Ed wrote:
>...silly questions... MY turn! MY turn!!
> Could someone please explain to me
>just what the function of the PCV -valve-
>is? Why is a 'valve' needed?
> I understand that the purpose is to pull
>crankcase vapors back thru the intake to
>be burned with the fuel charge; but, why
>do we need this valve? Why not just an
>open hose from the crankcase vent to
>the air cleaner?
> Thanks
Ed, no question that I can answer is silly.
(-8 It's my opportunity to contribute to the list, so allow me to
educate you on my understanding of how/why the PCV valve works--
At idle and at low speeds, manifold vacuum is high, and very few
crankcase vapors are produced. Only a low flow through the PCV valve
helps keep the crankcase clean, so the PCV valve is kept nearly closed
by the high vacuum. High airflow (as you would get with just an open
hose) through the system at idle and at low speeds would lean the
air/fuel mixture, causing poor performance.
As the throttle is opened and engine speed increases, blow-by increases
and the manifold vacuum decreases. Less vacuum opens the PCV valve to
allow more crankcase ventilation.
Basically, the PCV valve adjusts the amount of air flow/crankcase vapors
entering the manifold by adjusting to the manifold vacuum. You don't
have this ability if you used a plain hose, and driveability would be
affected (it'll run like sh*t).
Does all that make sense?
-NORY
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