Rotary Love
How many of you readers know what a Wankel rotary engine is? Don't be shy now, raise those hands up so I can count you. Only a couple? That's fine, that's why I am writing this article: Prepare for a quick education!
Here is my 1991 Mazda RX-7 Turbo II:
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| I get honked at a lot... |
Take a guess as to how many cylinders this baby has. Many folks assume this little car is rocking a four cylinder engine, simply due to its size. While a 2.5 liter four banger may fit nicely in here should I want to swap engines, the truth is my car had zero cylinders and a much smaller displacement than nearly every four cylinder engine on the road today.
How can this be? Is it an electric car? Surely it is too old to have a battery that would power it for any reasonable distance. Zero cylinders? It must be magic!
No, it isn't magic, its a 1.3 liter (1300 cc's) turbocharged rotary engine. It has two triangle shaped rotors housed in a pair of trochoidal rotor housings. These two triangles whip around a specialized elliptical shaft which then transfers the power directly to the main drive shaft. Got it? If not, here is a perfect, simple animation to help you understand how a rotary engine functions:
With the stock setup and a boost level of around 6psi, my car puts down 200 horsepower to the rear wheels. Rotary engines have the benefit of being able to rev to astronomical levels. And the higher the revs go the more power the engine produces. My particular car has a redline at 7,000 RPMs. It even has an alarm buzzer that goes off once your tachometer swings past 7k, letting you know that, while this is fun and all, shifting may be a good idea right about now.
These motors have been around for quite awhile, but Mazda has always been the company to put them into widespread production. Starting with the Mazda Cosmo Sport in the 1960s, and most recently with the RX-8, rotaries have revved their way into the hearts of anyone whose had the pleasure of driving one.
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| A beautiful green Mazda Cosmo Sport |
Another benefit of rotary engines is that you can mod and tune them to your heart's desire. They are able to handle a remarkable amount of power for their size. Some 3rd generation RX-7s are able to put down 800+ horsepower by turning up the boost on their turbos (or getting larger ones), and then tuning the fuel system to handle a different gas to air mixture ratio.
Do rotaries have a downside? Alas, yes they do. A stock rotary engine will usually make it to 120,000 miles and then blow up. The corners of the triangle shaped rotor have seals (called 'apex' seals) that can only handle so many revolutions inside the rotor housing before failing. My RX-7 made it to 118,000 miles and then, like so many other rotaries driven that far, my apex seals blew and I had to have the engine rebuilt. This is a pricey proposition for most folks, even though the engine has about one tenth of the parts that a traditional piston engine contains. Many mechanics won't touch rotaries because the rebuilding process is so much different than what they are used to. Many people simply send the car to the junkyard to rot or replace the rotary engines with a V8 or other piston engine. While wanting a piston engine with generally better reliability in the long run is understandable, there is still nothing quite like a Wankel.
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| 3rd Generation RX-7: One of the most beautiful cars in the world. |
So I challenge my rotary loving brothers and sisters to keep the dream alive! Don't sully your car's reputation by replacing a blown Wankel engine with a piston engine. That way you can chuckle to yourself at Jiffy Lube when the oil change man asks you how many cylinders your engine has, and reply: "Oh my car has no cylinders. My car is powered by exploding triangles."
Their faces will be priceless.
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