BPV vs BOV...which are you running?

[Pearldrummer7]

I'm building an 818R, and am using a 257/205 hybrid motor with forged internals. I have a FMIC which obviously won't work on a rear engine car. I'm probably going with either a stock or an STi one.

Mated to that, I have a TurboXS 50/50 hybrid BOV. I'm not quite solid on the implications of the hybrid system, but (in layman's terms) I believe it recirculates under low pressure and vents to atmosphere under high pressure.



What are the issues with running something like that on our cars with a well-done dyno tune? Versus a stronger BPV, let's say.


Thanks for the advice!

[Wayne Presley]

Both work well but if you are using an ECU that uses a mass air meter you need a bypass valve. Otherwise the ECU will inject fuel for air that went by the meter that didn't make it into the engine...

[Pearldrummer7]

Both work well but if you are using an ECU that uses a mass air meter you need a bypass valve. Otherwise the ECU will inject fuel for air that went by the meter that didn't make it into the engine...

Ah, makes sense. So, is there a clear definition of what ECUs use a MAF and no MAP? (is that right?)

[JeromeS13]

It depends on what your tuner uses. The stock ECU can use MAF tuning or Speed Density.

[305mouse]

I went from a BOV back to an OEM BPV on my old car. It was tuned with the BOV, but I had more consistant results with the BPV. I used the STI one, which held a higher PSI than the WRX one. I believe the 06 and newer WRX's used the same BPV as the STI. One has a Z marked on the top, but I forget which is which. My car held a peak boost of 24 PSI with that BPV.

[Wayne Presley]

Ah, makes sense. So, is there a clear definition of what ECUs use a MAF and no MAP? (is that right?)The stock Subaru uses the MAF.

[Evan78]

If you're using the Subaru ECU and not switching over from the OEM MAF metering system to speed density, BPV will be the least troublesome. If you want to have endless reading material, blow off valves that vent partially or completely to the atmosphere (and the problems potentially introduced with this setup) have been covered very extensively on NASIOC.

[wleehendrick]

So when is an aftermarket BPV/BOV needed? My motor is mostly stock 06 WRX; Cobb intake, silicone inlet and hoses, TGV's gone, bellmouth to 3" cat-less exhaust. I'll be tuning with a Cobb AP, and probably use an OTS Stage II map to start with before a custom tune. If I replace the stock BPV, it would be with a recirculating unit, not a true BOV (vent to atmosphere). So, would an aftermarket BPV provide any benefit with the stock TD04 turbo, or is that only warranted with much more boost than I'll likely be running?

[Wayne Presley]

So when is an aftermarket BPV/BOV needed? My motor is mostly stock 06 WRX; Cobb intake, silicone inlet and hoses, TGV's gone, bellmouth to 3" cat-less exhaust. I'll be tuning with a Cobb AP, and probably use an OTS Stage II map to start with before a custom tune. If I replace the stock BPV, it would be with a recirculating unit, not a true BOV (vent to atmosphere). So, would an aftermarket BPV provide any benefit with the stock TD04 turbo, or is that only warranted with much more boost than I'll likely be running?

You will be fine with the stock bypass valve.

[wleehendrick]

Thanks Wayne!

[metalmaker12]

Stock unit is very good for the stock ecu settings.

[metalmaker12]

I'm building an 818R, and am using a 257/205 hybrid motor with forged internals. I have a FMIC which obviously won't work on a rear engine car. I'm probably going with either a stock or an STi one.

Mated to that, I have a TurboXS 50/50 hybrid BOV. I'm not quite solid on the implications of the hybrid system, but (in layman's terms) I believe it recirculates under low pressure and vents to atmosphere under high pressure.



What are the issues with running something like that on our cars with a well-done dyno tune? Versus a stronger BPV, let's say.


Thanks for the advice!

With stock ecu use the stock valve. Also get an awic

[ssssly]

As stated for stock pressures, the stock BPV will work great.

Though if you find yourself wanting to push over 19 psi, it won't hold.

I have had great results with my Tial BPV for high psi applications. Is the same unit as their BOV with a modified bottom housing that turns it into a BPV. They call it their "Q" model.

Very fast response, flows a ton of air and you can retain your stock MAF tuning.