Remember, a rotary engine doesn’t have any valves, so this latter step is a must. Also described is the concept of "firing a spark plug after the fuel has been cut to eliminate any leftover fuel emissions." Interesting. This new tech would hopefully improve fuel economy and emissions. Now, here’s where things get even more interesting: that rotary engine start-stop patent is also combined with the range-extender powertrain patent. Think about it. By combining the technologies together, Mazda can, theoretically, still use a rotary engine, only one that’s combined with a start-stop system, an electric motor, and lithium-ion battery.