“… a considerable percentage of the fuel leaving the chamber unburned.”
I bought a used ‘79 RX-7 in 1990 with about 130,000 miles on it. When it started up, it emitted a large cloud of white vapor.
When I turned it off, usually at the gas station, that un burned fuel ignited in the exhaust line. It was not unlike a gunshot.
I’d like to apologize to those whose hearts I stopped.