Building an Electric Supercar at Home

By Wesley Fenlon

Twice the horsepower of the Tesla Model S in a 1970s BMW? You've got our attention.

Tesla's Model S accomplished a goal that has eluded carmakers for decades. It's an electric car with no sacrifices in design: Even without a combustion engine, it can hit a top speed of 125 miles per hour and accelerates to 60 in five seconds. It looks like a real luxury sedan--no funky solar panels like the electric cars of the 90s, no cramped interior like the diminutive Smart car. The performance model of the Tesla offers around 400 horsepower. Beastly for a sedan--but only half of the power Californian Mike Pethel has built into a homegrown electric BMW.

Pethel's building an electric BWM supercar. He wants it to be the fastest environmentally friendly car on the road. It likely already is, and he hasn't even put the finishing touches on yet. Marketplace describes Pethel as an obsessive, but also a bit of a genius.

"In the months I've watched the project, I've come to think his real goal is innovation itself -- rethinking cars," writes Alex Chadwick. He's developed new motors; they can run a racecar or a bread truck, he says -- it's all in the tweaks. This from a no-college techno-savant turned radical green."

The pair of electric motors under the hood of Pethel's modified BMW run on DC, direct current, rather than the more common alternating current. And it's not built for efficiency--the car can only travel about 50 miles, a third of the Model S' baseline 160 miles (and far shorter than its 300 mile maximum). But it can burn through a megawatt of energy, which Marketplace calls enough to power 750 homes.

And that raises a question about how environmentally friendly the car is, exactly. Does it burn fossil fuels by itself while it's tearing down the highway? No. But that's a technicality, and Pethel's BMW clearly uses a monstrous amount of energy to earn its supercar stripes. On the bright side, the engine doesn't have to burn up a suburb's worth of electricity to run.

Pethel says he could build a 200 horsepower model or a 2000 horsepower model. In time, his engine could compete with the Tesla or the Nissan Leaf or the Chevy Volt. Not bad for a guy with no college education.