Life in the fast lane to the future is sweet when you're behind the wheel of Honda's latest experimental fuel-cell sedan. During my six-lap attack of the company's banked oval in Tochigi, Japan, I made the FCX's tires howl with aggressive cornering and braking, bumped up against its 94-mph speed limiter, and broke the ten-second barrier accelerating from rest to 60 mph. All this occurred while depositing nothing more noxious in my wake than traces of tire dust and wisps of water vapor.

Unlike other hydrogen-powered prototypes, this one barely murmurs. Even though the FCX has been running for only three months, its electro-chemical-mechanical soul is already rid of gear whine, motor hum, and relay clicks. All I heard was tread swish, wind ruffle, and a soft growl that intensified as I legged the accelerator. According to my copilot, chief engineer Kenichiro Kimura, the growling sound is the Lysholm-type compressor force-feeding air to the fuel cell.

But the breakthrough here isn't that the FCX is clean and runs quietly. All fuel-cell vehicles claim that. What Honda has achieved is the first zero-pollution sedan that bears no resemblance to a minivan packed full of science fair leftovers. The FCX's futuristic Toyota Prius-plus shape is enabled by two breakthroughs: an ultracompact electric drive system and a fuel cell turned on its side to fit within the FCX's console.

A 127-hp, alternating-current motor lies coaxially with a single-speed transaxle to minimize the volume and weight of the propulsion gear. The half-shaft to the right front wheel passes through--instead of behind--the motor, an arrangement not possible in today's crankshaft-driven cars. This arrangement trims 6.4 inches from the drive system's length, maximizing legroom and shortening the front overhang.

Honda's clever vertical-stack fuel cell is 20 percent smaller, 30 percent lighter, and 16 percent more powerful than the previous-generation FCX's cell. A box only twice the size of a desktop computer produces 100 kW (134 hp) of electrical power. Low-volume production will commence in 2008.