Even the small battery – used on mild hybrid versions to harvest waste energy from braking and coasting – wouldn’t have to be an expensive and complex lithium ion unit. Instead, it would be a much more stable, less demanding lead-carbon battery.
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A car maker that went down this engineering route would be able to manufacture a single engine in a single size and for a single type of fuel. It might only need to source conventional turbochargers in just two or three different sizes.
For hybrids and the most powerful versions of such an engine, the car maker would need just one type of integrated starter generator (ISG) – which provides an electrical supply for an electric supercharger and recuperates waste energy – and one type of high-speed electric supercharger, which ensures significant torque from tickover.
Such a simple and cost-effective future need not be imagination. Autocar has actually driven it – and, yes, it’s extremely impressive.
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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