Yeah, I know the feeling.
Anyway, I wonder about a couple of things. I think the trailing cylinder will receive less mixture and do less work than the leading cylinder.
When the leading piston is about to close its transfer ports, the trailing piston is still moving downward, increasing the scavenging pressure in your common crankcase. But by the time the trailing piston closes its transfer ports, the leading piston will already have moved up quite a bit, noticeably lowering the crankcase pressure.
And to what extent will your scavenging depend on exhaust suction? A tuned exhaust needs strong primary pulses. Exhaust
ports can provide these, because they open with a speed of about 1,5 x mean piston velocity. But exhaust
valves, as shown in your drawing below, can't, because they open with an initial speed of zero.
Exhaust valves will also make it difficult to achieve sufficient blowdown time.area, unless you plan to stick to really low rpm numbers. But that would mean a low power-to-weight ratio, which is not desirable, especially not in a light aircraft engine.
Attachment 333083
Bookmarks