BMW Drops Gas For "Mono-Fuel" Hydrogen 7 Prototype
By John O'Dell March 31, 2008
By John O'Dell, Senior Editor
SACRAMENTO, Calif. --Those sly devils at BMW waited until today to drop the other shoe.
Turns out the Hydrogen 7 that cleaned up in a recent Argonne National Laboratory emissions test wasn't one of the bi-fuel, gasoline-or-hydrogen internal combusion models the automaker has been testing. It was a new mono-fuel model, built to run only on liquid hydrogen.
BMW officially debuted the car -- which looks just like the bi-fuel models -- at the National Hyrogen Association's annual conference here in California's capital city.
The big differences are that the bi-fuel models have gas tanks as well as hydrogen tanks, and engines that are tuned to run well on gasoline, meaning that performance and fuel economy drops when they are driven under the influence of hydrogen. By better optimizing the momo-fuel engine's turning for hydrogen, engineers boosted fuel economy to about 18 miles per gallon from 16 mpg, a company spokesman said. Range on an 8 kilogram (17.6 lbs.) tank of hydrogen has increased to 140 miles from 125 miles in the bi-fuel version.
Officially, horsepower, 260; acceleration, 0-62 miles an hour in 9.5 seconds; and top speed, 140 mph, all remain unchanged. But we're told unofficially that the re-tuned engine has a little more pep than its bi-fuel cousins.
It also has cleaner emissions. So clean that Argonne testers have labeled it one of the cleanest internal combustion engines ever produced, with "near-zero" bad stuff coming from the tailpipe.
No plans, yet, to produce the mono-fuel model, though. The bi-fuel adds 300 miles of range with its gas tank, for a total of 425 miles, and that suits 7-Series users far better than 140 miles. BMW has just two of the hydrogen-only 7s, versus more than 100 of the bi-fuel models.
The company's not done experimenting, though.
Next up is a supercharged version of the hydrogen engine, to replace the power lost by running on a fuel that has far less energy density by volume than does gasoline.
Supercharging is expected to boost the engine's power density from 44 horsepower per liter to somewhere in the range of 94-121 horsepower per liter, depending on how much compression is dialed in.
BMW says it will likely use a smaller engine than the 6.0-liter V12 in the present Hydrogen 7, however.
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