Electric turbocharger eliminates lag, Valeo says

Electric turbocharger eliminates lag, Valeo says

French supplier Valeo has developed an electric turbocharger that it says eliminates “turbo lag.” The new turbocharger is powered by an electric motor instead of exhaust gases.

When not needed, the turbo’s impeller, which pumps air and fuel into the cylinders, still spins at 10,000 rpm, so there is minimal hesitation or lag in engine response when the driver presses the accelerator pedal.

But there are downsides: cost and power consumption. The unit requires 48-volt power, which means additional electronics under the hood. It also is a heavy user of electricity. Still, automakers are intrigued.

Audi has been testing the electric turbocharger and is expected to be first to market the device. It recently tested the turbocharger on Pikes Peak in Colorado.

Audi r&d chief Ulrich Hackenberg hints at equippingproduction cars with both electric turbochargers and standard turbochargers powered by exhaust gases. They could come to market by 2016, he said.

Mercedes-Benz r&d chief Thomas Weber says the technology is “relevant” and a “valid option” when mated to 48-volt or higher voltage systems.

“It is a real alternative to two-stage turbocharging,” he said.

Two-stage turbos use two fans — one for low speeds, another for high speeds.

BMW engine development manager Nikolai Ardey says the company is studying the technology but is looking at alternatives as well.

A powertrain expert at General Motors described the technology as “very interesting” and “under study.”

Valeo says the electric turbo-charger can reduce fuel consumption by between 7 and 20 percent.

Curt Estes, Valeo’s regional operations director of powertrain systems, said 20 percent reduction is possible when the device is used on a vehicle equipped with regenerative braking, which captures the car’s kinetic energy and turns it into electricity.

Valeo calls the device an electric supercharger. But a supercharger is driven mechanically by the engine and uses rotors rather than an impeller to pressurize the engine’s cylinders.
Ever since GM pioneered the use of the turbocharger on a regular production car with the 1962 Chevrolet Corvair, engineers have been improving the device.

Packing more fuel and air into the cylinders enables the engine to increase its power output. But the turbocharger’s drawback is that the engine has to work harder to expel exhaust gases. And there is usually a lag between the time the turbocharger spools up and when the driver feels the rush of the additional power.

Valeo’s Estes says the powerful electric motor can spool up the impeller to 70,000 rpm in less than a second, which eliminates turbo lag.

It is mounted close to the engine’s intake manifold.