Clarify the BOV for me

[SeanCucf]

Alright....my understanding is the BOV's for our skis is a vacuum operated unit, which only releases pressure in OFF throttle situations. As such, it would better be termed a pop off valve, or whatever. In no way is it like a turbo BOV which limits boost, but instead only opens in the absence of boost (via the vacuum line), and the valve is closed under throttle/boost, right?

So, ignoring the definition of a "True BOV", it only vents pressure when the TB is closed and there's no pressure in the intake manifold which in turn allows the BOV to open and release pressure, right?

I'm going nuts on the other board with guys arguing (I know I bring it on myself)

tell me I'm right

[RX951]

Blow off valves are air pressure release valves that can be mounted on the intake piping of a turbocharged or supercharged motor anywhere in between the turbo/SC and the throttle body. They are also known as dump valves, or vent valves.


http://minimopar.knizefamily.net/perf/bov.html

http://www.alltrac.net/tuning/bovfaq.html

[SeanCucf]

ahh....yup, exactly what I was saying.....just more intelligent

thank you sir.

[Vern]

Most modern turbo or centrifugal SC setups incorporate a BOV similar to ours. The throttle blade is 'ahead' of the intake manifold, and the BOV 'sensor line' is plumbed to the intake manifold. When you are WOT, there is boost pressure in the intake manifold, and the BOV is closed. When you cut the throttle, the throttle blades close, boost 'stacks up' behind the closed throttle blades, yet the intake manifold now goes from boost to vaccum ... the vacuum sucks open the BOV, releasing the boost stacked up behind the (closed) throttle blade. This works the same on our skis, turbo or centrifugal SC cars.

What turbos use to LIMIT boost is different, its a waste-gate. It has a valve in the exhaust piping before the turbo, and a sensor that measures boost. When the boost hits the pre-determined maximum wanted, the waste gate opens, allowing EXHAUST to bypass the turbo, slowing the turbo and 'gently' limiting or controlling boost. Most modern turbo setups employ both a BOV and a wastegate.

[cskelly]

+1 to vern.

[RMcElarney]

I concur with Vern. Wastegates are used to regulate/control boost on turbos. That or variable vein turbos. Where BOV's are used to help reduce turbo lag (In the case of a turbo) and/or prevent the turbo/superchager from surging the air when the throttle is suddenly closed.

One situation that I've never noticed until installed on my RXP is that the BOV constantly dumps air when the throttle is closed. The advantage of this is it helps to "cool" the air that is in between the throttle plate and supercharger, because when the BOV is not there the supercharger is constantly trying to compress air in which just causes heat to form in the air.

[meeper]

Yes wastegates are used to control boost on turbos, they all still use blow off valves to releave pressure that is the turbo noise you were when letting off.

[RMcElarney]

Yeah exactly. BOV's are relieving the pressure, not regulating the pressure. All boost regulating is done on the turbine side of the turbo. You can run a turbo without a BOV and have correct boost pressures. BOV simply helps the life of the compressor by not surging it with stale air.

[SeanCucf]

yup...thanks guys.

[Danny]

can you put that in a memo, and send it around....cuz that would be greeeeaaaaattttt......mmmmkay, yeaaaaaaaa.....