Electric motors can improve the fuel efficiency of a car--even if they're not driving the wheels.

Using electric power to run accessories like power steering lets engineers remove power-sapping accessory drives from engines--and soon, it will even help those engines produce more power from combustion as well.

The next-generation Audi Q7 SUV will introduce an electric turbocharger, Australia's Drive has reported.

Audi head of diesel-engine development Ulrich Weiss confirmed that the German carmaker will put this technology--called "e-boost"--into production "very soon," possibly in time for the new Q7's expected debut at the 2014 Paris Auto Show this September.

Audi RS 5 TDI concept

Audi RS 5 TDI concept

Previewed recently on a prototype RS 5 coupe equipped with Audi's 3.0-liter TDI V-6 turbodiesel, the system uses an electric motor rather than the flow of exhaust gases into a turbine to spool up a turbocharger.

Since the electric motor brings the turbo up to speed much quicker than exhaust gas flowing into the turbine can, Audi believes e-boost can help eliminate the "turbo lag" associated with these engines.

In the RS 5, the electric turbocharger was used at engine speeds up to 3000 rpm to help spool up a larger, conventional turbo. It was bypassed at higher speeds, as Audi engineers determined that above that level, the electric motor alone was less efficient than using the pressure of the exhaust gases.

In addition to creating a more responsive engine for a potential performance car, Audi's e-boost system could have many fuel-economy benefits.

A lag-free turbo could help a car produce more low-end power--meaning drivers may be less likely to venture further up in the rev range--and use more fuel.

An engine with ample low-end grunt would also require fewer fuel-sapping downshifts to lower gears when more acceleration is needed at highway speeds.

But an electric turbocharger isn't the only expected green feature of the next Audi Q7; alongside the inevitable TDI diesel model, Audi is expected to launch a plug-in hybrid version of the Q7 as well, which will likely share a powertrain not only with its A6 and A8 sedan plug-ins, but also with the upcoming Bentley sport-utility vehicle.


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