The benefit of mutual scavenging is that the length of tubing to make that
happen is shorter (by approx 1/2) than the self scavenging approach.  The
reason is there is approx 120 rotor degrees between two exhaust port
openings on one rotor, whereas there is only approx 60 deg rotor degrees
between port opens between the two rotors permitting a shorter tube to get
the timing right which is rpm dependent as well as exhaust gas temp
dependent.

FWIW

Ed

 

Let us open our Rotary Bibles, (Racing Beat Catalog) to Psalm (page) 23 and read:

 

For non-ported, street ported, or Bridge ported engines. Short system is 22 to 25 inches, Long system is 120 to 125 inches of tubing 1.7 to 1.8 ID.

 

For 600 to 650 Holleys, short system is 15 to 18 inches. The long system is 113 to 118 inches.

 

For Pport engines the short system is 10 to 18 inches and the long system is 89 to 94 inches with tubing ID of 1.9 to 2.0 inches.

 

I suggest that these numbers are measurements from actual successful race cars. The lengths for the long systems must include mufflers of some sort with exhaust ending beyond the rear bumper.

 

Typical systems had the collector and Mazda race muffler under the rear bumper.

 

So, probably, single pipes from each housing might work fine. (two pipes with a muffler on each) And might work fine in much shorter lengths. Scavenge wise. Un-muffled is out of the question.

 

Lynn E. Hanover