https://www.motor1.com/news/447897/m...n=RSS-all-news
This is pretty interesting. The old Renesis had a best BSFC around 270g/kWh (~31% thermal efficiency), which really isn't worth the space savings of a piston engine.
I've read a bunch of Paul Moller's research papers and it seems that by far the biggest problem with a rotary is unburned fuel. Charge cooling the rotor (aka a warm air intake) and increased rotor temperature dramatically reduce unburned fuel and bring the efficiency more in line with piston engines, but decrease torque (which isn't a problem on a range extender).
Additionally, the oil cooled rotor on the Renesis produced a lot of windage, so roller bearings on the crankshaft can help high rpm efficiency considerably.
I'm guessing this range extender concept probably uses either thermal barrier coatings, a charge cooled rotor, or both, to bring the internal surface temperatures up, and hopefully uses silicon nitride seals to avoid frequent apex seal service. I wonder if customers would fret at having to top up the engine with lubricating oil though.
Additionally, the 16X concept supposedly was all aluminum, having solved the cooling issues, so such an engine would be VERY lightweight (probably <200lbs for a 1.3L 2-rotor configuration, whereas a piston engine producing similar power and torque weighs around 300lbs).
If they can get the thermal efficiency to 36%, that would be pretty impressive. In a smaller car, saving 100+lbs of mass at the engine probably could make up a good chunk of the fuel efficiency gap to a more efficient piston engine. It would make a great motorcycle engine as well.