[MR2] <MKIIT> BAD BOV!!

[Brian Knoblauch]

> 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 
> idea
> 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 
air/fuel ratio.

    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 
> that
> 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...