Episode Details

The internal combustion engine, for all its mechanical sophistication, still runs on a 19th-century mechanical idea: pistons rising and falling, a crankshaft spinning, a steam-age architecture repurposed for gasoline and diesel. Every engine from Henry Ford's era right through to modern direct-injection and forced induction is fundamentally a variation on that same theme. So when a small Japanese company called Mazda introduced the Cosmo Sport in 1967, it wasn't just a new car. It was introducing a genuinely new kind of engine, one that didn't share a single conceptual bone with anything that had come before it.

The Triangle That Changed Everything

The engine in question was the Wankel rotary, named after German engineer Felix Wankel, who first patented the concept in 1929. Instead of pistons moving back and forth, the rotary engine used a triangular rotor spinning inside an oval combustion chamber. Its triangular shape allows intake, combustion, and exhaust to all happen in a single revolution of the rotor, making it more efficient than a comparable four-stroke piston engine, which delivers one power pulse every two revolutions. Compared to a conventional engine of equivalent output, the rotary is smaller, lighter, and, because it has no reciprocating parts, quieter and smoother as well.

Mazda didn't invent the idea, but they were the ones with the stubbornness and engineering talent to actually make it work. Early prototypes suffered from "devil's fingernails”, or chatter marks scratched into the housing by the tip seals vibrating at their natural frequency, as well as heavy oil consumption. Mazda's engineers solved the seal problem by redesigning the apex seals' resonance frequency, and addressed oil burning by adding a tiny amount of lubricant to the fuel mixture. It worked at the time. The resulting 982cc 10A engine in the Cosmo Sport produced 110 horsepower at 7,000 rpm and pushed the car to a top speed of 124 mph, genuinely impressive figures for 1967 and for an engine that displaced less than a liter.

A Brilliant Engine With One Very Expensive Flaw

Here's where the story turns complicated. The same characteristics that made the rotary so simple also made it prone to poor sealing at the three rotor tips. And poor sealing meant one thing: unburned fuel slipping past into the exhaust. To address overheating at the rotor tips, Mazda added a tiny drop of oil to the fuel mixture for cooling, which sorted the thermal