Skyactiv is out now, but only the beginning. From here, it gets freaky. As in: no coolant.
Engine geeks will know that Mazda is foregoing battery anything by betting on new internal combustion engine tech. The current Skyactiv engines already do that by having very high compression rates for petrol engines, and very low ones for diesel.
For the diesel engines, reducing compression to 14:1 means much lower burn temperatures, which means fewer NOX and particulates, which means that the Mazda diesels can do without complicated additive injection systems and still meet the latest norms. Not that they're trying in the US, but hey. Also: 20% more efficient than pre-Skyactiv-D oil burners.
For the petrol engines, raising compression to 14:1 means a more complete, efficient burn, with lots of trickery like funky pistons to prevent the engine from 'knocking'- i.e. self igniting at the wrong point. Result: 15% more efficient than previous Mazda engines under low or medium load (except in the US where the compression ratio is 13:1, because crap petrol)
And according to Autocar and Heise, that's where they're going for the second generation of Skyactiv: they'll let petrol engines self-ignite – just like a diesel – in most situations; i.e. less than half load. When really giving the engine some welly, though, spark plugs are still called for. Moving from self-ignition to sparks seamlessly and smoothly is what Mazda's working on now. Result: 30% efficiency improvement over current Skyactiv engines.
Mercedes are also working on such a freak of nature, and they refer to it as diesotto - 'diestrol', or 'gasel', if you like.
But the Mazda guys are looking beyond that to the generation beyond: homogenous ignition. Rather than have the dino juice ignite from a spark (petrol) or an injector's jet (diesel), it all self-ignites at once. Advantage is that there's optimal thermal efficiency, to the point where they're thinking they'll need to insulate cylinders to make the whole ignition process as efficient as possible.
Result? 30% greater efficiency over second generation Skyactiv, meaning cars that will be cleaner 'well-to-wheel' than full electric vehicles. Or so says Mazda.
Will this trickery save 'proper' engines in the long term? Who knows, but it'll be fun to watch.