[Diy_efi] Intro, and q's about fuel economy

[Bernd Felsche]

On Mon, Dec 16, 2002 at 04:10:49PM +0100, Alexei Pavlov wrote:
> > Using the valves to throttle the flow has different effects on the
> > flow. It's still throttling; i.e. restricting.

> > The main difference is that with variable lift, that the gas flow
> > speeds through the valves is higher and this results in greater
> > swirl and filling of the chamber.

> > Further; the flow upstream of the valve is unthrottled, so it's at
> > atmospheric pressure or greater, even when not supercharged. In
> > essence, the vacuum the piston has to draw is out of a smaller
> > volume; the cylinder itself instead of the whole inlet tract.
> > (A bit of a simplification, but it helps to draw the mental
> > picture.)

> I would say that pumping from a large volume is easier than
> from a small one. Am I wrong ?

The large volume in that case is planet Earth's atmosphere.

The effect is the same... the top of the inlet tracts is close to
atmospheric pressure (or possibly greater under benefical resonance)
which is usually higher than the pressure in a throttled inlet
manifold.

-- 
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