National agencies that tax automobiles according to displacement and regulatory bodies in automobile racing use a variety of equivalency factors to compare Wankel engines to four-stroke piston engines. Greece, for instance, taxed cars based on the working chamber volume (the face of one rotor), multiplied by the number of rotors, lowering the cost of ownership. Japan did the same, but applied an equivalency factor of 1.5, making Mazda's 13B engine fit just under the 2-liter tax limit. FIA used an equivalency factor of 1.8 but later increased it to 2.0, using the displacement formula described by Bensinger.
