet of the BPV to ensure that this does not become a large vacuum leak when not pressurized / in between shifts! Interesting....Lowes has a 1" check valve in stock right down the street. VERY interesting...

Interesting enough to try? That depends on whether or not I can find a WRX metal valve for a reasonable price. Or perhaps figure out how to repair my HKS SSQV, which would be ideal.

What do you guys think?

Found what appears to be the same bypass valve I found linked from another post stating they run these valves all the time with 500HP and have had zero problems with them.

Google Shopping Bosch bypass valve

...and it looks like I can end up with one of these ordered online (not over the phone like turbonetics would have been) for $50 shipped. Neat. Very tempted to get one of these valves....

I would first inspect the HKS diaphragm for a any holes. If so, you could possibly buy a new diaphragm or make a repair.
I've experienced problems with HKS BOV's through out the years and have had success making homemade repairs i.e. super glue patches.

But for that reason that I've had problems with HKS BOV's through out the years, I would have to vote that you try out this $55 Bosch BOV and report back to us if it was a fail or success .

Might as well try it. I have had zero issues with my current HKS but my last Greddy also leaked.. Dunno

I feel that the 1" check valve would still cause restriction while venting the air which would cause some of the boost to flow backwards to the compressor housing.

I'm not even running a BOV just straight compressor surge. It's not going to cause a problem. Anything less than 15PSI (which a little bit of unvented air going back to the turbo won't be) on a journal bearing turbo isn't enough to cause a problem. I've had my setup like this for awhile at 12psi with no issue.

Plus it sounds amazing, so...

Forget about the 710N's. I went through 3 of them on my A4 @18psi. Got a Forge Splittr piston type DV, bigger turbo, and ran 24psi all day with no issues.



Unless you want a shitty diaphragm style DV that will rip and sound like old man farts every time you get off the throttle that is... In which case, get a 710N.

This is good info. Ty

There is a metal valve that is the identical shape as ours. I don't recall the brand/manufacturer, but believe it was OEM for one of the car manufacturers.

The supra single turbo bpv is prob what you are thinking of, Josh.

Hmm, sounds interesting. Maybe i can find a part number. There is a yota dealer right near me, too.