Dear subscribers,

A while back I reported a warmer cylinder 4 during climb at 32 MAP and 2500 rpm. Lynn recommended I could test high boost during climb and see if it makes a difference.

In the mean time I cranked up my fuel pump by approx. 1 GPH. At take-off I see now 42.5 GPH at 38.4 MAP 2680 rpm (on a TSIO550 B which is rated for 38 MAP at 41…43GPH according to my manual).

In climb under full rpm/MAP engine stays very nice and cool.

Climb 2500 rpm with 32MAP: all EGTs show the same, after increasing the fuel flow all CHTs stay generally a bit cooler but CHT 4 is still the one that runs a little warmer. During climb when CHT4 approached 380 I turned the high boost on – the CHT went down by approx. 10 degrees back into the 360’s. During the climb to 18000 I had the boost pump on 3 times for may be 2 min each time. The Fuel flow increased from 30.5 to 33 GPH. I climbed with +-170 kts at 1000 fpm.  This is new: usually I was never able to get the CHT down in climb unless I decreased the climb rate.

Question: is it a reasonable practice to use the high boost for engine cooling? How long can it run in high boost without getting damaged?

Craig reported earlier that he had his fuel pump modified to feed more fuel under partial power – this sounds complicated and expensive and if I don’t have to I would rather not go there.

Thanks for you input

Ralf