Ground Leaning of aircraft

[CO_Skymaster]

I performed a search on leaning and didn't find a good answer, so I'll ask here.

When I was learning to fly, I was thought during run up to lean the aircraft until maximum RPM was reached and as soon as the RPM started to drop off, you enriched the mixture about 1 inch. When I finally started to use an EGT, it was lean to max temperature, then enriched about 50-100 degree. I still use similar method before my mag check, which works out pretty well.

I have tested this method and during take off, fuel flow end up being about 11 gph. However, from the plaque in my aircraft, it list take off at 6000 feet should be about 14 gph. I normally push the mixture levers to equal the 14 during take off roll, just incase.

Has anyone else run into this discrepancy, do you leave the mixture at the setting determined by ground leaning?

[skymstr02]

On take-off, the engines don't have the cooling airflow over the cylinders due to the attitude of the airplane, so the engines are relying on the additional cooling provided by the enriched fuel mixture. Without the enriched mixture, you could have hot spots on the engine that are not measured by the instruments installed.
One of the shortcomings of an aircooled engine is the reliance on additional fuel flow to ensure adequate cooling.
Your leaning techniques are fine for cruise flight where there is enough airflow over the engine.

[CO_Skymaster]

Thanks for the answer. I guess it is safe to err on the side of caution and use 14 gph.

Karl