Mazda Wankel Engine - Displacement

Displacement

When Wankel engines became common place in motor sport events, this created the problem of correcting the representation of each engine's displacement as provided by the manufacturer, for the benefit of competition. Rather than force the majority of participants (driving piston engine cars) to half their quoted displacement (likely resulting in confusion), most racing organizations simply decided to double the quoted displacement of Wankel engines. For calculating taxes in Japan, the displacement of Wankel engines is defined as the equivalent of 1.5 times the nominal displacement, so the 1308 cc 13B engines are taxed as 1962 cc. Whereas the actual displacement is 3924cc if all cycles are counted during the 1080 degrees of crankshaft rotation. If a comparison to piston engines and the "accepted" norm must be made and "accepted" norm being a 4 stroke piston engine. All cylinders have completed their cycles within 720 degrees of crankshaft rotation, no matter if its a 4 cylinder, 6 cylinder or a V10. Since the 1080 degrees or 3 revolutions of the rotary crankshaft is 50% greater than the 4 stroke engine i.e. travelled 50% more distance, the 3924cc should be divided by 1.5 to bring it in line with the "accepted" 720 degrees or 2 crankshaft revolutions giving an engine displacement of 2616cc. This formula also works for two stroke engines where the cylinders have completed their cycles within 360 degrees of crankshaft rotation, the displacement would be doubled to bring it in line with the 720 degrees of crankshaft rotation of the four stroke cousin.