Mazda Once Built a Rotary-Powered Minibus - and Added a Second Engine Just for the AC

Most car enthusiasts know Mazda for the rotary engine in the RX-7, RX-8, and Cosmo. But in the early 1970s, the automaker had a wilder idea: stuff a Wankel into a minibus. 0-liter piston engine solely to run the air conditioning. Only about 44 were ever built.

The story starts with Mazda’s push into North America during the 1973 oil crisis. With gas prices soaring and shortages widespread, Mazda saw a chance to promote its smooth, quiet rotary engine as a fuel-efficient alternative for public transit. 3-liter twin-rotor 13B engine making just 135 horsepower and 132 pound-feet of torque.

That was fine for a sports car, but not for hauling 26 passengers. The engine struggled so badly that running the AC compressor was out of the question, so Mazda added a second engine just for that task. That fix added nearly 900 pounds, pushing the bus over 7,000 pounds total.

The extra weight made everything worse. The 13B had to rev hard just to move, which killed fuel economy, the very thing the bus was supposed to improve. Mazda tried twin fuel tanks totaling 37 gallons, but that only extended range without fixing the core problem: the rotary simply lacked the torque for heavy work.

The bus was painfully slow, and operators quickly gravitated toward conventional gasoline and diesel versions of the same chassis. By the mid-1970s, the rotary experiment was over. Today, the only known running example sits in a museum in Augsburg, Germany.

The Parkway Rotary 26 taught Mazda a hard lesson: rotaries belong in lightweight sports cars, not buses. That knowledge directly shaped the legendary RX-7, and Mazda still uses rotary tech today, as a range extender in the MX-30 e-SKYACTIV R-EV and in the Iconic SP concept. But the little minibus remains a fascinating footnote: a bold idea that physics, and a lack of torque, simply wouldn’t let succeed.