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Mazda has filed patents for a hybrid powertrain that includes the return of the legendary Wankel rotary engine, complete with capacitors and a lithium-ion battery. This system could find a place in a future RX-9…
The Mazda MX-30, the first 100% electric vehicle presented at the Tokyo Motor Show for 2025.
When Mazda unveiled its first electric vehicle, the SUV MX-30, the first surprise came from the battery capacity of 35.5 kWh – a range of 210 kilometers. A bit tight against Peugeot e-2008, Hyundai Kona and other Kia e-Niro.
For the Japanese manufacturer, there is no need to overbid on the battery side, since drivers travel around 50 km in a day. However, Mazda does not forget those who would like to have a "reserve". Thus, the MX-30 is also available with a range extender or “Range extender” or Rex, in English.
This technology that made the heyday of the first BMW i3s came in the form of a 34hp twin-cylinder engine (from the motorcycle branch of BMW), accompanied by a tiny 9l tank. Its function consisted in serving as a generator for the electric battery when the autonomy tended to run out of fuel. Thanks to him, we had an additional range of 150 km.
But the contribution of large batteries, new WLTP standards and a densifying charging network, the death warrant for the Rex at BMW was signed.
Recommended item: BMW i3, an electric car that turns heads
As for Mazda, its range extender uses the legendary Wankel rotary engine which fitted the famous RX-7 and RX-8. Nicknamed "Dorito" by its triangular shape, which is reminiscent of the famous chips, the Wankel is also the only pistonless engine to have won the 24 Hours of the Mans in 1991 with the Mazda 787B.
The “Range extender” The SUV MX-30 is made up of the electric motor which drives the front wheels while the Wankel rotary motor takes care of recharging the battery when it is on the verge of starvation. The whole system takes place in the engine compartment, at the front.
Wankel sauce hybridization
This return of the Wankel rotary motor is not trivial. This could also be the centerpiece of future hybrid powertrains at Mazda. This is at least what suggests the patent filings by Mazda, discovered by the Japanese television channel T's Media.
As shown in this technical diagram, the front wheel hubs (10 in number) each have an electric motor. We also notice the capacitor (CAP). At the rear, the 3.5 kWh 48 V battery. © j-platpat / Mazda
According to the Motor Trend site which analyzed the documents, this is a major update of said patents which concern two types of thermal combustion vehicles: traction and propulsion. They also have two electric motors located in the wheel hubs of the front axle and a third, located at the rear. The whole thing is completed by a capacitor, three inverters and a small 48 V lithium-ion battery with a capacity of 3.5 kWh.
Front part with the configuration of the V-shaped motor with the capacitor (7a) in the middle. © j-platpat / Mazda
Profile of a front wheel with its electric motor. © j-platpat / Mazda
But the most interesting is in the latest patent update which shows a "V" motor and a Wankel rotary motor. Motor Trend explains that the latter, placed at the front, indirectly drives the rear wheels. Indeed, instead of a traditional flywheel, the drawing reveals an electric motor (synchronous with permanent magnets) of 25 kW accompanied by an inverter and a current transmission shaft up to the gearbox-bridge . Said electric motor can drive the rear wheels alone or with the aid of the internal combustion engine.
Another peculiarity of this patent: the position of the gearbox which is found at the rear as on the Nissan GTR or on the Corvette. In general, this choice allows a better distribution of the masses. Here, it is also saving space in the passenger compartment with the absence of an overhanging transmission tunnel.
Capacitors as a battery
At the front, the internal combustion engine accommodates two inverters and a double-touch capacitor, also called "supercapacitor", placed either above the rotary engine or between the cylinders for a "V" engine. These capacitors supply the two small electric motors positioned on each of the two front wheel hubs. The 120 V set allows “To generate the same torque as a larger motor operating at a lower voltage”.
The advantage of the capacitor is its ability to store and release electrical energy faster than a lithium-ion battery. Thanks to the greater energy regeneration – when braking – on the front axle, the recovered energy is stored in the capacitors to be used during the next acceleration.
On the patent, capacitors and battery are smart health connected: when the capacitors are full, the recovery overflow is then stored in the battery. It can also recharge the capacitors when they are flat and thus supply the two electric motors – a speed sensor determines when the latter can come into action.
On the other hand, although lighter than a lithium-ion battery, the capacitors have the disadvantage of not being able to store energy indefinitely.
A future RX-9?
Seen like that, this system seems complex. However, it has the advantage of combining hybridization and all-wheel drive for a much lower weight than a conventional system. However, there is the question of transposition into production vehicles. We are thinking in particular of the next Mazda 6 sedan or CX-9 SUV. Besides the cost, there are the WLTP standards, which the Wankel rotary motor will have to comply with.
On the other hand, our colleagues from Motor Trend believes that “The development of a rotary hybrid system with three e-AWD engines seems less eccentric” that it seems. It could easily take place in a future RX-9, replacing the RX-8, based on the design of the RX-Vision.
Presented at the Tokyo Motor Show in 2015, this concept car, voted “Most beautiful Concept car” at the International Automobile Festival in Paris in 2016, is a vision of the sports car of the future with a Wankel rotary engine.
We keep our fingers crossed that such a project can be carried out even if Mazda officials did not wish to comment.
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