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Originally Posted by compnut21
why bother with the catch can at all? keep oil from dripping around the engine bay or emissions were my only guesses.
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Yeah, that's right, they make a hell of a mess if you make much power ;-) The article is kinda targeted at the 150hp/litre UP mark, so not something you would see on may f2t setups. The stock setup for the f2t is probably fairly adequate with a catch can added inline and left more or less as is.
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also is there a better brand/type of pcv valve that can be used? maybe one that seals well under boost or something of the like?
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As I tried to indicate in the article, I don't believe the "my PCV valve sucks" hype if it is A clean and B genuine Mazda. The miata crowd are dead set on GTX PCV valves, and I've seen many references to the starion ones over the years too. I have a stock FE3 one on my engine and in 200kkm old stock condition too. I'm not concerned about that aspect at all.
What I AM concerned about is the total lack of flow OUT of the crank case through the breather. As Rob has shown above there is an absolute need to modify this with higher output. My only personal evidence is the oil I found in my bay quite far from the exit of the hose that had traveled horizontally indicating significant velocity and therefore much too small an orifice.
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but why not incorporate something in the intake tract to create vacuum no matter what condition?
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The main reason is that there is umpteen times more exhaust gas flowing, so the speed is much higher and the effect much more. Secondly a slight restriction in the exhaust is MUCH better than the same restriction in the intake. Lastly, the only part of the intake with active flow is under boost pressure.
However, what you describe is pretty much what OEMs do. The tube to the intake stock is under slight vacuum from the air filter restriction and draws gas out that way.
Fred.
8-6-08, 4:25
