To improve the range of the MX-30, Mazda decided to install a rotary engine as a generator. Thus was born the Mazda MX-30 R-EV. A good solution ?
There are several ways to view the electric car. The first, and by far the easiest, is to recharge the battery with an external power source. This is the very principle of electricity as we know it. But the manufacturers quickly imagined another more philosophical solution with the range extender. This system is characterized by the presence of a heat engine which acts as an energy generator and supplies the battery in real time. In all cases (except hacks as was the case with the Opel Ampera), the heat engine is not connected to the wheels and only the electric machine moves the car forward. However, the name of this technology can be misleading. Because even if the car advances on the sole power of electricity, it is no longer an electric vehicle in the eyes of the administration and switches to the hybrid segment. Which is perfectly consistent with the real technical name of this technology, called hybrid-series.
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Most of the time, it is a modest mechanism that is used to generate electricity. This must be as economical as possible, of course, and its power level does not really matter to the driver since the engine does not drive the wheels. The BMW i3 Rex featured a 650cc from scooter manufacturer Kymco. The Note e-Power, the first to embed this technology at Nissan, was based on a 3-cylinder 1.2 l atmospheric. A far cry from the new variable compression ratio turbo engine (code KR15) of the Nissan Qashqai and X-Trail e-Power, which takes up space under the hood due to its technologies.
Now, this exotic branch in the hybrid vehicle segment has a new member: the Mazda MX-30 R-EV. The opportunity for the Hiroshima firm to reconnect with the old knowledge that is the famous rotary engine. Compact, simple, powerful and vibration-free, it looks like the ideal thermal generator on paper. Still, if it seduces technically, it does not seem to revolutionize the system, which has already had a few attempts like the Audi A1 e-tron of 2010 for example, also with a rotary engine.
A new 8C rotary for the Mazda MX-30 R-EV
The operation is broadly identical: the heat engine drives a generator which produces the current to recharge the battery, the latter thus supplying the electric machine mechanically connected to the front wheels. The heat engine is therefore the part of the system that interests us today. Responding to the code name 8C, it is a single rotor with a displacement of 830 cm3 which has been completely redesigned. The rotor has a radius of 120 mm and a thickness of 76 mm. The segments are 2.5 mm thick to improve their longevity and overall reliability. Still in terms of construction, the aluminum block allows the engine to claim 15 kg less compared to the Renesis birotor of the Mazda RX-8.
Like all rotary engines, this engine is very compact and therefore does not take up much space under the hood of the MX-30. It was thus attached to the generator and the electric machine to form a single block 84 cm wide. Enough to save space on the hood of the SUV according to the manufacturer. But it is worth remembering that the engine bay did not really impose a very big technical challenge: the MX-30 is also available in Japan with a much larger Skyactiv-G heat engine.
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The manufacturer specifies that the walls of the chambers have undergone a plasma surface treatment to reduce internal friction. Added to this is direct injection (a first for a series rotary) and a gas recirculation system to improve efficiency, control fuel consumption and reduce emissions. Finally, the compression ratio of 11.9:1 is a little higher than on ordinary engines (efficiency is favored to the detriment of power), but does not reach the ratio of the e-Power system (until ‘at 14:1) for example.
With 74 hp at 4,700 rpm for 116 Nm of torque at 4,000 rpm, the thermal engine displays modest values. As usual with this rotary piston engine, the torque does not panic the counters. But it should be available sooner than with a traditional engine. This should be sufficient for the requested missions. In addition, this block also has the advantage of offering better efficiency and more optimal rotation speeds. According to the manufacturer, it will be able to turn between 2,450 and 4,500 rpm. A desire to create a better correlation between engine speed and driving pace.
A CX-60 PHEV battery
As you have understood, this motor therefore acts as a generator to supply the traction battery. This goes from 35.5 kWh on the 100% electric version to 17.8 kWh. A much more generous unit than the 1.9 kWh used by the e-Power system. Above all, that of the Mazda is rechargeable in alternating current (11 kW) or direct current (35 kW). Enough to refuel in about 50 or 25 minutes respectively. Mazda did not specify the exact origin of the battery, but it is not the unit of the MX-30 EV scalped by a few cells. Its dimensions had to be revised to make room for the 50-litre tank. It could probably be a rearranged version of the Mazda CX-60 PHEV battery: the total capacity of 17.8 kWh and the voltage of 355 V are strictly identical. Which means that the total cell capacity is 50 aH.
