SANTA BARBARA, California — Mat the accelerator of the 2017 Honda Clarity Fuel Cell and you're propelled into the distance with only a slight whir emanating from an electronic turbo air compressor. It's actually quite remarkable what's happening: Hydrogen and air flow into a fuel cell, which converts the gasses into electricity and heat. The reaction's only by-product is water so pure, you could drink it.

Honda has made a big bet on this propulsion technology, and it shows in the latest incarnation of the company's hydrogen-powered offering. It's a car that has evolved dramatically from a glorified science experiment back in 2008 to one that's potentially on the verge of limited market acceptance.

What's going on under there?

Pop the new Clarity's hood and the setup looks almost like a conventional gasoline engine at first glance. The powertrain is topped by a voltage-control unit that boosts and regulates the electricity created by the hydrogen fuel-cell stack, which is 33-percent smaller than before thanks to cells that are 20-percent thinner (down to a single millimeter per cell). It also uses 30-percent less of them overall compared to the outgoing Clarity's stack. The stack's cells are made from Polytetrafluoroethylene, more commonly known as Teflon. It looks like saran wrap and converts hydrogen and oxygen into water, releasing electricity as it does. The aforementioned air compressor helps boost air to the stack, increasing power in a way similar to a conventional engine turbocharger. Finally, there's the drive unit, which consists of the high output AC synchronized electric motor, transmission, and power control unit. It all fits neatly under the hood and takes up less space than Honda's V-6 gasoline engine.

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Underneath the Clarity's floorpan is a small 1.7kW lithium-ion battery that can store the electricity generated from the stack but mainly helps with regenerative braking and hard acceleration when combined with the fuel-cell stack's full output. Two aluminum lined tanks of different sizes store hydrogen fuel at 10,000 psi, one behind and one under the rear seats. This packaging arrangement helps make the Clarity the first fuel-cell car able to seat five passengers. At 11.8 cubic feet, its trunk space is adequate but somewhat compromised by the tank.

Even better, using fewer cells doesn't mean sacrificing power. The development team managed to squeeze 1.5 times more overall power from the system, an engineering feat that deserves an attaboy-san. Total system output is 175 horsepower and 221 lb-ft of torque. More importantly, the Clarity is EPA rated at 366 miles per fill-up, the farthest range of any zero emissions vehicle. And unlike all-electric vehicles, hydrogen fill-ups are now down to the three-to-five-minute range, comparable to a gasoline-powered car. That is, if you can find somewhere to fill it; hydrogen stations are largely limited to the Los Angeles and San Francisco areas.

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Get flowing

Advanced aerodynamic technologies are used extensively on the 2017 Clarity. Air curtains route air from in front of each wheel arch, passing it around the outside face of the wheel during cruising, helping to reduce drag (Acura employs similar tricks on its NSX supercar). The car's entire underbody is also flat in order to help smooth airflow and decrease drag, more tactics we're used to seeing in supercar and race applications.

Aerodynamicists working with sedans usually have issues with something called vertical vortexes, when the air travelling over the roof of the car travels at a different speed to the air travelling around the side of the car. When they meet at the trunk, turbulence caused by these vortexes creates instability and drag. The Clarity team mitigated this issue by sculpting the rear fenders to match the side-air speed to the roof line. Additionally, small wheel covers that hide the top portion of the rear wheels help to further reduce turbulence.

Cool, quiet cabin

Unlike Toyota's Mirai fuel-cell vehicle, Honda didn't try too hard to be futuristic with the Clarity, but its cabin is trimmed in eco-friendly materials such as recycled "Ultrasuede" and plant-based "Prime-Smooth." It's actually far better than it sounds and is arguably the most sophisticated, refined, and well-upholstered interior in Honda's lineup. The steering wheel is thick and well weighted, and switchgear is what you'd expect from a luxury sedan. The color head-up display contains speed information as well as navigation prompts, and its intuitive infotainment system can be linked to your cell phone through Apple CarPlay or Android Auto.

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Engineers put a lot of effort into reducing interior noise as well. Like EVs, fuel cells are relatively silent in operation and occupants are more likely to notice other squeaks and hums, so Honda deployed a host of insulation and noise-absorption materials including a multi-layered floor carpet and resonators around the wheel rims. The result is a refined and quiet ride.

The Clarity has no options list and comes fully loaded. For $58,490 (though you can only lease one for $369 a month from select dealers in California), you get a host of standard advanced technologies, including road-departure mitigation, lane-keep assist, collision-mitigation braking, and adaptive cruise control.

How does it roll?

We drove a Mirai and Clarity back-to-back, and the differences in philosophy became abundantly clear. While the Honda rides just as comfortably as the Mirai when cruising, it tightens up in the bends, offering more road-holding and instilling confidence when you try to have fun. Chief chassis engineer Yoshihiro Atsumi said, "Our primary goal was to become the number one chassis for this field, and just because the car is eco-friendly, we didn't want it to be boring."

Atsumi-san decided to use an advanced suspension technology called Sensitive Frequency Response Dampers that offers varying damper stiffness without using expensive electronic control systems like the magnetic setups in high-end vehicles. They work by monitoring the road surface mechanically and adjusting the damping to suit the conditions. This gives the Clarity a higher level of body control than the Mirai, while still offering refinement.

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In order to protect its highly pressurized hydrogen cargo, the Clarity's rear sub-frame — which houses the main hydrogen tank — has a series of plates and struts linking key joints of the frame to provide added support in case of a collision. The extra bracing adds weight, but the car has enough power to adequately propel the mid-size sedan's 4,167-pound mass. Its acceleration is typically electronic with a steady pull and tail-off in normal mode, and more sustained in sport mode. Thanks to its single speed direct drive transmission there is no break in acceleration. Honda also managed to seamlessly combine both mechanical and regenerative braking in the Clarity, with no noticeable step-change in brake effort at any speed.

Getting its fill

We took an almost-empty Clarity to one of California's 26 hydrogen stations, and you fill up in a similar way to a gasoline-powered car. Remove the cover from the filler valve and place the nozzle over the valve. Squeeze the handle to make a firm connection and the gas starts to flow.

Hydrogen fuel-cell technology has had a tough time in coming to market in the past. But Honda shows that an unconventionally powered, environmentally friendly car can be refined, practical, and maybe even a little fun (Honda is further expanding the Clarity line with coming EV and plug-in hybrid models). As its engineers make huge progress with power increases from hydrogen tech, you never know: maybe Honda's next fuel cell propelled machine will be a sports car. We could get behind that.

2017 Honda Clarity Fuel Cell Specifications ON SALE Now PRICE $58,490 (base) MOTOR Permanent-magnet synchronous AC/174 hp @ 4,501-9,028 rpm, 221 lb-ft @ 0-3,500 rpm TRANSMISSION 1-speed direct drive LAYOUT 4-door, 5-passenger, front-motor, FWD sedan EPA MILEAGE 68/66 mpge (city/hwy) L x W x H 193.5 x 73.8 x 58.3 in WHEELBASE 106.2 in WEIGHT 4,167 lb 0-60 MPH 8.4 sec (est) TOP SPEED 105 mph Show All