What is a Wankel Rotary Engine? A Brief Description

The task of giving a brief explanation of what a Wankel Rotary engine is, can be difficult however I will try to achieve this as best as I can.

 

The Wankel Rotary engine is an internal combustion engine that was developed and patented in the 1920’s by Felix Wankel and versions have been used in aircraft, helicopters, snowmobiles, motorcycles, autos and many other applications. The Wankel Rotary engine we are most familiar with (and is most commonly known for its use) is in the Mazda RX Series of sport cars, which was developed by Hanns Dieter Paschke. The last production of the Mazda RX series was the RX-8 in 2012. This pull from production was due primarily to its poor fuel economy and emissions.

 

To best describe this engineering marvel, the Wankel Rotary engine accomplishes the same task as the more common piston engine however using a different process. The main difference between a rotary engine and a piston engine is that the rotary engine doesn’t need to convert the up and down reciprocating motion of the piston into a rotational force. The biggest advantage of a rotary engine is how much power it can produce for its size. An example of this would be the version used in the 2012 Mazda RX-8, it was a 1.3 liter however it produced 232 horsepower. Pretty amazing!! Not only is the displacement small, the physical engine size is much smaller and lighter than a typical 4-cylinder engine.

Photo credit: J. Lyon [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons
 

There are two main moving components within a rotary engine which consists of the rotor, a rounded triangular shaped component creating three separate chambers or spaces within the rotor housing, and an eccentric shaft which is the equivalent of a crankshaft in a piston engine. The rotor has an apex seal placed on each of the three tips or apex and is the only part of the rotor coming into direct contact with the rotor housing. The Rotor housing is a barrel shaped housing allowing the rotor to spin around within the housing while fuel and air are pumped into the spaces between the rotors’ sides and interior walls of the barrel where they ignite. During the combustion process, the rotors are turned, generating the power. All of this is achieved with fewer moving parts resulting in a smaller and lighter engine of equal displacement. In comparison, the piston engine requires, pistons, valves, a crankshaft, connecting rods along with a camshaft, valve lifters, valve springs and other mating components.

 

Most engine enthusiasts love the Wankel rotary engine in part because it’s different as it hardly resembles a conventional piston engine. Why?, Power is delivered linearly all the way up to 7,000-8,000 RPM, of course depending on engine set up and tuning, and the flat power band sets it apart from piston engines that too often produces the power at high RPM while feeling pretty weak at low RPM

 

It has been rumored there will be a comeback of the Wankel Rotary engine used as a range extending generator in a plug-in Hybrid vehicle in 2020. It is said to be paired with an electric motor to provide power when the battery runs down. The fuel economy and emission concerns are being addressed for use in modern day applications and in specific markets we may see a non-hybrid version available. Until then, we will have to wait and see what the next chapter is in the history of the Wankel Rotary Engine!

 

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