Mazda rotary engineEnlarge Photo
Mazda is a relative minnow in the auto industry sea, but for such an independent company it punches above its weight in engineering terms.
It's still one of few companies to offer a simple two-seater sports car in a world of more profitable crossovers and hatchbacks. It's developed an entirely new and advance line of engines--under the Skyactiv banner--without any external input. And Mazda still persists with the Wankel rotary engine.
Mazda now fits a rotary engine to the Mazda 2 subcompact, but not in the form you might expect.
It's not a screaming, turbocharged rotary hot hatchback--fun as that sounds. Instead, Mazda is using the rotary engine as a range-extender in an electric vehicle--supplying power to keep its batteries topped up and effectively doubling the car's range.
The Mazda 2 you're familiar with typically uses a 1.5-liter gasoline four-cylinder, or a 1.3-liter unit in some markets. Here, you get a 100-horsepower electric motor up front, and a 330cc rotary sitting under the rear cargo deck.
It only produces 29 horsepower but that's not such a problem, as its sole purpose is to whir away when required to top up the battery pack. This boosts range to around 300 miles, despite using a tiny 2.3 gallon fuel tank--a little like BMW's i3 REx.
That figure is on the Japanese testing cycle of course--heavily biased towards city driving and therefore unrepresentative of real-world range outside of Japan.
Smooth, quiet, efficient
The benefits of the rotary range-extender are clear though. Like any range-extended car--the Chevrolet Volt, for example--you get to make use of all the best characteristics of electric cars: smoothness, silence, low-down power and of course, cleanliness.
Yet when the range-extending engine kicks in, it's smoother and quieter than a reciprocating combustion engine. It's also more compact, letting it fit below the trunk in a car as small as the Mazda 2, and because it's been optimized to run at constant revs, the usual fuel and oil consumption issues of rotary units don't apply here.
2014 Mazda 2Enlarge Photo
According to both Auto Express and Drive, who've driven Mazda's prototype, the unit is virtually inaudible unless you're sitting closer to it, in the back seat. That echoes our own findings in Audi's similar concept--the rotary range-extended Audi A1 e-tron we drove earlier this year.
Prototype niggles aside, that car proved as easy to drive as any electric vehicle, and the running rotary produced little more than a distant hum--with virtually no vibration or noise.
Mazda also promises low fuel consumption for the unit, and low emissions--around 13 grams per kilometer of CO2, similar to that of the BMW i3 REx.
Economies of scale
This is where Mazda's independence would normally curtail such a project.
Nobody else really develops rotary engines any more. And when you're a small car company with nobody to share the development costs, such a project can struggle to turn a profit.
But Mazda thinks it's found a way. So efficient and small is the unit, Mazda says it can be used in non-automotive applications--such as emergency generators and other static uses.
And with the costs covered and engineering improved on projects like this, the company can even supply car enthusiasts with the rotary sports car they've been asking for ever since the RX-8 died. It's win-win.
Would you like to see the rotary engine return as an efficient range-extender? Leave your thoughts in the comments section below.