EvanUrS4

amongst yourselves about why it's bad.

The one person who HAS tried it says it works great.

Interesting. =P

Blake@NWAutoSalon

BOV would vent that to atmosphere messing with the Motronic IIRC. Why would you rather a BOV then a BPV if its just for the sound, save your reply.

MA_2.7t

Which UConn campus are you at?

EvanUrS4

It's not the sound I'm after... I was just curious why the people that actually try it find that it works great despite what all of you say about metered air. Which I do understand... logically makes sense. Just strange that results don't match up.

S4-Fireblade

...can you imagine the German engeneers producing a luxurious car like this with a constant phsss-phsss between gears?

SilberUrS6

Hap is not using the Motronic system. No MAF means no loss of metered air. The injector cycle is set by incoming air mass, so...

For those folks running the Motronic ECU, BOV = not good.

ThetaTau87

Both a BOV and BPV accomplish the same thing. When the throttle closes and creates a vacuum in the intake manifold that vacuum signal opens the BOV or BPV to keep the the turbo from trying to build pressure against the closed throttle and stalling. With the BOV open it vents to atmosphere. With a BPV open it vents back to the intake side of the turbo and recirculates the air. The turbo sees no resistance and can spin freely with out losing much RPM between shifts.

It also prevents huge pressure spikes in the intake tract when the trottle closes quickly after a high boost pull. The inertia of the turbine keeps it spinning very fast even after the trottle is lifted or closed. The BOV/BPV vents this pressure or recirculates it.

The reason the AAN uses a BPV is because it has a MAF the meters all incoming air. If you vent the boost rather than recirculate it the ECU will cause the car to run rich when ever the BOV is open. S4-Fireblade says his car pulls harder after shifts at WOT, but he is probably running rich and decreasing his MPG at part throttle. I suspect that he is getting better recovery and more power after shifts due to the fact that the intake charge is cooler because vented boost is not recirculated. I am really interested to see his part throttle A/F ratios.

Twisted5000

Storrrrrs. (The real one)

UrS4boy

rules would have required no more than a certain dB sound on the street. Hence the quiet exhaust and probably one reason why there is a BPV instead of a BOV. A BOV and its attendant noise on shifting would not have passed the tests back in the day.

Now, who cares, as long as it works?

UrS4boy

However, that is just a guess based on these discussions.