Similarities
Similar to a piston engine, the rotary engine is an internal combustion engine, which is driven by the explosion of a fuel/air mixture. It performs the same four stages as a piston engine such as intake, compression, combustion and exhaust, but unlike the piston engine each job has its own dedicated area specifically made for each of the four stages. The piston engine jerks back and forth a couple of times before it can successfully perform one full cycle. The rotary engine on the other hand does this and more per cycle and it only spins in one continuous direction, which means more power and efficient. A piston engine moves into two directions, which cause more friction and engine ware. The rotary engine turns in an epitrochoid similar to something you make using a Spiro graphs. The rotors are triangular shape so the fuel/ air mixture in the side of the housing and the faces of the rotor. While the rotor rotates around the epitrochoid chamber each volume of gas expands and contracts so that’s three explosions per revolution it take the piston engine much 4 time that long to produce the same power. The rotary engine contains no valves, intake or exhaust ports because each connect directly to their respective counter parts which ads to better efficiency and more power
Differences
The rotary engine had fewer moving parts compared to the 40 plus parts such as timing gears, crankshafts, rockers, timing belt, valve springs, camshafts, valves, pistons and connecting rods which are typical in a typical piston engine. A rotary engine is internally balanced and runs much smoother because it spins in a single direction instead of the jerking back and forth motion of a piston motor. The RCE Rotor supercedes the piston engine's reciprocating piston. The RCE Eccentric Shaft [gloss] supercedes the piston engine's crankshaft and connecting rods. The RCE Peripheral Housing [gloss] supercedes the piston engine's cylinder. Intake and Exhaust Ports [gloss] in the housings eliminate valves, camshafts, cams, lifter rods, and timing belts. See also porting.
Advantages and Disadvantages
Advantages Light weight and compact. Smooth: no reciprocating motion. Extended power "stroke" rotation of the output shaft: 270 degrees vs. the 180 degrees of a piston. Fewer moving parts: no valves, connecting rods, cams, timing chains. Intake and exhaust timing are accomplished directly by the motion of the rotor. Flat torque curve because no valves are used. Cooler combustion means fewer oxides of nitrogen. Catalytic converters lessen this advantage. Separation of combustion region from intake region is good for hydrogen fuel. Lower oxides of nitrogen (NOx) emissions.
Disadvantages High surface to volume ratio in combustion chamber is less thermodynamically efficient. The Wankel's long and narrow chamber makes for long flame travel, but this is countered by the Mazda's two spark plugs (three on some racing engines). Higher fuel consumption in naive designs. This is relative to the application because the high power of the engine must be considered. Thus Mazda has been successful with the RX-7 sports car, where its fuel economy is comparable to other cars in its class. Only 16 years after the first engine ran, the 1973 oil crisis devastated the RCE before it had sufficiently developed to become more economical. Thus the engine has a more negative reputation regarding fuel consumption than is actually deserved. Higher carbon monoxide (CO) emissions in naive designs.
