Photo: Mazda
I recently sold my plug-in hybrid. Although the BMW 225xe was the best car I have ever owned by a wide margin, it had a ridiculous EV range: only 25 kilometers (15.5 miles) – or so said the onboard computer. I suspect it was less than that. When I'll buy a new PHEV, I want it to offer more electric-only range. At the same time, I do not wish to wait for fast charging or plan to do that with a battery pack that costs a fortune. That’s why I was really anxious to see the MX-30 with a rotary engine. Sadly, Mazda blew it.
I have seen some articles saying that Mazda was stupid for turning a rotary engine into a generator. For the people who wrote these texts, the fun with these machines is to hear them rev high and power the wheels. They totally missed the point. Mazda’s strategy with the rotary engine was brilliant – at least before it wasted it by cutting an already small battery pack in half.
The only company to propose anything remotely similar to what Mazda did was Obrist. The Austrian startup developed the Zero Vibration Generator, or ZVG, a small engine that it created solely to generate electricity. It also modified a Tesla Model 3 to use a tiny 17.3-kWh battery pack. Obrist never disclosed how far the car could travel only with the electricity that component can deliver, but we can try to calculate it.
With a fully charged battery pack and a topped-up fuel tank, the Obrist Mark II prototype would have a 1,500-km (932-mi) range. With a depleted battery pack, the Austrian company said it could travel 700 km (435 mi) at highway speeds. That could lead us to imagine it could travel 800 km, but it would imply the vehicle demanded only 2.16 kWh/100 km, or 46.2 km/kWh (28.7 mi/kWh). That is something that not even the Lightyear 0 can offer as the world’s most efficient four-wheeled vehicle. The Dutch solar car can run 710 km (440 mi) with a 60 kWh battery pack, which means it can deliver 11.8 km/kWh (7.3 mi/kWh). Summing up, the Obrist Mark II’s electric range is lower than that.
The Austrian company gave us another clue about the prototype’s range: it spends 7 kWh/100 km or runs 14.3 km/kWh (8.9 mi/kWh). Multiply that by 17.3 kWh, and you’ll get 247.4 km (153.7 mi). The prototype achieves those numbers thanks to low mass and good aerodynamics, but Obrist said a Model 3 with this strategy could cost €20,000 instead of the €46,700 it did when I talked to the company.
If you know the MX-30 e-Skyactiv R-EV has a 17.8-kWh battery pack, it will seem that Mazda followed Obrist’s formula almost entirely, but there are crucial differences. The first one is that the MX-30 EV – powered solely by its 35.5-kWh battery pack – does not hand out as much mileage as the Obrist Mark II with half the battery pack the Japanese EV has. Its WLTP range is 200 km (124 mi) in Europe. The EPA test cycle grants it even less range: 100 mi (160 km).
That has to do with aerodynamics, weight, and probably also how efficient the electric motor is, but I’d bet more on aerodynamics. The MX-30 has a larger frontal area than the Model 3. In other words, it makes more effort to move at any given speed compared to the Tesla. That alone should have made Mazda realize it needs a bigger battery pack. For it to have the same performance as the Obrist Mark II, it should have kept the 35.5-kWh component.
The deal with turning the rotary engine into a generator is that it is much smaller and lighter than reciprocating mills. MX-30 EV owners who popped up the hood saw there was plenty of room there to put the rotary engine. The issue would be where to put the fuel tank.
Images released by Mazda show it was placed under the rear seats, as it is in most combustion-engined vehicles. A good chunk of the 35.5-kWh battery pack in the MX-30 is also placed there, with the component being taller in that area. The question is why Mazda used all of it to have a 50-liter fuel tank in an electric car.
My old 225xe had a fuel tank of 36 liters (9.5 gallons), and it already had a great total range despite the lousy one provided by its 7.6-kWh (5.8 kWh of usable capacity) battery pack. Depending on how efficient the rotary engine is, that may offer an impressive range to the electric car – even if the company not bragging about that makes it look like the mill is not exactly frugal. Anyway, that is not the point.
Mazda could have given the MX-30 R-EV a smaller fuel tank and a larger battery capacity. Traveling 85 km (52.8 mi) with electricity may make it necessary to burn gasoline more often than it should. Volkswagen promised to offer 100 km in the new Tiguan PHEV. The BYD Destroyer 05 already offers 120 km (75 mi) of range with a battery pack slightly larger than that of the MX-30 R-EV: 18.3 kWh.
