[serialk11r]

A turbocharger does NOT act like a heat engine on a car. It will capture some of the excess energy that is the exhaust gases being at higher than atmospheric pressure when the exhaust valve open. This is useful for race cars that are run at WOT most of the time (I read that it boosts efficiency by 7% at WOT) but not for street cars which have very little excess pressure running at 30% load.

Look up BMW Turbosteamer. They were able to generate a consistent few kW from the exhaust with a Rankine cycle generator, 10kW peak. Not a DIY project though.

I imagine in the future as high temperature thermoelectric tech advances we'll be able to get most of the benefit in a simple bolt on package. Thermoelectric generators that are half as efficient as the BMW steam turbine cycle could completely alleviate all accessory loads on the engine and keep a hybrid system's battery topped up.