Read the following article from FastCompany Mag. The magazine article with pictures is even better. This guy also talks about the hummer getting 60mpg and 0-60 in 5 seconds.
This is more than a mere American Chopper--style makeover. Goodwin's experiments point to a radically cleaner and cheaper future for the American car. The numbers are simple: With a $5,000 bolt-on kit he co-engineered--the poor man's version of a Goodwin conversion--he can immediately transform any diesel vehicle to burn 50% less fuel and produce 80% fewer emissions. On a full-size gas-guzzler, he figures the kit earns its money back in about a year--or, on a regular car, two--while hitting an emissions target from the outset that's more stringent than any regulation we're likely to see in our lifetime. "Johnathan's in a league of his own," says Martin Tobias, CEO of Imperium Renewables, the nation's largest producer of biodiesel. "Nobody out there is doing experiments like he is."