[MR2] <MKIIT> BAD BOV!!
briank at glmotorsports.net
Fri Nov 30 07:41:13 EST 2007
> Thanks. Who makes/made this one?
That was an HKS product.
> Still don't understand what this component has to do with recirc or not
> recirc. The Deuce has a Greddy Type R; the "exhaust" is open to the
> atmosphere and I see no means, blocked-off, to feed it back to the intake.
> This is not to mention that I have never seen how that would help. The
> of the BOV, as I understand it, is to reduce the amount of mass going into
> the engine, so just feeding that mass back into the intake doesn't seem to
> accomplish that objective and would seem to negate the purpose of the BOV.
It matters because it changes the way the air is metered (and when).
With a VPC, the air is effectively metered as it enters the TB (after the
BOV). A factory air metering system measures the air pre-BOV. If you let
air out at the BOV, the factory system has already registered more air than
you're actually getting and a rich condition results. If you push the air
back in, pre-turbo, but post air metering, then you maintain the proper
The BOV's only purpose in life is the release pressure so that the
compressor wheel doesn't get forced to a harsh stop when the throttle
briefly closes during shifts. Causes lag and abuses the turbo (Turbo
Esprits don't use a BOV. One of the first mods done is to add one as it
greatly increases turbo life and decreases lag).
> Now, there is also a vacuum/pressure line that was hanging loose but seems
> to be intended to connect the BOV body to the intake manifold upstream of
> the BOV. This isn't what you are referring to, is it? I have thought
> this was simply a way for the BOV to determine, independently of any other
> inputs, when to open, but just leaving the spigot on the BOV open to
> atmosphere seems to work fairly well as well.
That's not what I'm referring to (if it's just a standard size vacuum
line). The recirculation hose is generally pretty good sized... That small
line is part of the system that helps the BOV determine at what pressure
level to open. Not as familiar with how that works because, well, it always
"just works"... Haven't had to learn about it :-) You obviously want the
BOV to open at just a psi or 2 above your peak boost level...
More information about the MR2