Simanaitis Says

On cars, old, new and future; science & technology; vintage airplanes, computer flight simulation of them; Sherlockiana; our English language; travel; and other stuff


MY FIRST hydrogen internal-combustion drive came in 1994 when Mazda invited me to Vancouver, B.C., to experience a special Miata. This one had an RX-7 rotary engine fueled by H2. We already owned our Miata by then (see, so this was a perfect opportunity for a mini-comparison.

Like any Miata, the hydrogen-powered example was good fun. However, its hydride tank occupied most of the trunk. The metal-alloy particles working its hydride magic added 500 lb. back there. And its refueling took around 10 minutes for only 60 miles. Recall (“H2 I.C., Part 1,” that hydride storage depends on the (slow) adsorption of H2 onto the surface of the metal-alloy particles.

The rotary engine produced only 120 hp on H2, just a tick more than a Miata’s stock 1.6-liter inline-4 of the time. Thus, it wasn’t a rotary rocket. Also, that added weight detracted from Miata nimbleness. It handled like quite the ordinary car.

Nevertheless, the hydrogen-powered Miata was an interesting concept. And, while in the Vancouver area, I had my first visit with fuel-cell specialists Ballard Power Systems in nearby Burnaby, B.C.

I’ve also driven a more recent H2 I.C. Mazda, this one a dual-fuel RX-8 in 2010 (see

The Mazda HRE visits Univ. of Calif. Irvine’s hydrogen station. This dual-fuel car can refuel at ordinary gasoline stations as well.

The Mazda HRE, as in Hydrogen Rotary Engine, was an interesting drive. This car’s compressed hydrogen storage eliminated the hydride tradeoffs. However, it still suffered from reduced power and range, both inherent in such dual-fuel applications.

A rotary engine’s revolving combustion chambers work fine with hydrogen. Dual-fuel capability, though, compromises the benefits of either fuel.

Hydrogen has an extremely high octane rating, effectively 130+. But if gasoline is the other of the dual fuels, the engine cannot exploit this octane through higher compression ratio. Plus, of course, dual-fuel range is compromised by requiring dual tanks.

I concluded that the Mazda RX-8 HRE could serve as a bridge, but it would be a lot more fun as a dedicated H2 car. ds

© Dennis Simanaitis,, 2012

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This entry was posted on October 9, 2012 by in Classic Bits, Driving it Tomorrow, Sci-Tech and tagged , , .
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