1. One like the Mazda 13b only has 3 major moving parts. The eccentric shaft and two rotors.

2. It was easy to rebuild.

3. It was about the size of a 5 gallon bucket so it would fit in almost any car.

Downsides -

1. Fuel consumption and emissions. Even when Mazda tried turbos and fuel injection it wasn't enough to get good gas mileage out of the engines.

2. It didn't have much torque.

3. You couldn't overheat the engine. Once you did that the rotor seals swelled up and once they cooled off the seal was broken and the engine would burn oil.

4. You couldn't use the wrong spark plugs like many people tried to do to save a few dollars. That would often break off the apex seals and you would lose compression.

In the 1980s I had some friends that drag raced them in small Japanese cars and I helped now and then on the rebuilds. I have always been impressed with those little engines.
My mother also bought a brand new RX3 wagon when I was a kid around 1973.

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