PCV routing if MAP.

[94gsl5.0]

I know that if MAF base we need to have a closed PCV system. So as to keep the air metered, if not you run into a vaccum leak. Yet the problem people are having (especially when boosted) is oil vapor consumption. To help, a catch can is installed so they don't eat the vapors.

What if MAP based and boosted? If MAP, why can't you just vent the crank case to atmosphere? No "unmetered" air will be pulled through the breather since the ECU is using MAP to run the car. If the breather gets excessivly oily, use a catch can between the breather and crank case. This way no oil is taken up through the intake manifold and you run less of a chance boosting the crank case via the PCV line (some boost gets by even with 2 billion check valves on the thing and i would rather let what little gets by the pistons to vent rather than get bottled up by check valves). The line from the filler neck would still be routed to the intake piping to pull some vaccum. Is this a valid way to run things if MAP?

Any thoughts? Anyone running MAP based tunes please chime in...

 

[HISSIN50]

The big issues come from mixing PCV and breathers. Even on a MAF set-up, you should be able to run one or the other (not both) and be alright regarding the metered air issue.

To answer your question, on my SD (MAP) '88, I've run with breathers and it's fine. Just remember that in stock applications (not you - you're boosted) PCV actively pulls vapor out of the crankcase (good) whereas breathers are passive.

And really, if youre forced induction, you should have tuned with enough fudge factor that even if you did have some unmetered air, it would not be a big issue.

Random thoughts. Good luck.

 

[94gsl5.0]

thanks...

I am hoping that i can still pull some vapors outa the crankcase via the nipple on the filler and just vent the crank case to atmosphere. I'll try the catch can to breather setup and see how it does before the rain hits hard.

As for the tune... the tune is a bit on edge but the 02 feedback and IAT/timing tables takes care of the fudging, gotta love computers