Mazda i-Activ AWD uses predictive tech

MAZDA’S rebranded i-Activ all-wheel drive system as found on its SkyActiv models such as the CX-5 and all-new CX-9, uses software technology to improve the effectiveness and efficiency of what is a relatively simple and inexpensive alternative to rival products.

Speaking to GoAuto at the Mazda Ice Academy global media event in Colorado, Mazda Motor Corporation assistant manager for drivetrain and powertrain development Tetsushi Marutani revealed that the goal was to slash torque transfer times, reduce lag, cut weight, and close the consumption gap that exists between two-wheel and all-wheel drives.

“Previously, our all-wheel-drive system was about (increasing) performance only,” he said. “Now our focus has moved to improving efficiency, but still with best-possible performance too.”Essentially the same design in terms of hardware as Mazda’s previous on-demand AWD set-up, introduced with the original Mazda6 in 2002, i-Activ uses advances in software to achieve its desired results.

Mr Tetsushi was also the brains behind the earlier system, and started work on i-Activ when the SkyActiv technologies development started in earnest in Japan during 2007.

There are two versions – a compact one for the CX-3 crossover and Japanese home-market Mazda2/Demio AWD, and a larger and stronger one for vehicles from the CX-5 to CX-9 SUVs.

The big news is that Mazda’s system is predictive. Building on the old system that determined traction loss and then sent torque to whichever wheel needed it according to wheel speed, engine RPM, air/fuel mixture present, gear shift position, and accelerator pedal position, i-Activ now also collates engine, transmission, steering, brake, and prevailing weather data.

More specifically, sensors ‘read’ the car’s steering torque and its electric motor current levels, steering angle, electronic stability control longitudinal g-force readings, ambient temperature, and even if the wipers are activated.

In all, some 27 sensors feed data to a central control module at a rate of 200 times per second, via an Active Torque Control Coupling, which is electromagnetically activated. As these can all be tell-tale evidence that traction loss may be imminent, i-Activ’s software then pre-empts tyre slippage before it happens by sending drive to the wheel that is about to need it.

Mazda says that the upshot of this anticipation tech is more precise and safer control, with the far-faster torque transfer already driving the wheels. And since the inertia of slippage has been mitigated, less torque is required to keep the wheels gripping, thus saving fuel.

Additionally, minute torque levels are constantly fed to the rear wheels so there is no “backlash” when drive does kick in. Seamless operation is the goal.

Mr Marutani said that lag has not yet been totally eliminated, but that the next generation of i-Activ due when the CX-5 is renewed in about two years time will feature even quicker reaction times.

The physical hardware now weighs less (by at least 25kg – the total amount is a secret, but it is believed that the CX-9’s system has dropped from 80kg to 54kg), with the SkyActiv-Drive six-speed automatic transmission featuring a lightweight propeller shaft with a damper that cuts noise, vibration and harshness levels.

Also new is a smaller and lighter rear differential with smaller innards, better cooling properties, a lower-viscosity synthetic oil, and detailed casing improvements to reduce friction. Mazda says the point of the i-Activ’s operation is to be completely invisible to the driver – no lights, no switches, no tyre slipping – so that they won’t even be aware that a potential traction hazard has been avoided or minimised. While most rival on-demand systems from Toyota, Nissan, Honda, Volkswagen and Audi were studied during development, Subaru’s Symmetrical AWD set-up was the benchmark for i-Activ.