Quote:
Originally Posted by jamesm
i've been working on getting my pcv system fixed up lately, first fixing a problem with the pcv leaking under boost and now trying to eliminate a vacuum leak.
the problem is that there is nowhere to run the crankcase breather to (the line that would normally run to the intake, not the pcv line running to the intake manifold). with a blowthrough maf, if i place the line before the turbo in the intake tract it's going to be pulling vacuum, but it'll also be pulling in unmetered air at idle/low load. i can't place it after the maf because that would be after the turbo, and would see boost.
my current plan is to just cap the intake manifold and run both the pcv and crankcase breather to a vented catch can. that way there is unmetered air in the crankcase, but at least it has no path back into the intake manifold. of course this produces little to no crankcase vacuum which kind of takes the 'positive' out of 'positive crankcase ventilation', but it seems like the best i can do.
how is everyone else handling this with a blow-through maf?
|
EDIT... I don't understand what your saying, if the maf is in blow through mode it is between the turbo and the throttlebody and the intake port would be pre turbo so it WOULD NOT be sucking in unmetered air at all since the air has yet to pass the maf at that point. If your worried about fuel trims, get some logs before hooking it up and after to compair, but i really don't think it will be an issue at all.
Your plan would never pull a vacuum on the case (as you mentioned). As an alternative, install a check valve between the manifold and can then tie the two crank case ports to the other side of the can. At least then it is pulling vacuum when off boost and the check valve closes under boost so the crank case would be vented to atmosphere under boost.
The best solution is to run two cans in the factory configuretation but with the intake port moved pre turbo / SC. Its a good idea to install a check valve between the manifold and can since the PCV will leak some under boost and was not designed for boosted applications. This way you have a vacume on the case all the time (intake side under boost, manifold side under vacuum).