BOV Question

rellow88 · 08-19-2012, 07:24 AM

I have read a lot about recirculating the BOV. My question is how the the ecu compensate for the extra air coming in. The are is dumped in after the MAS so if nothing is metering the extra air how does ecu know how much fuel to add. From reading it seems to be half and half that people have problems or not. I was wondering any actual test have been done about recirculation or not or just a conclusion that it shouldn't be done?

slayer450 · 08-19-2012, 07:38 AM

It's not letting air in, its letting metered air out.

njclimber36 · 08-19-2012, 07:39 AM

The air getting dumped back in after the MAF has already been through the MAF when it originally entered the intake stream. The ECU compensates by figuring the air is going into the engine because it can't go anywhere else, although it might be slightly delayed by being recirculated first, it doesn't seem to be much of a problem.

tkelly27 · 08-19-2012, 08:02 AM

A person "not having problems" with venting a BOV with a draw through MAF is just ignoring the black smoke between shifts, increased fuel consumption, and carbon build up on their exhaust pieces.

Mind over matter; you don't mind, it don't matter.

Yes tests have been don with dataloggers. When the TPS value goes down after a high flow condition (indicating an open BOV) you'll see the logged MAF value go up, the injector pulse width go up, and the Air Fuel Ratio drop below a measureable value.

jtmcinder · 08-19-2012, 08:12 AM

Quote:

Originally Posted by slayer450

It's not letting air in, its letting metered air out.

Actually, many such valves are open at idle, which, in this case, would let unmetered air in. If you all (where "all" means that this is aimed at many more people than just he or she quoted above) would start calling it by a correct name, such as "compressor bypass valve" (CBV) or "diverter valve" (DV), you'd be less confused about how it works.

rellow88 · 08-19-2012, 09:56 AM

Ok sorry to open such a debate I am New to dsm and I just didn't understand how the ecu compensated the amount of air thanks for your input.

jtmcinder · 08-19-2012, 10:12 AM

No problem, but it's not a debate and it's not just DSMs. Just about every turbo car works the same way. And my pet peeve about DSMers calling the valve by the wrong name is probably more for me and my therapist than for the rest of you. The only time - in my experience - when the use of the wrong name caused significant grief is when the SCCA temporarily stopped 2G owners from back-dating their CBV to that from a 1G partly (mostly?) because we kept calling it a BOV. You see, a BOV is a boost-limiting device and those couldn't be touched in Street Prepared back then. But a CBV is not meant to be a boost-limiter, so we should have been able to swap it.

What I find amusing in these discussion of "venting a BOV to atmosphere" is how all real BOVs do exactly that. Only CBVs (aka DVs) are recirculated. And if the car hasn't been switched to speed-density (which I shall leave for you to search for or Google), then the CBV must be left as recirculated.

Tiki2777 · 08-19-2012, 10:12 AM

Quote:

Originally Posted by jtmcinder

Actually, many such valves are open at idle, which, in this case, would let unmetered air in. If you all (where "all" means that this is aimed at many more people than just he or she quoted above) would start calling it by a correct name, such as "compressor bypass valve" (CBV) or "diverter valve" (DV), you'd be less confused about how it works.

blow-off valve.