Critics of lean-of-peak engine operation claimed it would ruin engines. Two years and 600 turbo’d Cirri later, they’ve been proven utterly wrong.

By Paul Bertorelli

Start with a heaped serving of ignorance, add equal measures of industrial inertia and mediocre engineering, add a dash of petulant, not-invented-here intransigence and you’ll have a lucid understanding of how the airplane industry looked at the mundane world of engine management 10 years ago. Or, more accurately, how it looked at engine leaning.

Five years before that, General Aviation Modifications, Inc. had begun marketing its calibrated fuel injectors to wide market acceptance. Along with that, came the old-

The SR22’s TNIO-550, below, is placarded to run lean of peak by required max power fuel flows, above. Owners rave about economy and cool running temps.

new idea of running engines lean of peak EGTs to save fuel and tame high CHTs. Reaction from the entrenched interests was harsh. You’ll fry the cylinders, said Lycoming. You’ll fry the valves,…