There was a time when Mazda had an obsession with Felix Wankel’s rotary engine. Decades ago, you could buy a sports car, sedan, wagon, or even pickup truck equipped with an engine that sounded like a thousand furious wasps. If you instead took the bus for your commutes, for a brief moment in time you could have boarded this, the Mazda Parkway Rotary 26, the first and what appears to be the only transit bus to get powered by a rotary engine. It’s also incredibly rare, with just 44 ever getting put on the road.
If you’ve been paying attention to recent entries of Mercedes’ Marketplace Madness, you might have noticed me mentioning a time decades ago when Mazda put a rotary in all kinds of cars. Indeed, Mazda says that in 1972, it sold about 100,000 vehicles powered by a rotary engine in America. Mazda’s rotaries were so popular that the company says that it finished out the rest of the 1970s with about half of its car production powered by rotary engines.
Mazda wasn’t afraid to experiment with the kinds of vehicles that got rotary power. In 1967, Mazda kicked off its revolution with its first rotary and its first sports car, the Cosmo Sport. From there, Mazda’s interest in rotaries only grew and eventually, buyers had a choice of vehicles like the North America-only Mazda Rotary Pickup, the Mazda Luce R130 Coupe, the Eunos Cosmo, and the RX-4 coupe, sedan, and wagon. Of course, who can forget legends like the RX-7 and its RX-8 sequel? On Monday at 4:20 AM, Mazda’s PR arm in the UK reminded us of another weird rotary creation: The Mazda Parkway Rotary 26.
Mazda Monday Fact: Just 44 examples of the rotary powered Parkway bus were produced between 1974 and 1976. Making this unique coach the rarest of rotary powered producton vehicles. pic.twitter.com/Rdg1IbCLsE
— Mazda UK PR (@mazdaukpr) February 27, 2023
How Mazda Fell In Love With Rotary Engines
To understand how Mazda got here, it’s best to take a look at what Japan’s automotive industry looked like during the time. As I mentioned in my piece about that six-wheeled tracked Honda Acty, in 1955, Japan’s Ministry of International Trade and Industry (MITI) got people on wheels in post-World War II Japan by coming up with the concept of a people’s car. Then, in 1961 MITI saw that a handful of Japanese industries weren’t quite competitive globally. The automotive sector was one of them and MITI developed a plan to spur growth, but it came with challenges for the automakers we now see as household names today. You read how it impacted Honda, here’s how it hit Toyo Kogyo, what Mazda was called back then:
In the 1950s and 1960s, Japan’s Ministry of International Trade and Industry, the architect of the country’s post-war industrial policy, was trying to make its nascent automotive sector globally competitive. It wanted to streamline the number of carmakers, reasoning that bigger manufacturers would be more likely to compete with US and European heavyweights. Smaller automotive manufacturers such as Mazda were vulnerable to a forced merger.
As Honda elaborated in its explanation, MITI’s plan also controlled market entry, so if a company wasn’t producing cars but wanted to, the plan might have locked it out. Mazda felt that an automaker that did things differently had a better chance at remaining independent. President of Mazda at the time, Tsuneji Matsuda, decided that Mazda’s path to survival would be to develop and sell a unique technology. That technology would be a different kind of engine.
That same year in 1961, Mazda sent engineers to NSU Motorenwerke AG, a company in West Germany that had been experimenting with Wankel-patent rotary engines since the mid-1950s. German engineer Felix Wankel began experimentation on his rotary back in 1924, earning a patent in 1929. While working with NSU, Mazda’s engineers discovered a problem with the rotary engines:
The Wankel rotary engine is characterized by the unique triangular shape of its rotor. As the rotor turns at high speed, the apex seal, which is attached to each apex of the triangle to ensure air tightness, undergoes friction with the inside surface of the cocoon-shaped rotor housing. This process causes abnormal wear on the chrome plating finish within hours, leaving traces called “chatter marks,” which are also known as the Devil’s nail marks. Finding a way to avoid such damage was critical to the development of a practical rotary engine.
Mazda formed a rotary research and development team consisting of 47 engineers. This team had a lot riding on their shoulders as the solution to the chatter marks seemed impossible. The engineers tried making apex seals out of horse bones and cow bones, but neither worked. Mazda says that as the project continued, many wondered if Mazda would be successful in making a practical rotary engine. Even within Mazda, company brass began seeing the rotary project as a waste of resources.
After two years of development, it was one engineer’s idea that finally forged a path forward:
At long last, the team achieved a breakthrough in 1963, when an engineer proposed the idea of changing the apex seal’s frequency characteristics by modifying its shape. A cross-hollow seal with a cross-shaped hole near the apex of the seal was developed and tested. The test proved successful, with no chatter marks appearing on the inside surface of the engine.
Mazda’s graphitealuminum alloy seal fixed the chatter mark problem and came with side benefits such as lower oil consumption and increased torque from the engine. Thus, Mazda’s rotary revolution took off.
