NoPistons -Mazda Rx7 & Rx8 Rotary Forum

This is a short paper I wrote for a technical writing class, in which the assignment was to take a technical article and "translate" it into more simple terms, whils also adding a bit or background about the previous state of knowledge on the subject, and some possible future implications. Please leave feedback, as this is a rough draft.

“Hydrogen Technology Creates a Cleaner, More Efficient Rotary Engine”

For the last hundred years or so, the dominating force powering automobiles has been the internal combustion Otto-cycle engine. This engine is what is in your typical day-to-day car; a four-stroke engine, comprised normally of four, six, or eight cylinders. Containing pistons, valves, camshafts and crankshafts, these engines are in almost every automobile ever produced. The only other internal combustion engine design to be used in a production automobile is the Wankel Rotary Combustion Engine (WRCE). With gas/electric hybrid technology taking off, Mazda is stepping up to the plate and delivering wonderful new innovations like the hydrogen rotary engine.

Rotary Background

In the 1930’s, a German scientist by the name of Felix Wankel was working on a revolutionary design for an internal combustion engine, which later developed into what we know today as the Rotary Engine. Wankel’s design is unique in that it utilizes none of the components found in a typical internal combustion engine. Instead of the typical up-and-down motion of the pistons, with valves opening and closing to allow air, fuel and exhaust through, picture this: A triangle spinning inside an oval that has had its sides pinched in. Picture that and you can see how truly unique the Rotary Engine is.

Advantages and Disadvantages

While a piston engine only produces power through 180 degrees of rotation, or 50% of the time, a rotary produces power through 270 degrees, or 75% of the time. This allows a rotary engine to produce roughly twice as much power as a piston engine of equal displacement. Additionally, rotaries have extremely smooth power delivery.

This being the case, why are piston engines still the standard, while rotaries are stuck in the background, only to be used by a small group of die-hard sports car enthusiasts? The main reasons for this are that firstly, rotaries get unusually bad gas mileage, and secondly, that exhaust emissions are high with rotaries. Because of their design, rotaries of the past were doomed to guzzle gas and spit smoke. The reason for this is that rotaries have “ports” which are always open. This allows unburned fuel to exit the motor, instead of being recycled, and then it gets burned in the exhaust, releasing excess hydrocarbon emissions.

The Rotary Engine Returns

Since 1991, Mazda engineers had been toying with and refining the idea of a hydrogen rotary, but none of the previous incarnations were feasible for production. In 2003, with the re-introduction of the rotary engine (Now dubbed RENESIS) to the American market, Mazda had finally found the appropriate time to introduce the hydrogen rotary. The vehicle in which Mazda had placed this new motor was the new (rotary-powered) sports car, the RX-8.

Hydrogen + Rotaries=Efficient, Powerful, and Eco-Friendly

The RENESIS engine utilizes new technology, including exhaust scavenging and supplementary spark plugs, to reduce both hydrocarbon emissions and increase fuel mileage. This, Mazda saw, was the ideal platform on which to build the hydrogen technology.

There are several innovations that make the hydrogen rotary in the RX-8 stand out from the crowd:

1)-The gasoline motor (producing 220 horsepower) is electrically-assisted, much like conventional hybrid gas/electric engines. At stoplights, the gasoline motor is turned off to conserve fuel, and the electric motor assists in acceleration from a stop while also re-starting the gas motor.

2)-The Hydrogen system used is brand-new, with more powerful hydrogen injectors, which allow the hydrogen to be burned more completely and efficiently. An in-car button allows the driver to switch over to the hydrogen fuel, which allows the engine to produce 110 horsepower.

3)-Self-regenerating electrical system uses the car’s brakes to recharge the batteries. The 144-volt system never needs plugging in, because the brakes’ excess energy is used to recharge it.

These factors all add up to a powerful, clean, and efficient powerplant. Placed in a highly aerodynamic vehicle such as the RX-8, this motor is one of the most efficient on the planet.

Implications and The Future of the Hydrogen Rotary

Although this technology is ground-breaking and innovative, it is still in its infancy. Hydrogen, along with other alternative-fuel technologies such as biodiesel are using these breakthroughs as stepping-stones.

More importantly for Mazda, the rotary engine’s ability to use hydrogen more efficiently than piston engines could create a niche for the rotary engine to fill. Where the rotary engine of today is seen as an oddity, only respected by a core group of enthusiasts, the new hydrogen RENESIS could change the rotary from a gas-guzzling pollution monster into an eco-friendly and efficient power source.