Quote:
Originally Posted by mad_sb
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).
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thanks for the help. i'm a bit confused though. if the crankcase vent goes back to the intake before the turbo, i agree that the air being
pushed out will be metered, but the air being
sucked in (which is the primary purpose of the crankcase vent, as the pcv has a check valve in it and will not allow air into the crankcase) will not be metered, and will eventually make it back into the intake manifold as unmetered charge. i noticed this from the idle/low fuel trims that we're going nuts. i've since capped the manifold to keep that unmetered air from getting back into the manifold and i have a far more stable idle (still have to log trims again, but i expect them to be improved).
so then is the idea that if i can get the crank vent tube to somewhere that is always under vacuum (in front of the turbo) it'll not pull in unmetered air? does this hold true at idle when there is very little vacuum in front of the turbo, or will a setup like this cause the same issues at idle/low-load as before?
thanks for all your help! this is driving me nuts trying to get it right lol.