All Mazda rx7 engines are essentially a single family — they all derive from the first Wankel experiments in the early 1960s. Over the years, displacement has been increased (somewhat), and turbocharging has been added to great effect.

In auto racing, the displacement of  Wankel engines is usually doubled for classing purposes. For Japanese tax purposes, the displacement of rx7 engines is defined as the equivalent of 1.5 times the nominal displacement. So the 1.3 L 13B engines count as just under 2.0 L for these purposes.

Wankel engines can be classified by their rotor size in terms of width (diameter) and depth (thickness). These metrics function similarly to the bore and stroke measurements of piston engines. Nearly all Mazda production Wankel engines share a single rotor diameter: 105 mm (4.1 in) with a 15 mm (0.6 in) cankshaft offset. The only engine to diverge from this formula was the rare 13A, which used a 120 mm (4.7 in) diameter and 17.5 mm (0.7 in) offset.

This engine is starting to become popular with kit car builders, hot rodders and in light aircraft because of its light weight, compact size and tuning potential stemming from its inherently high power to weight ratio[citation needed].

40A

The first RX7 engines was the 40A, a single-rotor engine very much like the NSU KKM400. Although never produced in volume, the 40A engines were a valuable testbed for Mazda engineers, and quickly demonstrated two serious challenges to the feasibility of the design: "chatter marks" in the housing, and heavy oil consumption. The chatter marks, nicknamed "devil's fingernails", were caused by the tip-seal vibrating at its natural frequency. The oil consumption problem was addressed with heat-resistant rubber oil seals at the sides of the rotors. These early engines had a rotor diameter of 90 mm (3.5 in), an offset of 14 mm (0.6 in), and a depth of 59 mm (2.3 in).

L8A

The very first Mazda Cosmo prototype used a 798 cc L8A two-rotor Wankel. The engines and car were both shown at the 1963 Tokyo Motor Show. Hollow cast iron apex seals reduced vibration by changing their resonance frequency and thus eliminated chatter marks. It used dry-sump lubrication. Rotor diameter was up from the 40A to 98 mm (3.9 in), but depth dropped to 56 mm (2.2 in).

One-, three-, and four-rotor engines of the L8A were also created for experimentation.

10A

The 10A series engines were Mazda's first production Wankel engines, appearing in 1965. It was a two-rotor design, with each displacing 491 cc for a total of 982 cc. These engines featured the mainstream rotor dimensions with a 60 mm (2.4 in) depth.

The rotor housing was made of sand-cast aluminum plated with chrome, while the aluminum sides were sprayed with molten carbon steel for strength. Cast iron was used for the rotors themselves, and their eccentric shafts were of expensive chrome-molybdenum steel. The addition of aluminum/carbon apex seals addressed the chatter mark problem.