rookie7

by the way, there is no centripetal force acting on a piston. the piston has linear motion not a circular motion. and of course there is work produced by a piston, where do you think horsepower comes from??
power = work/time

rookie7

by the way, there is no centripetal force acting on a piston. the piston has linear motion not a circular motion. and of course there is work produced by a piston, where do you think horsepower comes from??
power = work/time

Orange!FD

bzzzt! No cigar for you either, rookie7. What you're saying is that the percentage of the revolution (crank/eccentric) during which the combustion products are pushing on the rotor/piston is all-important in determining power output. Why do you think that? What does the duration of the power "pulse", or the percentage of a rev that it occupies, have to do with power output, assuming a constant amount of fuel/air is burned? Nothing.

If anything, I would expect a longer power pulse to allow the combustion products a greater opportunity to lose heat to the engine surfaces, decreasing their pressure and hence, efficiency.

peejay

The longer power pulse is why the engines are so smooth, though. A longer, softer push.

rookie7

That's where you're wrong OrangeFD, it is not "a constant amount of fuel/air", the power cycle of a 1.3L 4 cylinder engine uses the volume of 1 cylinder,that is 1.3L/4 = 325cc while the rotary power cycle uses the volume of 1 chamber which is 1.3L/2 = 654cc. In other words, in 2 revolutions a piston engine will have 4 power cycles of 325cc each cylinder pumping out 1.3L, while a rotary will have 4 power cycles using 654cc for each rotor pumping out 2.6L.

On top of that you have the rotary engine power cycle lasting 90 degrees of eccentric/crankshaft longer than that of a piston engine. That means you apply a force over a longer distance which translates into more work produced by the rotary which means more power.

peejay

So far so good...
This is where the snag is. Yes the power pulse lasts 50% longer, however that doesn't mean 50% more work done. Remember, there is only so much air and fuel in the chamber, and there is only so much power that can be exctracted from it. It works out to be roughly the same amount of "push" (power), just spread out over a longer time. I say roughly, because in fact less power is actually harnessed, due to various thermal problems mentioned previously.

It's actually beneficial that the burn is 50% longer, because the chamber is so inefficient it takes forever to propagate. That's why, even with a 50% longer burn, it's STILL burning as it exits the exhaust port.