Born-again Mazda super-coupe to pack 350kW turbo-hybrid HCCI rotary, transaxle and sub-1400kg mass

Mazda finally came clean on its intentions to deliver a new-generation rotary sports coupe by revealing the stunning RX VISION concept at last month’s Tokyo motor show.

But since Mazda executives remain tight-lipped about what we’ll find under the bonnet of the Hiroshima car-maker’s show-stopping supercar, the big question remains: what kind of rotary power will we see in the all-new ‘RX-9’?

“You will have to wait until 2017 to find out what will power this car,” said a Mazda executive. “That’s our rotary’s 50th anniversary year.”

We do know that the new coupe will employ ‘SKYACTIV-R’ technology, which is Mazda-speak for a totally new rotary powertrain.

Rather than a revised version of the 1.3-litre 13B Renesis rotary from the discontinued RX-8, however, the new car will be powered by an all-new rotary already previewed by the larger, twin-rotor 1.6-litre 16X concept engine, but that’s all we knew – until now.

A source close to Mazda says that to address the 13B’s thirst, lack of mid-range torque and excessive oil consumption, the company is currently testing a new hybrid turbo rotary engine, which is still referred to as the ‘16X’ and boasts a twin-800cc rotor set-up, but is expected to generate more than 335kW.

What’s more, unlike the MX-5, it will drive its rear wheels via rear transaxle. As with all proper supercars, this means the transmission — most probably a dual-clutch configuration — will be integrated into the rear axle to improve weight distribution.

We’ve also heard Mazda engineers are working on a two-stage turbo system incorporating an “electric turbo assist” function that engages at low rpm, and a standard exhaust-driven turbo that cuts in at higher revs.

The former will be a capacitor-powered e-turbocharger, making it a hybrid powertrain of sorts, using similar technology to the capacitor-based regenerative braking system in the Mazda6 – rather than the rotary range-extending technology seen in the Mazda2 plug-in hybrid concept.

“Engineers will employ a capacitor [a unit that stores power and discharges it on demand] to beef up the rotary’s ‘instability’ at low rpm, and when boost pressure rises, a standard turbocharger will engage to keep the flow of power coming,” said our source.

Contrary to the words of R&D boss Kiyoshi Fujiwara with motoring.com.au last month, Mazda will incorporate HCCI, or homogeneous charge compression ignition – where the fuel/air mixture is compressed to the point of auto-ignition, as in a diesel engine. HCCI engines achieve extremely low levels of nitrogen oxide (NOx) emissions without a catalytic converter.

The same SKYACTIV II technology is expected to be used across the seventh-generation model range from 2017, starting with the next CX-5, to reduce fuel consumption a further 30 per cent over 2015 levels.

Apart from prodigious power and a broad, flat torque curve — both of which should more than double the output of the 170kW/211Nm RX-8 — the unique SKYACTIV-R should spin beyond 8000rpm and be far more efficient than Mazda’s last Wankel mill.

Thanks to generous amounts of aluminum and “several carbon-fibre parts” engineers are now experimenting with, the production coupe – which is expected to be up to 200mm shorter than the rangy concept – is due to land with a kerb weight of less than 1400kg, which should produce Porsche 911-style power-to-weight and performance levels.

Now that the new ND MX-5 is in showrooms, Mazda is believed to have reassigned engineering and design staff from the roadster to the new RX coupe.

But our sources say that, counter to previous rumours, MX-5 chief engineer Nobuhiro Yamamoto will not be leading the rotary’s development and that a younger engineer has been given the job, but just who that is will remain secret for at least another year or so.