Mazda Gets Into Buses
While Mazda was at work developing its rotary engine, the company was also getting into building buses. In 1960, it took a D1500 cabover truck and outfitted it to carry 13 people for the Japan Defence Agency. The seats also folded down, which allowed for the transportation of injured soldiers. The Mil-spec buses were used in Japan, but also shipped to the Middle East as an ambulance with two heaters and electric opening doors.
Mazda’s first transit bus would come in 1965 with the Light Bus Type-A. This 25-seat bus featured what Mazda calls “dream car” styling. Buses of the day were often blocky, but Mazda’s bus was rounded and featured a massive greenhouse with a rounded laminated windshield.
The company said that it was a hit at the 1964 Tokyo Motor Show. That bus came with a 2.0-liter engine that made a whopping 81 HP; definitely not a bus for getting places quickly. There was also the Light Bus Type-C, which followed the same formula as the Type-A, but came with a more conventional nose with flat glass.
Eventually, Mazda saw growing demand for a small, but upscale bus. On April 17, 1972 it unveiled the Parkway 26. This bus was far more advanced than its predecessors.
It rode on Mazda’s Titan commercial truck chassis and featured a number of engine choices. As David Tracy described about six years ago, a Parkway 26 (the number indicated seating capacity) could be optioned with a 2.0-liter four making 91 horsepower, a 2.5-liter diesel four offering up 76 horsepower, and a 2.7-liter diesel four pumping out 80 horses.
Again, the Parkway wasn’t a fast bus. Instead, it was meant to be luxurious. Mazda says that it was styled like a passenger car and inside, passenger comfort was a priority. It was built for the safety of the passengers and offered luxuries like a radio, a strong heater for cold winters, a soft ceiling, curtains, and other changes to make the bus more comfortable.
The bus was sold as the Parkway 26 Deluxe, which seated 26, and the Parkway 13 Super Deluxe, which maintained the same 129-inch wheelbase, but seating for just 13, making for even more luxury.
A Rotary Finds Its Way Into The Parkway
The bus got really weird in 1974 when, according to Mazda UK’s PR arm, the company decided to reduce the Parkway’s emissions. It would do that by taking a 13B rotary from the RX-3 and placing it in the bus under the floor between the driver seat and front passenger seat where the piston engines used to reside. In the new 1974 Mazda Parkway Rotary 26, the engine made just under 135 horses. The bus weighed about 6,250 pounds before the rotary came along. The engine reportedly brought along a pair of 18.5-gallon fuel tanks as well as a 1.0-liter piston engine to power the unit’s air-conditioner. When all was said and done, the weight ballooned an additional 881-pounds.
Like the other engines, this wasn’t about speed. Really, no transit bus is about launching off of the line quickly. Instead, the addition of the rotary was supposed to be for emissions purposes and to further heighten the luxury experience of riding in the coach. From Mazda:
This bus had the exceptional performance and quietness of a rotary vehicle, as well as outstanding environmental efficiency for its day, which cleared Japan’s exhaust gas emissions standards at the time by a wide margin.
And while it wasn’t a fast bus, it was geared for speeds better than many American transit buses and school buses. Some American buses go as slow as 45 mph. Mazda’s Parkway Rotary 26 was able to exceed 70 mph. Still, Mazda’s rotary bus experiment didn’t last that long. After three years on the market, Mazda sold just 44 of them.
So far as I can tell, this bus has the distinction of being the first and the last production bus to be powered by a rotary engine. And given its rarity, it’s also one of the rarest Mazda rotaries that you can find. It’s believed that just four survive in Japan, with one in a museum.
In 1977, Mazda ended its rotary bus experiment and the Parkway once again found itself powered by a diesel engine. The bus would get a second generation in 1982, which sold until 1997. Today, you’re not going to board a Mazda bus or a drive a Mazda rotary wagon. Heck, you can’t even buy a new RX car. Yet the company hasn’t given up on Wankel power yet. Mazda has revived the rotary as a range extender, which is exciting to see.
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It saddens me a little that they chose to make it quiet.
I wonder which i’d like more- a loud rotary bus or a 6V71 powered transit bus? It’s hard to beat the musical bellow of the detroit 2 stroke!
I’d rather have the rotary. I’ve ridden on many 6V71 buses. They range from gutless and noisy to rough, gutless and noisy when in a “T drive” setup used on old Flyer buses.
I’m pretty sure I’ve been in a Parkway 26 (non-rotary) when I lived in Saudi Arabia in the early 80’s. I have a vague childhood memory of the engine being under the floor a strange thing to me.
Wow, the Parkway 26, that takes me back. My parents owned a pub in northern New South Wales and had a 1970’s Parkway 26 as the pub’s “courtesy bus”. It was used to take pissheads… sorry, I mean, regular patrons, out to social events. Once it was used to take every member of my second grade class to my birthday party. Most popular I ever was I’d say.
