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

[Alexei Pavlov]

bernie at innovative.iinet.net.au wrote:
> 
> 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.

So where is the gain on pumping losses ? Opening a little more the
throttle gives the same effect as removing the throttle and using
variable lift.

I understand the benefit of higher swirl.

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