Larry Widmer's "Soft head" swirl technology

[Andrew W. Macfadyen]

Swirl is a general Fluid-Dynamic term used in all sorts of flow situations
it was first used in connection with combustion chamber design way back
around the time of WW1, certainly Sir Harry Ricardo used to describe  both
the rotational flow induced by the inlet port design and that induced within
the cylinder by "squish".
The term "tumble-swirl" has been used to describe the flow in modern narrow
valve included angle engines in several technical publications and is quite
descriptive of the type of flow however I have until now never seen   term
tumble used on its own for this type of flow. All that the combustion
process sees is the degree of mixing it cares not wether it is swirl or
tumble-swirl or squish.
Just how big a difference it can make was underlined to me about 20 years
back while racing 1000 saloon cars and I saw just how much adavance (43
crank deg) the Coventry-Climax inspired  Rootes/Chrysler Imp engine required
compared to the  Cosworth-Ford  MAE engine.

Dave Williams wrote:

> -> the first engines to use a narrow valve included angle  to induce
> -> swirl about a horizontal axis parrallel to the crankshaft. Because of
>
>  Normally (at least on this side of the pond) "swirl" refers to motion
> parallel to the cylinder axis; "tumble" refers to motion parallel to the
> crankshaft axis.
>
>  Narrow-included-angle four valve heads are usually very good at tumble
> and poor at swirl unless something is done with the valve timing or
> shape of one of the intake ports.  Some engines use valves or deflectors
> of various sorts in one port to induce swirl.
>
> ==dave.williams at chaos.lrk.ar.us======================================
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