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Re: SVO - svo Digest - V01 #50
On Tue, 9 Dec 1997, Brian Knowles wrote:
> I'd been thinking that with a cam on a blown engine, that the idea was to
> open wide and early, blow it as full as possible, touch it off, repeat
> Youl'd want little overlap, and increases in performance would be thru
> more volume/pressure (bigger, badder blowers) or increasing RPM. Cam
> timing wouldn't be real agressive here, 'cause cylinder filling would be
> more a function of manifold pressure than intake tract resonance, so open
> early and close the exhaust early. Is this the right track, or am I
> making some fundamental mistake here?
Only in that turbo motors and blower motors are completely different
On a turbo motor, you have to keep in mind that under boost, the exhaust
manifold pressure is roughly *double* the intake pressure, while with a
blown motor, it's the same as with a normally-aspirated motor. The back
pressure comes from the turbo, not from the manifold, and the more boost
you run, the higher it goes.
That's why I think that the exhaust timing is more important than the
intake timing -- you need to effectively clear the cylinder of the spent
charge, but as long as you're "in the ballpark" with the intake, it's not
gonna make a big difference -- that's what the pump is for.
got some new mail...:)
Talk to you later,