jw_snowman

Anybody know exactly what the difference between a Blow-Off Valve and a Bypass Valve are? And if there is a difference, what does the RDX use as a pressure release system for the turbo?

mingo

blow-off valve vents the charged air to the atmosphere and is a lot more audible

bypass valve aka recirculation valve recirculates the air into the intake. it's quieter and cars with mass air flow sensors need it to prevent stalling.

both are arguably just as effective.

jw_snowman

There's a bypass valve in the RDX right?

cwepruk

Yes there is. Most (if not all) modern factory turbo cars come with bypasses.

They are bascially the same thing - it's just where they vent to. Bypasses keep all the metered air in the system and are quieter.

jw_snowman

Because of this difference in the way they vent, you can't interchange the two eh?

Samdog-1

I'm inclined to think the bypass valve is more efficient because the compressor does not have to work as hard to replace the pressurized charge air (more retained psi contained in the duct) that the blow-off wastes to the atmosphere.

But the blow-off sounds cool.....

stevel

blow off valves are two things.... old school, and rice. old school technology or kids that want the "sound".

bypass valves recirculate the boost into the inlet side or the turbo... this not only retains metered air, but it also, to a point anyways, maintains the turbo spool up. instead of the exhaust spooling up the turbo, the added pressured air put to the inlet side keeps it up to speed. this can function when the auto trans shifts, so you get the boost back quick, or upon closing throttle momentarily for whatever reason........

recirc valves are more beneficial in every practical way.

JGard

You can swap the two if you'd like, people do it all the time.

The only "problem" is that the air that's within the intake system has already been metered by the ECU, thus if you blow it off to the atmosphere with a BOV, there's less air in the system than the ECU thinks, so once you get back on the throttle, you're going to have a temporarily rich condition.

cwepruk

I've heard of the temporary rich condition as well and that it could affect performance but I would also think that being an auto trans, it wouldn't be much of a concern for performance since at WOT, there really isn't blow off like when you go 0-100-0 throttle in a manual trans.

Still, if you want the noise - just buy a CAI. Plenty (too?) loud.

DeEjAy_LiM

The noise is only noticeable if the stock BPV is replaced. Getting the CAI will only make the stock barely audible. It'll only make a muffled whooosh sound.