Miata Turbo Forum - Boost cars, acquire cats.

Quote:

Originally Posted by BogusSVO (Post 966606)

The Stock 4G63T PCV System

So far we’ve mostly talked about the PCV system as it applies to naturally aspirated gas engines. These same principles apply to our turbo DSM’s, with a twist. In a turbocharged engine, the IM can see positive pressure as well as vacuum, so the PCV system takes on another role. Not only is it responsible for ventilating the crankcase with fresh air while the IM is in vacuum, it also has to relieve the crankcase of excessive pressure buildup during boost. Because of this, parts of the system must allow air to flow in two directions while preventing it from flowing in a certain direction under different operating conditions.

Hi Bogus,

Excellent writeup, made alot of sense, and cleared up alot of misconceptions and also confirmed my own inferences.

i have but 1 question with regard to the above paragraph quoted from you.

Are you saying that the same PCV is now changing in function and asumming a dual role function OR are we talking about 2 entirely different PCV valves? 1 for NA 1 for Forced Induction(FI)

1. NA PCV - During Decel or Idle, Vacuum in the IM is high, PCV v/v is closed and under load when vacuum is decreased, PCV v/v is open

2. "Twisted" FI PCV - When IM is in Vacuum, PCV is open, allowing ventilation and closed under boost when zero vacuum conditions in IM.

Many thanks in advance for you help.