The scalable technology that could save the combustion engine

Mahle Powertrain, part of a global group, is based in Northampton and was born out of the old Cosworth operation. Mahle’s UK engineers have built a Volkswagen Golf GTI prototype – the ‘eSupercharged Downsizing Demonstrator’ – based around the company’s unique threecylinder, 48V mild hybrid powertrain.

We’ve seen similar prototype downsized powertrains, but the big difference with Mahle’s set-up is a new high-speed electric supercharger that provides the low-down thrust until the big, conventional turbocharger takes over.

Made by Aeristech, it is powered by the Golf’s new 48V electrical system and spins at between 5000rpm and 120,000rpm. The company says this eSupercharger differs from existing electric superchargers in that it can run for extended periods of time. Current prototype electric superchargers, they say, are used for filling in torque curves at lower speeds and run for only a matter of seconds at a time.

Road legal and tested in Mahle’s own labs, this boosted 1.2-litre unit is claimed by the company to produce 260bhp, which is 216bhp per litre, a figure far in excess of any current production car’s engine.

The powerplant also delivers 232lb ft from 1500rpm. Mahle’s charts claim that more than 80% of that torque is available from 1000rpm and, according to the dyno figures, the torque output holds up all the way to 4500rpm.

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But the main point of this technology demonstrator is to show that a high-performance engine can deliver significant fuel economy savings in normal driving conditions. Mahle says this engine should return around 57.5mpg on the standard European test regime while still meeting the upcoming EU6c pollution regulations. That’s nearly 25% better than the standard-issue current Golf GTI.

My first attempt to sample the Mahle Golf on the track is hobbled by the fact that the eSupercharger refuses to spool up much beyond its own tickover. However, it does give me the chance to try out this tiny engine with only the big, conventional turbo. A few laps of the track make it clear that this engine feels all but production ready. It’s smooth and refined and has proper, rock-steady push once the big turbo is spooled up.

A couple of weeks later I’m back to try a revitalised car with the eSupercharger working properly. After 15 minutes at Bruntingthorpe airfield, my conclusion is pretty straightforward: this is a very impressive piece of engineering.

Perhaps the best way to describe this motor’s character is as a pintsized V6. The engine’s tractability as soon as the car is rolling is marked. The eSupercharger means this tiny engine, at low speeds, does a nearperfect impression of a deep-lunged, big-capacity motor.