RX8 Rotary Engine

[Dippy]

I was just reading Mazda's website and came across the following:

Higher power
A rotary engine’s power delivery is smoother. Because each combustion event lasts through 90 degrees of the rotor's rotation, and the output shaft spins three revolutions for each revolution of the rotor, therefore each combustion event lasts through 270 degrees of the output shaft's rotation. This means that a single-rotor engine delivers power for three-quarters of each revolution of the output shaft. Compared to a single cylinder piston engine, in which power is delievered to only a quarter of each revolution of the output shaft.

To me this seems to be patently untrue. Surely the torque occurs for 270 degrees of the 1080 degree cycle?

[JohnW]

Thats all complete bo!!ox.

okay so the output shaft is geared to turn 3 times as fast as the rotor shaft. If one combustion lasts for 90 degrees of the rotor, you need 4 combustion events equally spaced to give a 360 degree power cycle.

What they describe would be power at the output shaft for 270 degrees (3 x 90) followed by 810 without power (3 x 270)

Clearly the rotary engine has several combustions (between 4 and 8 depending on engine design) to give an even power spread across the cycle.
A 4 cylinder in line engine also achieves this. If you use a 6 cylinder engine with the correct V angle then you get 6 equally spaced combustion phases.

As you say they are talking rubbish, and comparing the engine designs in that way is not realistic.

Cheers,
John.