How a Wankel Rotary Engine Works, and the Best Models of One

How a Wankel Engine Works

The housing. The inside of the housing has a shape called an epitrochoid: an oval pinched in at the waist on both sides. It is the path the rotor's three tips trace as it turns, so the tips stay in contact with the wall all the way round.

The rotor. The rotor is a triangle with curved sides. Each tip carries an apex seal that slides along the housing wall, and the three sides of the rotor divide the housing into three separate chambers. As the rotor turns, each chamber grows and shrinks twice per revolution.

The four strokes. Follow one chamber round the diagram. As it passes the intake port, its volume grows and it draws in air and fuel. Moving over the top, it shrinks, compressing the charge against the waist where the spark plugs sit. The plugs fire, the burning gas pushes on the rotor face, and the chamber grows again as it travels round the bottom. That is the power stroke. Finally, it reaches the exhaust port and shrinks to push the burnt gas out. All four strokes happen at once, one in each chamber, at any moment.

The shaft and gears. The rotor does not turn on the centre of the shaft. It rides on an eccentric lobe, so its centre moves in a small circle. An internal gear in the rotor rolls round a fixed gear on the housing with a ratio of 3:2, which keeps the tips on the wall and makes the shaft turn three times for every turn of the rotor. Each of the three rotor faces fires once per rotor turn, so the shaft gets one power stroke per revolution from every rotor.

Why It Is Different From a Piston Engine

What it does well. A Wankel has very few moving parts: in essence the rotors and a single eccentric shaft. Nothing changes direction, so it runs smoothly and revs freely, and it is compact and light for its power. That is why Mazda put it in sports cars.

What it does badly. The combustion chamber is long and thin and moves as it burns, which costs fuel and makes clean exhaust hard to achieve. The apex seals are the weak point: they wear, and when they fail the engine loses compression. And because the seals need lubrication, a Wankel injects a little oil into the housing and burns it by design.

A Short History

Felix Wankel developed the engine with NSU in Germany, and the first one ran in 1957. NSU put it into production in the Wankel Spider in 1964 and the Ro 80 saloon in 1967. Mazda launched the Cosmo Sport the same year and carried the rotary through the RX-7 and RX-8, and a Mazda 787B won the 24 Hours of Le Mans in 1991, the only win there for a rotary engine. The RX-8 went out of production in 2012. Mazda brought the rotary back in 2023, not to drive the wheels but as a generator in the MX-30 R-EV.

Choosing a Wankel Model

To understand how it works: the EISCO cutaway. You turn it yourself, slowly, and the lamp shows the firing point, which is exactly what you need to follow the cycle in the diagram above.

To build one: the Mould King brick kit, at 2,177 pieces, or the metal Wankel model for a smaller, quicker build in metal.

For a classroom: the 3B Scientific transparent model, made to be projected.

What About a Wankel That Really Runs?

Miniature rotary engines that burn fuel exist. Toyan makes the RS-S100, a single-rotor engine, and the RS-L200, a water-cooled twin-rotor of 4.92 cc. On October 1, 2026, both were sold out at every retailer we checked: Stirlingkit, Enginediy and Nikolatoy. We will add them here when they are back. Until then, for engines that burn fuel, see our best real working model engines and the Toyan engines guide.

More Engines to Explore

• Car engines in every layout: best visible engine model kits, best V8 engine model kits and best V12 engine model kits.
• Brick-built engines: best building block engine kits.
• Every kit we cover, in one searchable table: the model engine kit database.

What We Could Not Verify

We have not built these models. Their specifications come from the makers and the retailers that sell them:

• The EISCO model was checked against Eisco Labs' own product data on October 1, 2026.
• The metal Wankel model was checked against Enginediy's product data the same day. The listing does not say whether it is motorised.
• Amazon listings could not be read on October 1, 2026. We confirmed the Mould King and 3B Scientific models by their Amazon listing titles in search results, and took the 3B Scientific details from the maker. Check the live price and availability on each card.
• The Mould King kit's build time, size and age rating are not given in the sources we could read.