Scania Turbocompound
Turbocompounding converts excess energy into power.
Turbocompounding seems to defeat the laws of physics by creating energy out of nothing. It works by recovering energy that would otherwise be lost, or wasted. It is a classic example of recycling. Instead of expelling excess energy via the exhaust pipe, additional heat is extracted from the exhaust gases by a second exhaust turbine downstream from the turbocharger.
The second turbo (the turbocompound turbine) spins at 55,000 r/min. This motion is passed through turbine gears and a hydraulic coupling, then through the timing gears to the crankshaft. Stepping down the revs produces a useful boost in torque, which adds momentum when it reaches the flywheel. This means extra driving force without increased expenditure of fuel.