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Rotary engine an alternative to typical piston powerplant

Josh Blair

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Josh Blair

Sometimes it’s not easy being different. Most people disregard and disrespect that which they don’t understand.

In the world of automobile engines, the rotary engine is that misfit.

Mechanics

The rotary engine operates without pistons, valves, cams, a timing belt or other parts found in a typical engine. It accomplishes this feat using two triangle-like rotors mounted on an eccentric shaft in two oval-shaped housings. The two housings are sandwiched together along with three side housings and a front cover.

Each of the three faces of the rotors perform the intake, compression, combustion and exhaust cycles in one full rotation of the rotor. A piston must rotate twice in order to complete these actions.

There are seals at the apex of each rotor that maintain compression within the housing. Seals on the side of each rotor also help hold compression.

The intake and exhaust ports are located in the rotor housing. The ports lack valves because chambers on the rotor faces control the intake and exhaust cycles.

The intake port is mated straight to the throttle body and the exhaust port is mated straight to the exhaust system.

History

The rotary engine is sometimes called the Wankel rotary engine after Dr. Felix Wankel, the German mathematician who developed the rotary engine in the 1950’s.

The only American market cars using the rotary engine are the Mazda “R” series of cars starting with the R-100 and ending with the recently released RX-8. The most popular rotary engine equipped car is the RX-7, which went through three generations in America from 1979 to 1995.

Major automobile manufacturers such as General Motors and Mercedes attempted to produce rotary engine vehicles, but found the task too challenging.

The AMC Pacer and the Chevrolet Vega were both scheduled to be powered by a rotary engine, but the engine was scrapped near the end of production.

Advantages

Two aspects that make the rotary engine superior to a piston engine are its small size and light weight. Because of the small size, a rotary engine can be placed lower to the ground and farther back in an engine bay. This improves a car’s weight distribution. Less weight improves a car’s handling, gas mileage and power.

The rotary engine also contains only three moving parts, as opposed to a piston engine in which the simplest four-cylinder engine has at least 40 moving parts. Howstuffworks.com states that the “minimization of moving parts can translate into better reliability from a rotary engine.” The Web site also states that rotary engine parts move slower than piston engine parts, adding to their reliability. With fewer moving parts there is also less engine vibration.

Fewer parts also make rotary engines easier to rebuild.

Disadvantages

One problem people associate with the rotary engine is that it blows relatively easy.

While there are many blown rotary engines, a larger factor is how the owner maintains the engine.

As long as the oil is changed regularly, the engine is kept cool and the car is driven frequently, a rotary engine can last more than 200,000 miles.

Another major problem with rotary engines is carbon deposits. If carbon, released from the ignited gasoline, starts building up in the engine, then the engine’s apex seals can crack over time. This damage causes a loss in compression.

To prevent carbon build-up, rotary engines need to be driven regularly and revved high on a regular basis.

Rotary engines also consume more oil than piston engines because oil is injected into the combustion chamber to lube the apex seals.

There is also a shortage of knowledgeable rotary mechanics. When rotaries became popular in the late 70’s and early 80’s, few mechanics found it necessary to learn about them. It’s difficult to find mechanics who understand a rotary engine enough to know how to properly repair or rebuild one.

The rotary engine may only be known by some and understood by few; but it seems as though it’s here to stay.

Hopefully, if more people understand and appreciate the rotary engine, it will come equipped in more than one car and be produced by more than one manufacturer.

The rotary engine may be different, but that’s not important.

Because it rolls like that.

E-mail questions to Josh at blairjo@nku.edu

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The Independent Student Newspaper of Northern Kentucky University.
Rotary engine an alternative to typical piston powerplant