What do you do then? I think the PCV is beneficial, but if you don't have a vacuum hook-up on the TB are you then pulling in un-metered air if you run it to a port on the plenum? Or is the PCV so minor the air is un-metered anyway?

PCV is a closed loop, and is metered. It connects typically to the intake plenum (on port EFI). The [upper] port on the throttle body is for the fresh air intake to complete the PCV loop. Perhaps this is what you're saying already, but just verifying. PCV valve (drivers side) connects to plenum vacuum source and draws vacuum on the crankcase which is fed by fresh air by the hose connecting the passenger side valve cover to the fresh air port on the throttle body (which is behind the mass air flow sensor and is thus metered).

I can't comment on what difference it might make on the MAF cars, as all I've dealt with is speed density. Would run a touch leaner I presume.

Thanks for the reply.

Yes so on the pass side, there is a line that goes to the TB and draws fresh air.

So that fresh air must be coming ahead of the TB (i.e. through the IAC passages maybe prior to the IAC valve to let air past the blades when the throttle is closed.)

I'm just trying to figure out, if you ran a TB that didn't have that port for the air, do you run a breather on the passenger valve cover and still run the PCV valve on the driver's side. Or can you run it to the plenum as well (I don't think so but...??)?

TIA

You just need filtered air. So either a breather or a line to the air intake (between the TB and the Air filter). Run the driver side as normal. You don't want to hook the pass side to the plenum because it will pull vacuum on the crank case essentially creating another "dirty side"

It would cause you to run richer becuase there is less clean air charge and it reduces combustion effeciency. Burning oil is bad.

The PCV is actually considered un-metered air because it enters past the throttle body, it is accounted for though in the computer/tune. If you have an open PCV that is why you get an erratic idle.

Are you saying running a breather/line to the air box would reduce efficiency/clean air charge/run richer or that running it to the plenum (no clean air) would do that.

(The not running it to another source of vacuum makes sense.)

Yeah, the car would has a custom tune, so I would think I can just adjust for the air pulled through the PCV-vacuum in the tune then.

Thanks.

You need a fresh air in on one side and the other side hooked to the manifold to pull vacuum on the crankcase. There has to be a clean air inlet for the PCV to work correctly. Running both sides to the plenum would be bad, that would possibly cause a rich condition. I was just meaning that if you are pulling oil in it will cause the car to run richer because of incomplete combustion.

Ahh, ok.

Cool, so a line to the air box or a breather shouldn't be a big deal then.

Thanks!