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Old 10-16-2013, 12:22 PM   #8 (permalink)
Occasionally6
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Quote:
Originally Posted by jeff88 View Post
Thanks serialk11r! After rereading this I was wondering what a 100% vacuum in the cylinder means for PCV (i.e. does it even need one, or would it actually increase crankcase pressure?)


Is this what you are talking about with the PV diagrams? (I've never actually seen this before.) Are you saying that with Valvematic, the PV "rectangle" will be flat rather than slightly curved?

Yes, that's a PV diagram but it's only for the working strokes; compression and power strokes. The area described by those lines is the work done by those strokes. (Check: the units of P x V are those of work.)

What's missing is the pumping strokes; inlet and exhaust. They form (ideally) a rectangle that is described by the inlet and exhaust manifold pressures and the volumes at the top (same as 1,2) and bottom (same as 3,4) the strokes.

That is also work but work the engine has to do. It has to be subtracted from the working stroke work (!) to get the net work out.

Lower inlet manifold pressures i.e. light engine loads and throttling increase the area of the pumping work. That also moves the working loop down (all the pressures are reduced) but doesn't alter its shape.
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