No pistons, no valves, no crankshaft. A rotary engine makes power with a rounded triangle spinning inside an oval, and Mazda has kept it alive from the 1967 Cosmo Sport to a rotor that now works as a generator.
The short answer
A rotary, or Wankel, engine replaces pistons with a triangular rotor that orbits inside an oval-shaped housing. Each of the rotor's three faces forms its own sealed chamber, and the four-step cycle (intake, compression, combustion, exhaust) runs in all three chambers at once. It is compact, light and smooth, but it burns oil, uses more fuel and wears its seals.
How does a rotary engine work?
The rotor is a triangle with bowed sides. Haynes calls the housing's shape an epitrochoid: an oval pinched in at the middle. As the rotor turns, the space between each face and the housing keeps growing and shrinking.
As a chamber shrinks, it squeezes the fuel-air mix. The housing has four zones, one for each step of the cycle, and each chamber works through the four steps in turn. The rotor itself uncovers and closes the intake and exhaust ports as it passes, so no valves are needed.
The rotor rides on an eccentric shaft, the rotary's version of a crankshaft. That shaft turns three times for every turn of the rotor, and each turn of the rotor delivers three power strokes.
Why use a rotary engine?
It is small and light. Mazda said its RENESIS engine was about 60 percent smaller than a V-6 of similar power and 40 percent smaller than a four-cylinder.
It is simple. Haynes counts three main moving parts and no pistons or valves.
It is smooth and loves revs. SlashGear says early rotaries ran with little to no vibration and calls the design happy at high rpm.
What are the downsides?
Apex seals. The tips of the rotor carry seals that keep each chamber closed off. SlashGear says that once they wear, they stop sealing against the wall, and Car Throttle notes that replacing them means opening up the engine.
Oil burning. A rotary injects oil to lubricate those seals, and that oil burns along with the fuel. Car Throttle says it burns oil by design.
Fuel and emissions. Car Throttle says the long, oddly shaped combustion chamber makes it less thermally efficient than a piston engine. Haynes says rotaries use more fuel than piston engines, and their emissions struggle to meet today's rules.
Torque. Autocar lists low torque alongside poor fuel use.
Where did the rotary come from?
Felix Wankel worked on the idea with German carmaker NSU from the early 1950s, and NSU first ran one on its test bench in 1957. Audi says the NSU Wankel Spider was the first production car with a single-rotor engine, on sale from fall 1964. The NSU Ro 80 followed, and in 1967 it became the first German car named Car of the Year.
How has Mazda used the rotary?
From Mazda's own pages:
| Year | Milestone |
|---|---|
| 1961 | Mazda licenses the rotary from NSU and Wankel |
| 1967 | Cosmo Sport (110S), Mazda's first rotary car, goes on sale |
| 1978 | RX-7 launches |
| 1991 | The 787B, with the four-rotor R26B, wins Le Mans |
| 2003 | RX-8 launches; RENESIS is International Engine of the Year |
| 2012 | RX-8 production ends |
| 2023 | MX-30 e-Skyactiv R-EV production starts, rotary as a generator |
The 787B is still the only rotary car to win Le Mans outright, and it made Mazda the first Japanese manufacturer to win there. Mazda has built more than two million rotary vehicles.
In the MX-30 R-EV, the 830 cc single-rotor engine (type 8C) only makes electricity, and the car is always driven by its motor. Mazda UK notes the registration lists 1660 cc, because EU rules count a Wankel at double its size. Mazda has also re-formed a 36-engineer rotary group and shown the Iconic SP concept, a two-rotor rotary EV listed at 370 PS.
On the street
A rotary rewards owners who learn its habits. Watch the oil, let it warm up before you shut it off (Car Throttle and PistonHeads both warn that a cold start followed by a quick shutdown can flood an RX-8), and budget for apex seals on a high-mileage RX-7 or RX-8.
FAQ
Is a rotary engine the same as a Wankel engine?
Yes. In cars, "rotary" means the Wankel design, named after Felix Wankel.
Does Mazda still make a rotary?
Yes. Mazda restarted rotary production in 2023 for the MX-30 e-Skyactiv R-EV, where it works as a generator.
Sources
- What is a rotary engine and how does it work? (Haynes), read 2026-11-12
- How does a rotary engine work? (Top Gear), read 2026-11-12
- How a rotary Wankel engine works (How a Car Works), read 2026-11-12
- Mazda's iconic rotary engine explained (SlashGear), read 2026-11-12
- Why rotary apex seals have a bad reputation (SlashGear), read 2026-11-12
- Rotary engines: how do they work? (Car Throttle), read 2026-11-12
- Engineering explained: why the rotary engine had to die (Car Throttle), read 2026-11-12
- 7 things you need to know before buying a Mazda RX-8 (Car Throttle), read 2026-11-12
- Mazda RX-8 buying guide: powertrain (PistonHeads), read 2026-11-12
- Understanding the bizarre workings of rotary engines (Autocar), read 2026-11-12
- NSU and the Audi Neckarsulm site, 150 years (Audi MediaCenter), read 2026-11-12
- The NSU/Wankel Spider (Audi), read 2026-11-12
- Rotary engines and oil changes (SlashGear), read 2026-11-12
- RENESIS named International Engine of the Year 2003 (Mazda newsroom), read 2026-11-12
- 2004 Mazda RX-8 (Mazda USA newsroom), read 2026-11-12
- Mazda celebrates 50th anniversary of its rotary engine (Mazda Canada), read 2026-11-12
- Rotary engine 40th anniversary (Mazda newsroom), read 2026-11-12
- Rotary vehicle production passes two million units (Mazda newsroom), read 2026-11-12
- RX-7 Heaven (Mazda USA), read 2026-11-12
- Mazda 787B and Le Mans (Mazda newsroom), read 2026-11-12
- Mazda reveals MX-30 e-Skyactiv R-EV (Mazda newsroom), read 2026-11-12
- MX-30 R-EV specifications (Mazda UK), read 2026-11-12
- Mazda Iconic SP (Mazda newsroom), read 2026-11-12
- Mazda reinstates its RE development group (Mazda newsroom), read 2026-11-12