Another interesting technology that we see in racing (F1), but haven't yet seen in a road car (although we probably will) is driving the turbo directly with rec

Another interesting technology that we see in racing (F1), but haven't yet seen in a road car (although we probably will) is driving the turbo directly with recovered electrical energy. Volvo is driving a third turbine, which works, but it's not as efficient as simply spinning the turbine directly with an electrical motor assist. The reason they don't do this is that exhaust powered turbochargers are a real motherfucker of an environment. Excuse the language, but they really are. A turbocharger glows red-hot when generating boost. Putting an electric motor anywhere near them requires lots of advanced materials science and engineering. A turbocharger has two main parts: a turbine that is powered by exhaust energy, and a compressor that pressurizes the intake manifold. Volumetrically, these two are separate. They are connected mechanically by a shaft that runs between the turbine and the compressor. This shaft is, traditionally, only a few inches long, and has some pretty sophisticated lubrication systems. Mercedes went all crazy with their F1 engine and spaced the turbine and compressor apart. Way apart. On opposite ends of the engine apart. This is crazy when you consider how fast a turbo spins. It's not unusual for them to exceed 100,000 RPM. The shaft must be lubricated and extremely well balanced. The benefit of this arrangement is that the compressor is not exposed to the heat of the turbine. As I alluded to earlier, the KERS system in an F1 car can drive the turbocharger directly using electrical energy that is recovered during braking. Spacing the turbine away from the compressor affords the perfect opportunity to save the life of your electrical motor that drives said turbo. The hope is (and it always is) that this technology will trickle down to road cars. Volvo appears to be taking the first step, albeit with a compromise.