Why can’t we use the heat from combustion to make cars more efficient?

Question

Can we use the heat to boil water to turn a turbine? Or would the water never cool enough to be used again?

What about using the heat to create pressure and then releasing the pressure to help move the fly wheel?

In: 1046

Answer 1

At the extreme end of performance vehicles, they do capture exhaust heat and store it as electrical energy to power hybrid electric motors. See https://en.m.wikipedia.org/wiki/Porsche_919_Hybrid
I imagine this is too expensive to be used in standard production vehicle.