Wankel rotary engine and piston engine displacement, and corresponding power, output can more accurately be compared by displacement per revolution of the eccentric shaft. A calculation of this form dictates that a two-rotor Wankel displacing 654 cc per face will have a displacement of 1.3 liters per every rotation of the eccentric shaft (only two total faces, one face per rotor going through a full power stroke) and 2.6 liters after two revolutions (four total faces, two faces per rotor going through a full power stroke). The results are directly comparable to a 2.6-liter piston engine with an even number of cylinders in a conventional firing order, which will likewise displace 1.3 liters through its power stroke after one revolution of the mainshaft, and 2.6 liters through its power strokes after two revolutions of the mainshaft. A Wankel rotary engine is still a four-cycle engine, and pumping losses from non-power strokes still apply, but the absence of throttling valves and a 50% longer stroke duration result in a significantly lower pumping loss compared to a four-stroke reciprocating piston engine. Measuring a Wankel rotary engine in this way more accurately explains its specific output, because the volume of its air fuel mixture put through a complete power stroke per revolution is directly responsible for torque, and thus the power produced.