Charles on Cars: An explosive story of rotary technology

When you think of German cars, you think of the BMW, Mercedes, and Porsche. What you probably don’t think about is Felix Wankel or his rotary engine. Wankle is a German man who never had an engineering degree or a driving license. Yet, he is the man that created the rotary engine, and he designed it as a teenager. He never really made an advancement in the engine, nd didn’t get to marketing it until after World War II.

A rotary engine is a combustion engine that works totally differently than an ordinary combustion engine. In a normal combustion engine the suck-in, bomb, and bow out are done with in a cylinder piston. The piston goes down, and the air and fuel come in. It goes up, and the air and fuel combust. It goes back down, and the exhaust escapes the piston.

In a rotary engine these stages are done by a bloated triangle (the sides are circular) within a pinched oval. As the three sides roll, they go through the three stages of combustion. In general, these engines are a lot less environmentally friendly than an average 4-cylinder, mostly because they use more gas, and their oil has to be changed every other fill up.

The reason why the engine is so famous is because even though it was smaller and not as good for the planet, the engine could get much larger horsepower numbers out of a smaller engine displacement. The engine also needs to be driven at the maximum RPM to keep the engine working well, and the oil at the right temperature. If you drive other engines too long at high RPMs, things start to break.

Wankle created his first usable design in 1951, while working for the NSU motorcycle manufacturer. NSU would invite leaders of the auto industry to see if they could sell or licence any of their engines.

Mazda, which until then was building small trucks, would be the company that would license the engine from NSU. Mazda put all their money into the engine after its CEO fell in love with its design. They would license the engine and send it back to Japan. Mazda gave the engine to their chief engineer and told him that it had to be reliable. Production began promptly.

However, the engine kept exploding. This was mostly because the tips of the triangle keep deteriorating on the sides of the engine. The problem could not be solved until the chief engineer had a “eureka!” moment while writing. He would replace the points of the triangles with graphite. These pieces of graphite are now called apex seals.

This adjustment launched the engine into production, and it made its first appearance in Mazda’s first car, the Cosmo sport 110. It would become the staple engine in RX7 and actually the only Rotary engine car Mazda sold after 1977.

After the RX7 was retired, the last car that had a rotary engine was the RX8, though it was nowhere near as good as the RX7. The car had problems with Apex seals and on rare occasions the engine would fail altogether. The RX8 was retired in 2012, and with it, the rotary engine.