It definitely wasn’t a rotary, if I head to guess going buy Australian conventions, it would have been a diesel.
This was the early 90’s and the bus was showing its age. It was not a luxurious vehicle, it looked nothing like the photos above. No velour, no curtains, no AC, if there was a radio it was broken. It had vinyl seats which included fold down “dicky seats” in the aisle that I thought were great fun to ride in. It was known by the regular patrons as “the rattler”. Good times, thanks for reminding me Mercedes!
When I look at that bus, I hear Os Mutantes’ ‘Minha Menina’ Let the psych-rock party begin.
Great article. Love that bus and I learned a lot. Thanks for not mailing it in with AI like your teammate Jason.
Coaster buses like these would be way more cool to import than kei vans that are all the rage. The LHD ones at least. They were all over the Middle East last I saw some decades ago, not sure if that’s still the case.
I want it, I want it, I want it, I want it … (You can’t have it!)
H/T The Who
It’s too bad they never sold these in the states. A world where the town’s Rotary club can have a rotary bus is a world to strive for.
“What engine’s in the Rotary bus?”
“It’s a rotary bus engine”
“I know it’s a Rotary bus, I’m asking what kind of engine it has!” (And so on and so forth.)
I guess the Rotary bus couldn’t compete with the Sentient Cat Busses that were common in the Postwar Japanese countryside.
Hey, 40HP/Liter wasn’t that bad in 1964..
Good thing rotaries are so torquey.
What on earth would make engineers think of using bone for seals ? I know leather was used for oil seals but this wasn’t the 1920s
throw everything at the problem
Bone and antlers can have a very low coefficient of friction and good wear characteristics, and are tough.
Very difficult combo of properties to get out of a material, especially in the 60’s.
Yes in cars but was used in boats prior to then.
It’s a cool bus, no doubt. I’d like to see what the Parkway 13 Super Deluxe looks like inside. What kind of luxury does the fewer seats give you?
Stripper poles for those Japanese salarymen junkets.
Despite rotaries having a bit of a “dirty” reputation now, back in the late 60’s and early 70’s they were actually widely considered by Mercedes, GM, and plenty of other auto manufacturers because they could have fewer exhaust emissions. This was for two reasons:
1) While their un-treated exhaust typically had high levels of hydrocarbons from all the thin crevices near seals and sections around the rotor near TDC, the exhaust was very hot compared to piston engines (less expansion, slower/later burn) which meant it was easier to clean up with a simple oxidation catalyst
2) For many of the same reasons, their nitrous oxide (NO & NO2, combined NOx) emissions were lower. Greater surface area/unit volume meant more heat transfer for a given amount of fuel & air, as did the slower combustion that had to spread outward further through a thinner-section rotor near TDC. Both of these combined to substantially reduce the peak gas temperatures, which in turn meant that very little NOx was formed for a given power output. This was perhaps more important than the hot exhaust temperatures because at the time it was MUCH harder to treat the exhaust to remove NOx than unburned hydrocarbons. The three-way catalysts that we take for granted today that clean up both NOx and HCs were just being developed and were quite expensive, unreliable, and restrictive to the exhaust, further hurting power and efficiency and thus any engine that didn’t need one would have an inherent advantage (also why Honda pursued the CVCC engine without a catalyst, among others).
The slower burn duration definitely hurts efficiency and necessitated 2 (all production rotaries) or even 3 (LeMans winning 26B 4-rotor) plugs per rotor, but it reduced NOx substantially, increased exhaust gas temperature, and allowed Mazda to avoid needing a catalyst for a while anyway. CO2 was not a regulated emission at the time, so the extra fuel consumption wasn’t a big deal in that regard (at least until the fuel crises of the 70s). Plus, most piston engines weren’t all that efficient at the time either, and got worse with the additional backpressure of a catalyst, the crank-driven air pump required by that catalyst etc.
Additionally, the rotary’s high power density (especially given the 1.2-1.3L marketing displacement) meant that it still satisfied customer’s power requirements despite the inefficiency, so for a brief window in the late 60’s and early 70’s it seemed like a magic bullet to auto manufacturers around the world.
Also, (at least early on) they could pass emission requirements without needing an expensive catalytic converter (for the reasons you state), unlike their piston counterparts, making them cheaper. Wankels also didn’t need to run on leaded gas.
Apparently, John Deere also looked at a rotary engine for tractors.
Very interesting.Thanks for commenting
I’ve never owned a rotary but I love them, I think they’re neat just in the fact they exist. For a small sports car they’re interesting and enthusiast enough. But why, just why, would you put one in a bus?
Check this out
John Deere experimented with rotary engines in tractors…
The D1500 bus looks like bizarro world Ford Transit. Also the separate engine to run the air conditioner in the rotary Parkway is only slightly crazy when you consider the size of som bus AC units. The Car Wizard bus has a V4 compressor the size of a Saab 96 engine.
Things that make you go hmmm …