james coffman wrote:

I'm at the stage where I need to make a plenum or
dynamic chamber for the manifold. In Tracys book he is
showing his made with separate chambers for inner and
outer runners to utilize reflected waves from the
closing intake ports.  My engine will be
turbo-normalized.   Easiest construction would be a
cylinder with throttle body on the end.  How about a
discussion on construction of the plenum?  Thanks Jim
Coffman

The dynamic chamber is not what we need. It gives more torque at
3000 RPM at the expense of less HP at 6000 RPM. In effect it doubles
the length of the runners and that is why Mazda uses it to enhance
the torque at 3000 RPM. Low speed torque is a real problem with 
the rotary used in cars. The problem is the convoluted air passages
where the air enters the dynamic chamber. Best to use a simple
cylinder or square tube plenum with a simple three inch or larger
single butterfly throttle body facing forward picking up dynamic pressure 
and cold air. Don't forget the bell mouths where the runners enter the plenum.
Worth about 10 HP more around 190 to 200 HP.


Paul Lamar
 
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