What Is a Wankel Engine?

When you think of an internal combustion engine, you probably think of an engine that uses reciprocating pistons. It's true that the vast majority of internal combustion engines use this kind of design, but there are a few engines out there that are a little different.

One of the most famous alternative internal combustion engine designs is the rotary engine, and specifically the Wankel variant of the rotary engine. While Wankel engines have only been used in a few cars over the years, these engines have nonetheless become fairly iconic.

In today's article, we'll be going over everything you wanted to know about Wankel engines, including who invented them, why they were invented, and why they never quite managed to catch on.

Wankel Engines Explained

As we've mentioned, a Wankel engine is a kind of rotary engine. If you don't know what a rotary engine is, however, this won't mean anything to you, so let us explain.

Unlike a normal internal combustion engine where power is generated by the reciprocating motion of the pistons, power in a rotary engine is generated by the rotation of a rotor. A rotary engine consists of a cylindrical barrel containing one or more rotors that are mounted on a central shaft.

When combustion occurs inside the engine, it causes the rotors to spin, which in turn creates power via a central shaft that the rotors are attached to. The rotors in a rotary engine can get up to some pretty impressive speeds; it's common for rotary engines to operate at speeds between 7,000-9,000 rpm.

What sets Wankel engines apart from other rotary engine designs is the shape of the rotor. Wankel engines use a three-sided rotor with slightly curved sides, similar in shape to a Reuleaux triangle. It's the shape of the rotor that is one of the most distinctive aspects of a Wankel engine's design.

Who Invented the Wankel Engine, and Why?

The Wankel engine was originally conceived in the 1920s by Felix Wankel, a German engineer. He received the patent for his design in 1929, although his design wasn't actually put into production until over two decades later; unfortunately, Wankel spent much of the time between 1920 and 1945 supporting the Nazi party.

The reason for the creation of this design was simple; piston engines at the time typically caused a lot of vibration, and Wankel's design aimed to eliminate much of this vibration and hopefully result in a smoother, more comfortable ride. His design also had a few other advantages over piston engines, but we'll get to that later.

During World War II, Wankel worked with the German navy and air force designing rotary valves and seals for torpedoes. When the war ended, however, the French jailed him for several months; in addition, his work was confiscated and he was initially prohibited from working anymore.

In 1951, the NSU Motorenwerke company began developing a rotary engine for use in their cars and asked Wankel if he'd be willing to help him out. He accepted, and by 1957, the first working prototype of his engine had been made.

While we know Felix Wankel as the inventor of the Wankel engine, the Wankel engines that appeared in cars later weren't actually his design. After Wankel completed his prototype, another engineer at NSU named Hanns Dieter Paschke reworked his design to make it easier to mass-produce.

The first production car to debut with Wankel's new engine was the NSU Spider, a small convertible sports car. The engine in this car was a 498 cc single-rotor unit making between 50-54 horsepower, which gave the Spider a 0-60 time of around 15 seconds. While this wasn't that fast, it also wasn't that much slower than many other cars being sold around the same time.

What Are the Advantages and Disadvantages of Wankel Engines?

Wankel engines have several advantages over reciprocating piston engines, but they also have several disadvantages that have kept them from being used more widely. Let's take a look at some of the advantages and disadvantages Wankel engines have compared to more conventional engines.

Advantages

One of the main advantages of the Wankel engine, and the reason Felix Wankel invented the engine to begin with, is the fact that Wankel engines run very smoothly. This is mainly due to the fact that Wankel engines don't have any reciprocating parts, which generally cause a lot of vibration.

In fact, Wankel engines have far fewer moving parts in general than a reciprocating piston engine. As such, Wankel engines generally require less maintenance than piston engines.

Because these engines have fewer parts, Wankel engines are also a lot lighter and more compact than piston engines. Wankel engines are also a lot better at producing more power from a smaller engine displacement than comparable piston engines.

Disadvantages

Unfortunately, Wankel engines also have their share of disadvantages, which have kept them from gaining more popularity. Probably the biggest disadvantage is that while Wankel engines are easy to maintain, they're not all that reliable. In short, Wankel engines can be fixed easily, but they require fixing more often.

One of the biggest issues in this regard is the fact that the engine seals frequently need to be replaced. Because there are often significant temperature fluctuations inside the engine, this tends to wreak havoc on the seals.

While Wankel engines can produce more power than piston engines of an equal displacement, they're also a lot less fuel-efficient than piston engines. This is due to the fact that rotary engines don't combust fuel as thoroughly as piston engines.

Because of this, Wankel engines also tend to produce more emissions than piston engines. They also produce more emissions thanks to the fact oil is injected into the combustion chamber to provide lubrication, so Wankel engines are usually burning oil as well as fuel. It's pretty common to see blueish oil smoke coming from the exhaust of a car with a Wankel engine.

Why Are Wankel Engines Not More Widespread?

While several cars have used a Wankel engine over the years (with Mazda being the most prominent manufacturer of Wankel engined cars to date), Wankel engines have failed to gain any kind of real popularity in the automotive world. So what exactly is the reason for this?

Well, as it turns out, the reasons why Wankel engines aren't more common are directly related to the disadvantages we talked about in the previous section. These days, the biggest reason why we don't see more Wankel engines being used is the lack of fuel efficiency and increased emissions.

You're no doubt aware that we as a society are paying more attention than ever to the emissions our cars produce and are moving closer and closer towards adopting alternative fuels and power types into the mainstream. As you can imagine, this doesn't leave much room for dirty engines like Wankel engines.

It's been quite a while since we had a new car that came with a Wankel engine; the last one to come out was the Mazda RX-8, which debuted in 2002 and was in production until 2012. But does this mean the Wankel is dead forever?

As it turns out, not quite. Mazda has recently announced that they'll be bringing back the Wankel, although not in the way you might expect. Instead of appearing in a sports car, Mazda's new Wankel engine will appear in the upcoming MX-30 hybrid. In this car, the rotary engine will function solely as a generator for the car's batteries.