Anti-reversionary step - how does it work?

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Mon, 8 Jun 1998, Kevin Ford wrote:

> The resulting low pressure area that is formed as the pulse passes by 
> will help to scavenge the cylinder.

I don't see this happening very much at all in a turbo because the cam 
reduces overlap to a very low level.  Does anyone have the exact number 
of degrees of overlap on the turbo cam?

> A reflected pulse (echo) will not scavenge, it will impede the fresh 
> charge's progress into the cylinder.  The antireversionary step will 
> help lessen the reflected pulse, thus lessen the impedence on the fresh 
> charge's entry into the cylinder.  

A million people have told me this.   What I want to know is _how_ it does 
that, and then if you can persuade me that it is true, how big does that 
step have to be.  We're talkin' turbos only here too BTW.  Lets not loose 
our focus.

> In 2 stroke engines, it is quite common to use a tuned exhaust pipe.  

Yes, I understand 2-strokes.   I have the formulas to design expansion 
chambers, and mostly understand how that works.  Lets not confuse the 
turbo issue with 2-stroke stuff unless there's a specific point to be made.

Later,
Graydon D. Stuckey

"There's alot more to Jazz than just wrong notes"