Jay Leno's Garage

By Jay Leno
Published in the January 2008 issue of Popular Mechanics.

When I hear people blaming the automobile for global warming, I have to chuckle. At the turn of the previous century, the car was seen as a savior. Back then, horses were the primary means of motive power, pulling heavy carts and carrying people. Sadly, they would drop dead in the streets from sheer exhaustion or abuse. And mounds of manure befouled Chicago, New York and other big cities, spreading nasty diseases like dysentery. Suddenly, the automobile came along and people said, "Oh look, there's just a little blue smoke! How nice." Soon, horses were no longer misused as draft animals and the amount of droppings lying around was significantly reduced. Everyone was happy.

Today, the automobile is under attack from people who believe that it's the major cause of all our environmental woes. But it's not the car. It's the fuel. The residual gases, mainly CO2, produced from burning fossil fuel in internal-combustion engines are to blame. Fortunately, many modern cars don't have to run on fossil fuels.

While most automakers are experimenting with potential solutions, such as hybrids and electric cars, that would drastically change the automotive landscape, BMW is pursuing a simpler solution: Use hydrogen to power a good old internal-combustion engine.

Think about it. Modern IC engines run smoothly, they're powerful and, if they're not 100 percent dependable, they're darn close to it. So why push this technology to the side and start over again with, say, a hybrid or electric car?

I recently spent 10 days driving around in BMW's Hydrogen 7, a standard 7 Series sedan equipped with a 6.0-liter V12 engine that's been modified to run on either gasoline or hydrogen. Unlike a fuel cell vehicle that converts H2 to electricity, the 7 actually burns it just like gasoline. The hydrogen is stored as a supercooled liquid in an insulated tank located behind the rear passenger seats. (The tank is so well-insulated that if you put a scalding cup of coffee in there in mid-September, it would still burn your lips at Thanksgiving dinner!) All that insulation keeps most of the hydrogen at a chilly minus 423 F. But a small amount of H2 is constantly "boiling off," or vaporizing. When the car is not running, the excess gas is mixed with oxygen and vented into the atmosphere. When the car is running, that excess vapor is forced into the vehicle's intake manifold, where it's mixed with air and injected into the engine's cylinders to be burned.

Re-engineering the stock 7 Series engine to handle the combustion characteristics of hydrogen, which burns faster, hotter and more aggressively than gasoline, didn't require extraordinary retrofitting. In addition to a new fuel injection system, the automaker designed special pistons with cooling channels to withstand high temperatures. It also modified the valve seats to deal with the fact that hydrogen gas, unlike gasoline, doesn't contain carbon, which typically helps to lubricate the valves. The Bimmer also senses when it's under hydrogen power and modifies ignition and valve timing. In gas mode, everything returns to normal. So if you handed the keys to someone who had no car knowledge, they'd have no idea they were driving something unique. Now, that's truly a flex-fuel application.