When Mazda finally shut down production of the Renesis rotary-powered RX-8 in June 2012, the cybergarage was abuzz with stories of a next-generation rotary engine, somewhere behind locked doors at the Mazda skunk works.
At the time we put the rumours down to wishful thinking on the part of rotary enthusiasts; much as we love the simplicity, compactness and bang-for-your-buck power output of the Wankel engine, like the two-stroke motorcycle engine, it's just too thirsty, too dirty, too lacking in torque and too maintenance-intensive for the eco-obsessed world we live in.
Well, we were wrong; at the weekend's Pebble Beach Concours d'Elegance in Monterey, California, a Mazda USA staffer apparently told Autoblog that the 16X engine was very much alive and under development to address just those issues.
More than that, he said, the new engine would power an all-new Mazda, due for release in 2015 as a 2016 model. Whether that means a sleeker, prettier four-seater RX-9 with reverse-opening suicide doors, or a cute little two-seater barchetta (think Miata on steroids!) is still classified; it may not even be final yet.
But how to sanitise the rotary? Like the aforementioned two-stroke, a rotary gets a critical proportion of its lubrication by burning oil as part of the combustion process; apex seals may improve (in fact, they will have to) but it may only be possible to clean up the exhaust emissions downstream, using some variation of Mercedes-Benz's Bluetec fluid.
Secondly, we all know that the way to increase torque and reduce fuel consumption in a reciprocating engine is to lengthen the stroke - but the combustion chamber shape and rotor geometry of a Wankel engine are finite - you can't even define the stroke, let alone increase it.
Or can't you? According to what the Mazda guy told Autoblog, stroke is defined as “the path of travel within the combustion space”. Note that he didn't say combustion chamber - a rotary doesn't have one - but it does offer the possibility of increasing the distance between the inlet and exhaust ports to create the desired longer path.
The nature of the rotary cycle makes that very difficult, but it's not impossible. The Renesis engine, in fact, has radically different porting to the original Wankel layout, partly for the same reasons.
So, rotary lovers, it would seem that there is reason for cautious optimism; there has always been strong support for the rotary among Mazda's engineering staff, albeit in the teeth of opposition from the bean-counters - the fact that the 16X project still exists, says something important about Toyo Kogyo's corporate culture.
As soon as we hear any more details of the next-generation Maxda rotary, so will you.