It doesn't come easy's Journal: Mazda's New Smart Idling Stop System

Now this is really thinking outside the box...Mazda is displaying a new form of an idle-stop system for direct-injection spark-ignition engines that uses combustion and the reverse operation of the engine as a restart trigger rather than an electric motor. To summarize: The Smart Idling Stop System shuts off the engine when you come to a stop. When you want to go again, the system injects fuel into the cylinder in the compression phase but not yet at the top of the compression cycle (in a four cylinder 4 stroke engine, one cylinder is always in the compression phase). Then the fuel is ignited to force the compressing piston back down in the opposite direction. This causes compression in a different cylinder which then has fuel injected and ignited, which in turn forces the engine to turn back in the normal direction and provides enough power to kick start the engine back to life. In order for everything to work, the Smart Idling Stop System forces the engine to stop in a position that is optimal for the next restart attempt. Mazda claims that the Smart Idling Stop System is more energy-efficient than an electric motor restart, and also restarts the engine more quickly and quietly than a conventional idle-stop system.