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How all-wheel drive cars could use less fuel than 2WD

By Toby Hagon, 04 Feb 2016 News

How all-wheel drive cars could use less fuel than 2WD

Mazda says it is developing super-efficient four-wheel drive vehicles

The days of two-wheel drive SUVs could be numbered if car makers can take away one of the biggest factors limiting their all-wheel drive siblings – high fuel use.

Mazda says it is close to developing a four-wheel drive system that is more efficient and uses less fuel than a lighter two-wheel drive system.

Speaking at the inaugural Mazda Ice Academy – a snow and ice driving course designed to highlight advantages of the brand’s i-Activ all-wheel drive system – drivetrain assistant management engineer Tetsushi Marutani said Mazda’s goal was to have an efficient four-wheel drive system “in the near future”.

“Our goal is to beat the 2WD efficiency on dry pavement,” said Marutani, adding that the second generation of i-Activ all-wheel drive wasn’t far off.

“If we get zero mechanical loss on mechanical system … we can beat 2WD [for efficiency].”

Mazda engineers point to inherent mild wheel slip by the powered wheels in any vehicle as a small but significant source of energy loss that can be reduced by powering all four wheels.

While i-Activ predominantly drives the front wheels when traction is good, they say that spreading some of the drive to the rear wheels will reduce those losses.

With pending improvements as part of the second generation i-Activ all-wheel drive system, Marutani says the benefits will outweigh the energy used to drive the AWD mechanical components.

“We are developing a new i-Activ AWD to reduce losses,” he said.

As for the additional weight of a four-wheel drive system – typically upwards of 50kg due to additional differentials and driveshafts – Marutani says it is negligible and will be outweighed by the reduction of wheel slippage in regular driving.

Mazda claims its i-Activ all-wheel drive system is more advanced than most on-demand systems used in car-based SUVs. It uses 27 existing sensors and systems in the car – everything from windscreen wipers and the external temperature to road speed, steering angle, g-forces and braking force – to predict when additional traction is required.

Mazda says the system can accurately predict low grip surfaces and bring all four wheels into play before wheelspin occurs, for smoother activation and added confidence.