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Hi ppl

Great forum...been reading posts to get clued up on the S4 as I am looking to get one near Christmas this year.

I will be looking to modd her slightly...re-map...exhaust system and suspension...that will be more than sufficent for me.

If any one is planning on selling there S4 near christmas time then i will be interested.

Just one question.... does BPV stand for Boost Pressure Valve?

Regards

Khany

Hi - hope you 'enjoy' your reading...

BPV = by-pass valve or diverter valve - this stops the boost from dropping too low when changing gear, thus keeping the turbo spooled! The excess air is vented to the atmosphere.. (someone will correct me if I'm wrong!)

BPV=By Pass Valve, dumps pressure into manifold.
BOV=Blow Off(stop giggling at the back ) Valve which vents to atmosphere. Also makes a loud noise.

Most OEMs now use BPV, mostly because of emmissions I believe, BPV is supposed to offer even better throttle response, although I suspect emmissions is the real reason.

HTH and welcome to the forum.

KayGee

Welcome to the site Khany.

Good look with your search for an S4.

I don't believe that use of BPV vs BOV has anything to do with emissions regulations because the air in question is cleaner than that outside (it has passed thru the air filter).

AFAIK the BPV choice is purely for engine performance/efficiency (avoiding turbo stall as mentioned), and because the ECU uses MAF measurements for fuelling, so loss of air would upset that.

IIRC Audi use the term 'recirculation' when describing the BPVs/DVs. This is a good description because that's actually what happens: When the DVs open they take air directly from the 2 pipes which feed the throttle body and pass it into the y-pipe from the air filter which is connected to the turbos. Thus when the DVs are open, the air flow is maintained, and slightly less air is drawn in through the filter: The air is literally recirculated through the turbos & intercoolers.