If the Japanese carmaker reduced the battery pack to make the MX-30 R-EV cheaper than the electric derivative, that could make sense. However, I doubt that Mazda will manage to sell it for €20,000, as Obrist said its HyperHybrid system could make the Model 3 cost. In the end, the rotary engine will just deliver a reasonable PHEV when it could offer one of the best such vehicles around. I’m still trying to understand what Mazda tried to accomplish with this car, and I do not doubt the Japanese carmaker is also baking its noodles with the same question. Neither of us may ever have an answer for that.
The only company to propose anything remotely similar to what Mazda did was Obrist. The Austrian startup developed the Zero Vibration Generator, or ZVG, a small engine that it created solely to generate electricity. It also modified a Tesla Model 3 to use a tiny 17.3-kWh battery pack. Obrist never disclosed how far the car could travel only with the electricity that component can deliver, but we can try to calculate it.
With a fully charged battery pack and a topped-up fuel tank, the Obrist Mark II prototype would have a 1,500-km (932-mi) range. With a depleted battery pack, the Austrian company said it could travel 700 km (435 mi) at highway speeds. That could lead us to imagine it could travel 800 km, but it would imply the vehicle demanded only 2.16 kWh/100 km, or 46.2 km/kWh (28.7 mi/kWh). That is something that not even the Lightyear 0 can offer as the world’s most efficient four-wheeled vehicle. The Dutch solar car can run 710 km (440 mi) with a 60 kWh battery pack, which means it can deliver 11.8 km/kWh (7.3 mi/kWh). Summing up, the Obrist Mark II’s electric range is lower than that.
The Austrian company gave us another clue about the prototype’s range: it spends 7 kWh/100 km or runs 14.3 km/kWh (8.9 mi/kWh). Multiply that by 17.3 kWh, and you’ll get 247.4 km (153.7 mi). The prototype achieves those numbers thanks to low mass and good aerodynamics, but Obrist said a Model 3 with this strategy could cost €20,000 instead of the €46,700 it did when I talked to the company.
If you know the MX-30 e-Skyactiv R-EV has a 17.8-kWh battery pack, it will seem that Mazda followed Obrist’s formula almost entirely, but there are crucial differences. The first one is that the MX-30 EV – powered solely by its 35.5-kWh battery pack – does not hand out as much mileage as the Obrist Mark II with half the battery pack the Japanese EV has. Its WLTP range is 200 km (124 mi) in Europe. The EPA test cycle grants it even less range: 100 mi (160 km).
That has to do with aerodynamics, weight, and probably also how efficient the electric motor is, but I’d bet more on aerodynamics. The MX-30 has a larger frontal area than the Model 3. In other words, it makes more effort to move at any given speed compared to the Tesla. That alone should have made Mazda realize it needs a bigger battery pack. For it to have the same performance as the Obrist Mark II, it should have kept the 35.5-kWh component.
The deal with turning the rotary engine into a generator is that it is much smaller and lighter than reciprocating mills. MX-30 EV owners who popped up the hood saw there was plenty of room there to put the rotary engine. The issue would be where to put the fuel tank.
Images released by Mazda show it was placed under the rear seats, as it is in most combustion-engined vehicles. A good chunk of the 35.5-kWh battery pack in the MX-30 is also placed there, with the component being taller in that area. The question is why Mazda used all of it to have a 50-liter fuel tank in an electric car.
My old 225xe had a fuel tank of 36 liters (9.5 gallons), and it already had a great total range despite the lousy one provided by its 7.6-kWh (5.8 kWh of usable capacity) battery pack. Depending on how efficient the rotary engine is, that may offer an impressive range to the electric car – even if the company not bragging about that makes it look like the mill is not exactly frugal. Anyway, that is not the point.
Mazda could have given the MX-30 R-EV a smaller fuel tank and a larger battery capacity. Traveling 85 km (52.8 mi) with electricity may make it necessary to burn gasoline more often than it should. Volkswagen promised to offer 100 km in the new Tiguan PHEV. The BYD Destroyer 05 already offers 120 km (75 mi) of range with a battery pack slightly larger than that of the MX-30 R-EV: 18.3 kWh.
If the Japanese carmaker reduced the battery pack to make the MX-30 R-EV cheaper than the electric derivative, that could make sense. However, I doubt that Mazda will manage to sell it for €20,000, as Obrist said its HyperHybrid system could make the Model 3 cost. In the end, the rotary engine will just deliver a reasonable PHEV when it could offer one of the best such vehicles around. I’m still trying to understand what Mazda tried to accomplish with this car, and I do not doubt the Japanese carmaker is also baking its noodles with the same question. Neither of us may ever have an answer for that.
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