Imagine! A world in which you can own a small, cheap, rear-wheel drive sports car that burns not the finite processed dinosaur juice extracted from the ground, but hydrogen in all its abundant glory! This isn't some science fiction dream — it's something Mazda actually did back in the early 1990s.
Yes, Mazda once built a Mazda MX-5 Miata that ran on the miraculous science-fuel known as hydrogen. And it did so with a rotary engine, of all things, making it one of the first in a long line of amazing rotary hydrogen cars that didn't really go anywhere.
And in combining those three things — hydrogen, Miatas, and rotary engines — this experimental vehicle from 1993 became perhaps the most Mazda-y Mazda ever made. It's as if Jeep constructed a Wrangler purely out of rocks, and freedom, and punching Hitler in the mouth.
Like Honda and Toyota, Mazda has dabbled with various forms of hydrogen power in a number of experimental cars over the years. In most cases, these Mazda hydrogen vehicles had rotary engines as their powerplants.
Track day, bros and backroad hoons everywhere love Mazda's rotary engines for their ability to achieve stratospheric revs with unbelievable smoothness. The problem is the rotary engine falls down in important areas like fuel economy, emissions and the durability of their apex seals, which is probably why it's been kept out of production since the RX-8 was put out to pasture a few years back.
The rotary engine has another unique quality: it's extremely well-suited to hydrogen power. Mazda explains that achieving ideal combustion with hydrogen as a fuel is extremely hard in normal piston engines because the fuel is extremely flammable and requires less energy to ignite than gasoline.
But on a rotary engine the intake chamber is separated from the combustion chamber, reducing the risk of abnormal combustion and making hydrogen more viable as a fuel source.
As you can see, these engines actually burned hydrogen in the internal combustion process; they were not electric fuel cell vehicles like the Honda FCX Clarity and others. The advantages are still there, like clean emissions and a fuel source we'll never run out of.
Mazda's first foray into hydrogen rotaries came in 1991 with the HR-X, unveiled at that year's Tokyo Motor Show. The decidedly Dolphin Mech-looking car could travel 125 miles on a tank of hydrogen without refueling its rotary engine, and it led Mazda down the path of testing other hydrogen rotary cars to examine their commercial potential.
Fast forward to 1993, when Mazda decided to put a hydrogen rotary into a car that doesn't look like a character from a manga your little sister reads (well, it still kind of does, but we love it anyway): the Miata, or Eunos Roadster as it was known in Japan at the time.
On the surface it looks like any old Miata: small, two seats, open top, delightful pop-up headlamps. But under the hood it was remarkably different from any Miata we've seen before or since. It dumped the Miata's 1.6-liter inline four for a two-rotor, 1.3-liter engine adapted from the one used in the RX-7. (It's not clear whether it had the turbos or not, but I don't think it did.)
Outfitted to run on hydrogen, this Miata put out 118 horsepower and 121 pound-feet of torque, which wasn't that far off the output of the standard NA Miata's four-cylinder engine.
Popular Science previewed the car back in October 1993, and they said the little Miata was also outfitted with a storage tank used to hold the hydrogen fuel in a safe state. Inside the tank was a form of hydrogen mixed with metal to create metal hydride, which was then heated to give up the gas fed to the engine.
The tank was a system of tubes stacked like logs in the Miata's trunk, and within each tube was a grid of cells for the metal hydride and tiny pipes for heating and cooling water. It's a complex and heavy setup for sure.
A year later, the other Popular, Popular Mechanics, actually got to drive the thing. That's where editor Jim Dunne encountered the biggest difference between the hydrogen Miata and its conventional counterpart — the 500 pound weight difference necessitated by the fuel tank.
This probably would have put the diminutive Miata around 2,700 pounds or so, making it easily one of the heaviest Miatas ever, if not the heaviest. Obviously, that cut into the car's performance.
For one thing, you instantly notice this Miata does not have the smart acceleration you expect from Mazda's small sports car. For another, this car's handling is slightly less nimble than the norm.
[...] But in reality, during my test drive with the most-rare Miata, I found that the car performs and handles on a level with some current midsize sedans. Acceleration is slower than you'd expect in a rotary-powered Miata, because of the 120 hp rating and hundreds of pounds of fuel in the trunk. And weaving through a small slalom course betrays the extra weight of the car, revealing a slower response to handling maneuvers.
A Miata that handles like a midsize sedan? You may as well have bought a Chrysler Sebring!
Weight and complexity weren't the hydrogen rotary Miata's only problems. The magazine reported that filling up the tank with enough hydrogen for it to travel 60 miles took about 10 minutes, and while that's not as bad as an electric charging time, it's still more than gasoline drivers were used to.
Mazda built the rotary hydrogen Miata purely as a test vehicle, to keep experimenting with the viability of hydrogen as an alternative fuel. At the time they were targeting hydrogen-fueled production cars by 2020. A few decades later, it seems to be a non-starter, unless we're talking about hydrogen fuel cell vehicles, and even those are still in the baby stages with plenty of critics saying they have no real future.
That hasn't stopped Mazda from trying. They built and experimented with rotary hydrogen vehicles for years after the Miata, starting with a Capella wagon tested in Japan for four years starting in 1995. The company also had a succession of RX-8 prototypes built to run on hydrogen or gasoline. (Road & Track called one of them "sluglike" back in 2010, which is not encouraging.)
And as they discontinued the RX-8 in 2012, they insisted they were continuing research into ways to make the rotary more efficient and earth-friendly. They've even talked about using a hydrogen rotary engine as a range-extender on an electric car, but nothing has come of that yet, production-wise.
So the hydrogen rotary engine isn't there yet. It wasn't in 1994 either, and it may never be. Still, it's a noble attempt, and it's fascinating that Mazda once chose their roadster as a test car for this technology. I'd like to think it's still out there, getting thrown through slaloms at some research facility in all its hydrogen-y, midsize sedan-like glory.
Enthusiasts have always wondered why Mazda never put a rotary engine into a Miata. It turns out they have, just not in a way anyone expected.