Lynn,

Thank you for this great advise – a fairly simple solution for an annoying problem.

I will turn up my fuel flow some more (above to what my book says 41…43) to get the 44 GPH which was recommended several times here.

Ralf

Ralf,

According to what I have been told, by some folks at  Continental, you do not need to worry about harming the electric fuel by using it as needed. You could have left the high boost pump on from the time the CHT started the increase above the others until you reached your cruise altitude. So, yes it is reasonable to use your high boost pump for cooling. Your engine will not flood and it will be happy that you are keeping it cool!

I told you I have used the high boost pump more than once to keep the CHT from getting higher than I wanted. If I need it I use it.

You might want to increase the engine driven fuel pump output just a little more, to 44 GPH.

Since you said the CHTs stay in the area you like when you keep the RMP at “full” (2700?) you might want to do the entire climb at 2700. Again, according to the folks I talked to at Continental operating at 2700 RPM during the entire climb will not hurt your engine.

As the people at GAMI say, “it is not how HARD you run your engine, it is how you run your engine HARD”. Just keeping the CHTs cool is going to go a long way toward making you and the engine happy. Using the high boost pump and/or operating at 2700 RPM, as needed, will do that.

So, be not of faint heart.

Lynn

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