Raptoer

Super Efficient Material Converts Car Exhaust to Energy (Switched)

Sep 9th 2008 1:53AM This material uses thallium, which is produced as a side product from trace amounts from smelting other chemicals. It is primarily used in electronics, however it is also quite toxic. I doubt that this material itself is toxic however as it is lead doped with thallium, and would have chemical properties closer to lead (still a heavy metal, but much less toxic).

This idea is a form of cogeneration, already used in large industries, especially power plants. Cogeneration usually increases efficiency from 55% to 89% in power plants. The difficulty with putting these cogeneration facilities into cars is weight and pressure. If the exhaust is significantly slowed down or stopped to be put into some other component it causes problems with the engine.

As for the car itself most engines will get 20-25% efficiency, and the maximum possible (according to the laws of thermodynamics) is 37%.
If you can recover 1% of that energy and put it back into powering the car you increase the fuel efficiency by 4 - 5%.