here's a related thread;
http://forums.rennlist.com/rennforums/showthread.php?t=191518&highlight=bov+vent+atmosph ere
and quotes;
Basically they say that recirculating is better because the air is reused (as oppossed to being lost when dumped)
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I did some data logging with my W/B with the stock bypass valve VS " dump to atmosphere"
valve and it was very interesting. TONS of oscillations with the VAF output when using the dump valve that is properly adjusted.
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Just a waste to throw away that metered air.
Seems to me that since the function of the BOV is to protect the Turbo from the pressure wave of closing the throttle, having boost bleed back to the turbo inlet would be just that much more protection. It seems it would also keep the available boost just a bit higher and the turbo spinning a bit more for when the throttle re-opens.
Or how about this one...
Bleeding boost pressure back to the compressor inlet when closing the throttle unloads the compressor side of the turbo so the turbo keeps spun up a bit even though there is reduced exhaust flow.
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My understanding is that on a mass air flow system, recirculating is best because the mass flow sensor has accounted for the volume of air that has entered the system, when you dump it, the car will run rich for a short period of time.
The idea of prespooling the turbo with the dump charge seems feasible, and that is why even with a map system (TEC3R), we still run a return on our racecar.
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From what I found, recirculating is better. The air is cooler, as it already went through an inter-cooler, when you get back on the throttle there is boost right away, and as Andrew Wojteczko said, maf thinks there is a X amount of air in the intake and will give equal amount of fuel.
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My take on it is that I wouldn't even know why you would use the dump version.
Like others have said, here, all the advantages come from the recirculation type.
The ricers like the dumping 'cause it makes that sound.
Personally, I think it sounds stupid.
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Ventingt to atmosher also gives lag between gears. As previously stated the maf will allow for the sound turst me on that. Very high boost is some times good to vent to atmosphere so that you don't blow lines off. That is my understanding.
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