Mazda SkyActiv-R patent application_lead
True fans of the rotary engine are praying that Mazdaâs March 24 U.S. patent application means that the resurrection of this free-spirited alternative to pistons is not far off. While itâs been nearly four years since the final rotary engine was built for an RX-8, hope springs eternal that Mazdaâs sacred powerplant will hum again.
Since the Renesis II 16X engine program was introduced at the 2007 Tokyo Motor Show, Mazda has insisted that its engineering team had been working feverishly to bring a new rotary up to modern power, fuel-consumption, exhaust-emissions, and reliability standards. Last year Mazda stole the Tokyo show with its RX-Vision two-seat coupe concept, which presented a stunning wrapper but no engine updates beyond a fresh rotary-engine name: SkyActiv-R.
What we know about the SkyActiv-R is that it features aÂ 23-percent-larger displacement than the 232-hp 13B engine which powered the RX-8.
The larger size and internal geometry changes are aimed at solving a key rotary issueâthe impression that no oneâs home at low rpm. To save weight, the SkyActiv-R usesÂ aluminum end plates where the 13B used iron pieces instead. Injecting fuel closer to the combustion chamber improves fuel efficiency.
The Mazda RX-Vision concept won the Tokyo auto show last fall.
Even though turbocharging is contrary to core SkyActiv tenets, this new rotary will definitely be turbocharged to produce the 400-plus horsepower it will need to compete against Corvettes, Jaguars, and Porsches. The most interesting insight revealed by U.S. patent 2016/0084158 is Mazdaâs intent to twirl its rotary engine 180 degrees about its longitudinal axis. This is feasible because, just like in piston engines, the internal components are happy converting air and fuel to torque and power no matter what their orientation.
The main reason for this rotation is packaging. Looking at the front of this engine (the view at the top of this post), moving the exhaust ports and the turbo from the bottom-left corner to the top-right clears space for the front chassis cross member and suspension components while allowing the engine to be mounted lower in the car.
Mazda SkyActiv-R patent application
This drawing from Mazda’s patent application shows the engine from the left side; note the exhaust systemÂ now sproutsÂ from the top of the engine. The image at the top shows the SkyActiv-R from the front.
The top location shortens the length of the exhaust system so minimal heat is squandered before flow reaches the catalyst. Thereâs also more space available at the higher altitude for a larger turbocharger; donât be surprised to see a bump in the hood of a production version of the RX-Vision. This reorientationÂ also improves life at the intake side. Moving the intake ports from the top-left to a bottom-right location enables longer runners. These provide a ram-tuning benefit, augmenting torque at low rpm before turbo boost arrives.
Unfortunately, Mazdaâs patent application offers no hint as to how engineers will remedy the rotaryâs poor thermal efficiency. This is caused by the combustion chamberâs high surface-to-volume ratio, which is greater than any contemporary piston engine. Excessive surface area drains heat energy into the cooling and lubrication systems, diminishing whatâs available for producing power.
Nevertheless, the rotary rumor mill reports that the RX-Vision is moving from the static concept to the working-prototype stage with production intent. Our agents are standing guard at the patent office to see whatâs next for Mazdaâs rotary.