Intermittent crankcase pressure issues
Fair point. I'll be honest I'm not even really sure what purpose that fulfills. I saw the diagram but what does that hose do that a breather and pcv doesn't? I know there's no significant vacuum at WOT so the PCV isn't as effective but wouldn't that be the same case at the air cleaner?
Well, actually there is TONS of vacuum at WOT, just not where YOU'RE thinking. Engine vacuum falls off on acceleration, yes, but vacuum increases severely at the air cleaner going into the engine. That's the other half of the PVC system. When one side falls off, the other side reverses flow into the engine intake pulling the crankcase gasses in through the air cleaner on the other side. This is why often times when you leave the breather disconnected from the air cleaner, you get oil all over the valve cover. That same oil mist can also over come the rings at high RPM and get blown out through the combustion chamber.
The PCV system works good only TWO ways. 100% complete, OR 100% eliminated. I like the system, because on a street car, it actually helps keep the rings sealed and keeps oil consumption down.
On the older cars (mid 60s and prior) they used "OCV" or open crankcase ventilation, which had what was called a road draft tube that stuck straight down into the air flow under the car. All it did was dump the crankcase vapors right into the atmosphere. At least with the PCV, not only are those vapors burned, but an active vacuum is put on the crankcase, helping to keep rings sealed. It's really a win/win.
Yes, people have run "only this" or "only that" for like ten thousand years and "never had a problem", but how would they know the difference if that system had never been complete?
