It's a turbocharged hybrid engine with two electric motor-generator units. One on the shaft between the turbine and the compressor and the other is on the crank

It's a turbocharged hybrid engine with two electric motor-generator units. One on the shaft between the turbine and the compressor and the other is on the crankshaft. Excess heat energy is captured from the turbo with the generator instead of blowing the excess out of the waste gate. The turbo is pre-spooled by turning it with the electric motor so the internal combustion engine runs at or near stoichiometric optimal fuel-air mix at all times. The other motor generator does regenerative braking and can drive the engine. The Mercedes engine is rumored to develop around 950 horsepower from the 1.6l V6 engine (of which about 160 are from the electric motors). I'm hopeful that similar technology will find its way to road cars. City buses in particular would benefit a lot due to frequent stops.