Hey guys,

Just how much does and engine lean when up in the air? When setting engine up I lean to highest RPM on high throttle, then richen a little. But am now unsure how much to richen up. Have just read an article and some people suggest a couple of clicks, and others are suggesting a quarter of a turn. Quite a difference!

Any advice?

Thanks,
Paul

There is no general answer. How much to richen is engine/prop/airplane/application-specific. People say 3-500 RPM rich from peak RPM. Probably the answer is somewhere in that range for your situation. I would err on the side of a little richer than rather than too lean. The proof is in the flying.

It would help to know the engine and prop you are working with.

But on a typical 46 turning a 11x6 I would drop the RPM by 200 to 300 then do a prolonged nose up and make sure that the engine did not sag.

Yeah, I am running an Irvine .46 swinging APC 11 x 6

Cheers for help

The size of your tank and the engines abillity to draw fuel will determine how much the mixture will change throughout the flight. Peak out the needle pointing straight up with an empty tank, this is as lean as it should ever be. When the tank is full and the plane lever it will be a lot richer. If the difference is too much then use a smaller tank or smaller prop or smaller carb.

Ok guys, so reduction by a few hundred RPM should be fine? Am thinking of getting a tachometer until I get used to the difference...

Paul

I don't have any set figure for how rich to tune on the ground because I like to sneak up on a decent setting during a few flights and see how the engine reacts to changing fuel levels and attitude. First flight will be set so it's just barely out of a 4 stroke and if it doesn't want to take off then the engine is too small for the model . If it stays noticeably rich for a whole flight doing some manoeuvres like large loops then I know I've got a safety margin to lean it out a little.

With my Rossi 45, it flies around level in a 4 stroke but as soon as I bring the nose up it goes into a very strong 2 stroke which gives some idea of how much they can lean out. If I did the usual of richening a couple of hundred on the ground it'd be way too lean doing loops etc. The ultimate test is when the tank is nearly empty and doing the longest climb as near vertical as possible.

Look at it this way:

If it's too lean--you'll deadstick and possibly ruin the motor.

If it's just a bit too rich for maximum power, but stil pulling good and flying the plane like you want-- then 2 things wil occur
1-it won't die
2-you won't ruin it

I see guys tweaking the high speed needle for everything it can give and then they wonder why their engine dies. Hmmmmmmmmm [sm=spinnyeyes.gif]

And I see guys tuning so rich that it won't spool up and drag the airplane off the runway.

Find a happy medium and err to rich. Your engine will last longer and you will avoid a deadstick--in which case--the airframe may last longer too. Depends on how good you are at deadstick landings.

After you fly for a while, you'llpick up on the sound real easy. If you richen it up, take a few laps and if its rich it'll sound sloppy vs the nice high pitch whine, Then leand real quick and andjust a couple clicks and try it again. Sometimes that is a better way to do it because the setting can change a tad after the engine warms up.

Everybod is always in toomuch of a hurry to get in the air when they show up and this can overlook problems. I get to the field, run it up and dial it in , then shut it down, refuel, and check it again. Whats an extra 5 minutes to get it right the first time and have a fun morning.

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Kweasel has nailed it. This is the only sure-fire way of determing your setting. You will be amazed at how rich your engine will run after you fill the tank and restart the engine. Resist the temptation to lean the mixture further. Learn to live with the early flight richness and deadsticks will mostly cease. Not only that, but your engines will last a LOT longer.


Ed Cregger