What is an Electric Turbocharger?

In order to make cars as efficient as possible, automakers are resorting to turbocharging their engines, but a new kind of turbocharger is on the way that could change the game.

“Engine downsizing is one of the key solutions used by carmakers to reduce vehicle fuel consumption,” explains automotive supplier Valeo in a statement. “However, to maintain high performance with a downsized engine, car manufacturers generally use an exhaust-driven turbocharger, which comes with a delayed boost response known as turbo lag.”

That slow response has been plaguing turbocharged cars for years and is a common complaint. Things like twin-scroll turbochargers or smaller turbos are used as a means to combat lag, but it’s still not perfect. Simply put, it’s hard to make a turbocharged engine deliver the immediate response of a naturally aspirated one.

“An electric motor can responds instantly (within 250 milliseconds),” says Valeo. The company says it can reduce fuel consumption by 10 percent using this set-up. Since it’s not exhaust-driven these compressors are technically just a supercharger, but for the sake of simplicity they’re often called electric turbochargers too.

Volkswagen and its associated brands are heavily investing into this electric turbo technology.

“Volkswagen Group is working on the development of electric turbo chargers for its various brands globally,” said Mark Gilles, from VW USA’s technology communications team. “The main advantage is response time and that it supplies boost from idle speed, in comparison with exhaust chargers that require at least 1500 rpm to supply extra pressure.”

Audi has recently shown off its latest developments in the world of electric turbos with the Clubsport TT Turbo Concept, an all-wheel drive car that puts out 600 hp and 479 lb-ft of torque thanks to a pair of turbochargers outfitted to its 2.5-liter five-cylinder engine. One turbo is a traditional exhaust-driven type, while the other is an electric unit.

Audi made the concept to show off the potency of electric turbochargers, saying that the technology is close to being ready for production vehicles. There’s a 48-volt electrical sub-system in the trunk that powers the electric compressor, sending boost to the engine on demand, rather than waiting for the exhaust-driven turbo to spool up. It all adds up to a car that can hit 62 MPH in 3.6 seconds.

“An elec­tri­cally pow­ered com­pres­sor of­fers sig­nif­i­cant ad­van­tages,” said Brad Stertz from Audi USA’s powertrain communications team. “It revs up to max­i­mum rpm rapidly and with­out any per­cep­ti­ble de­lay, and it con­tin­ues to boost charge pres­sure when too lit­tle drive en­ergy is left in the ex­haust gas for the con­ven­tional tur­bocharger.”

“This op­er­at­ing prin­ci­ple makes it pos­si­ble to de­sign the con­ven­tional tur­bocharger more specif­i­cally for high charge pres­sures and con­se­quently for high en­gine power – the e-turbo as­sures spon­ta­neous re­sponse and pow­er­ful sprints from low en­gine speeds at all times,” he added.

It’s not the first time Audi has shown off its expertise with electric turbos either. Last year the German automaker added an electric turbo to its twin-turbo 3.0-liter diesel V6 engine and stuck the whole concoction into a RS5. The result was a blistering fast coupe that could hit 60 MPH in about 4 seconds, all while netting 47 MPG. That makes it faster than the regular RS5 and more than twice as fuel efficient.