When buying a brand-new car, the question of the engine’s construction hardly comes up, nor is it listed on the manufacturer’s website. While there are different engine sizes, configurations, and even forced induction, they all use cylinders and pistons. However, in the 1950s, a man named Felix Wankel developed an entirely different kind of engine. Widely known as the rotary engine, it was smaller, lighter, and often more powerful than piston-powered competitors.
How does a rotary engine work?
To understand what makes the rotary engine unique, we first need to know how a traditional piston engine works. Intake valves allow air to flow into the cylinders. As the pistons move downwards, they suck air into the combustion chamber. At this point, a fuel injector adds fuel to the mixture. As the piston moves back up, it begins to compress the air in the chamber. Once at the top, a spark plug ignites the mixture, pushing the piston back down. This movement repeatedly happening at a lightning-fast pace is what allows the engine to develop its power.
A rotary engine, on the other hand, goes about the same process in a very different way. Instead of having a piston that moves vertically, a rotary engine utilizes a rotor that spins on an axis. Firstly, air and fuel are sucked into the combustion chamber by the vacuum created by the spinning rotor. As the rotor spins, it compresses the air, at which point two spark plugs ignite the mixture. The exhaust gases are then allowed out of the combustion chamber by the rotor, only to suck in more air and fuel as it completes another rotation. This spinning motion is what allows the engine to make its power.
Who developed it?
While Felix Wankel conceived the original design for the rotary engine, Mazda popularized it. According to Mazda, in 1960, various manufacturers signed licensing agreements to build the engine; however, only Mazda ever managed to make it commercially viable. Mazda’s first rotary-powered vehicle was the Cosmo 110S, which like the name suggests, produced 110 hp from its two-rotor configuration.
From then on, the rotary was a hit, eventually spawning the RX line of sports cars we know and love today. One of the standout models to utilize a rotary engine was the third-generation RX-7, which was in production from 1992 until 2002. A 1.3-liter twin-turbo 13b twin-rotor engine powered the RX-7. The complex powertrain developed 236 hp.
Why is it so uncommon?
By design, the rotary engine is ideally meant to live in a world of motorsport. Part of the reason we don’t see rotary engines in mass-produced vehicles, namely, has to do with the maintenance costs. While there are fewer moving parts in a rotary engine, the throttle directly affects how much oil is in the chamber, lubricating the rotor and all of the seals.
When the throttle is not in use, like in stop and traffic situations, the seals can dry up and fail. Also, the rotor itself may not be adequately lubricated, damaging the combustion chamber, resulting in a loss of compression. These requirements mean that to upkeep a rotary, the maintenance has to be meticulously done. As a result, the commercial viability of the rotary began to fade, eventually being phased out of production by Mazda in 2012.