madaz matt

I ve been reasherching expantion chmbers and now i have a good grasp of the concept so why not on rotaries an expanchon chamber on a 2-stroke dobles power and since rotas have ports like 2-strokes woldet this help make alot more power n/a of corse, space restrictions mabe.

Lynn E. Hanover

The thinking is good. The rotary is a 4 Otto cycle engine that tunes like a 2 Otto cycle engine.



The trick you are looking to duplicate is to have a huge amount of overlap, where a large amount of the intake charge is over scavenged, (started out through the exhaust port) and before that port closes is shoved back in by a reflected wave from inside the tuned chamber.



So the tuned ram effect from the inlet tract is over charging the cylinder and the exhaust is overcharging the cylinder from the chamber side as though there were two supercharged inlet tracts.



Some of the perameters required to make this work are:



Very short distance between bypass porting and exhaust port.



Long overlap periods (intake and exhaust open at the same time)



Small diameter induction and exhaust tubing to develop the high velocities needed to make this work.



Better performance at very high revolutions (above 10,000 RPM)



The rotary is blessed with a good distance between intake and exhaust ports.

The rotary requires extensive modification to operate at RPM where this becomes productive.

The induction and exhaust tube diameters cause tuning lengths to be longer and operated at lower frequencies than a dirt bike or Kart engine.



For rotaries that are to operated at high RPM all of their lives, the idea is used to some advantage.

I have not read where there was an attempt to reverse flow the exhaust to any advantage, but precise tuned lengths for the primary lengths and diameters and good collector design do make a huge difference in power output. Here the effort is to make a good long lasting (wide power band) low pressure area at the exhaust port so as to get the slugish inlet charge moving as soon as the inlet port opens.



So we do that on the inlet side now in stock and racing forms. But not on the exhaust side where we are looking for the lowest pressure possible at the port.



Lynn E. Hanover

Hyper4mance2k

What about in perifrial port applications? Huge over lap and high rev range.

Lynn E. Hanover

Well, it sounds right.



But the actual overlap is lower than a "J" bridgeport.



From Paul Yaws site



www.yawpower.com



The "J" port opens the intake at 115 BTDC and closes it at 72 ABDC.



The factory Periphery port opens at 86 BTDC and closes at 75 ABDC.



If there were to be some reaserch on the subject, then the Pport would be the one to work on.

The possible flow at even small angular opening is very large, so any effect will be obvious.



The distance between the ports and the long tuned columns involved, in my mind preclude any benifit in the reflected wave tuning. Most builders are looking for a 3" minimum exhaust system. Daryl Drummmond specifies a 4" system (what I have). The reason is the minimum possible back pressure, and the maximum possible low pressure in the exhaust port.



I would be happy to be completely wrong on this point. More power for us all. But I don't think so.





Lynn E. Hanover