This battery, whose output power we do not know, then powers an electric machine with a maximum power of 170 hp (125 kW) for 260 Nm of torque. By being in direct drive to the front wheels, these are its values which appear on the technical sheet. However, this does not mean that the battery can supply the machine with full power. Surely there is a gap that the rotary engine will have to fill. This will be the case in Normal driving mode, where it will take over automatically. Depending on the power demand, it can directly supply the electric machine via the generator. In EV mode performance should be lower. Finally, in Recharge mode, the 8C block will take care of recharging the battery. A nonsense in a plug-in hybrid vehicle, all the more equipped with a fast charging system.
Consumption that promises to be very high
All this therefore has only one goal: to offer even more autonomy to the Mazda MX-30 (which is sorely lacking in the electric version) while controlling consumption as well as possible. Side pure electric autonomy, Mazda announces a mixed value of 85 km. By combining the two energy sources, the SUV claims 600 km of autonomy in total. We do not yet have the details of the hybrid operation, but it clearly appears that the electric and thermal autonomy have been added. A quick calculation without scratching your head too much then indicates a consumption of 9.7 l/100 km. Or 8.3 l/100 if we stupidly take all autonomy into account. In short, consumption should oscillate in these waters. But surely more with a battery on its available charging base!
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Here’s what to expect when using the SUV in Normal mode. Only the frequency of the electrical evolutions will then make it possible to lower the average. In any case, to reach the WLTP value of 1.0 l/100 km (21 g/km of CO2), it will theoretically be necessary to drive almost 90% of the time in electric mode. In other words: it will be necessary to travel 900 km out of 1,000 km by the sole force of the electric machine… We will not issue hasty conclusions since all the uses are in nature, but the ratio seems difficult to achieve in reality.
Finally, the most precise will remember that if the levels of CO2 and NOx emissions are similar to those of a conventional heat engine, the releases of unburnt hydrocarbons (HC) are much higher. However, studies claim that in the case of a hybrid-series application like here, the HCs would not be “not so high”. A vague conclusion for data that is difficult to verify without very specific measurement tools.
The ideal generator on paper, a little less in use
The Mazda MX-30 R-EV is therefore no longer an electric vehicle as the brochure would like to convey. It is neither more nor less than a plug-in hybrid SUV with an exotic traction chain where only the electric machine drives the wheels. However, this is one of the advantages of the hybrid-series architecture: the immediacy of the machine gives driving pleasure similar to that of an electric car. It remains to forget as best as possible the presence of the heat engine. And that’s what the rotary engine wants to do. Naturally free of vibrations, compact and light, it then has the shape of the perfect generator for this application. And these characteristics there, it has them well.
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But they struggle to show real benefits in absolute terms. Its dimensions do not really benefit the habitability (it does not create a storage space under the hood) and its controlled weight, a guarantee of better autonomy on paper, does not seem to have any effect: with a total of 1,780 kg, the SUV is 130 kg heavier compared to the 100% electric model, and 320 kg compared to the Japanese thermal version! Wanting to save weight with mechanical technology is to be emphasized. But it must not be the tree that hides the forest. Too bad, because with a total mass of 71 kg, it is lighter than the KR15 Nissan and its 125 kg on the scale.
It therefore only has for him the absence of vibrations. But the Yokohama engineers have already shown that the too complex thermal engine of the e-Power system based on specific silent blocks can also effectively suppress vibrations in the structure. It will therefore be necessary to put it to the test of the road to take stock of its actual consumption which, according to our theoretical projections, is expected to be much higher than that of the competition. Moreover, the use of the customers will make it possible to take stock of the technical advances of this engine with rotary piston, sadly famous formerly for the longevity of the seals of the rotor and for its congenital oil consumption, which should have been the object a separate line in the technical data sheets as it has proven to be so important.
Remember that the Mazda MX-30 R-EV is displayed from €38,250 in the Prime Line finish. The Edition R special edition climbs to €45,450. The Kia Niro PHEV, its direct competitor, has a price tag of €39,140 to €43,940, with much more reasonable fuel consumption when it comes to making long journeys on board.
