So yesterday I went ahead and mapped my propellor rpm, and fuel mixture, to a couple of available axis I had on my Cougar throttle.I think I pretty much get the prop rpm, but on the fuel mixture I am curious:Do you just leave it set on auto in the config settings, or do it manually?If done manually, how and when is ideal for adjusting fuel mixture?Thanks for any tips,

If you go higher you hear and see the motor loosing rpm.Adjust mixture to have the motor on highest rpm. Have an eye on the fuel flow although. You can use this also to save fuel.

Usually I do not lean mixture below 5k ft in C172. Some guys do it above 3k ft, so its not clear boundary at all.However, when you are in cruise you start to pull mixture lever and watch EGT indicator. Needle (and EGT) will start to rise. At moment needle hold and go at other side (EGT lowering), stop to pull the mixture lever and push it milimeter or so to rise EGT a little for safety reasons. Done. :)Just do not forget to push your mixture level to the max when you are descending for landing.

Edited March 5, 201214 yr by g_precentralis

I have to say I haven't checked it out yet in MS Flight, but in FSX I set the mixture rich of peak: when you get higher, you have to pull the mixture back because the air gets thinner and there is a specific amount of air that has to be mixed with the fuel: the higher you get, the less fuel you'll need. Normally you pull back the mixture while watching the EGT: you will see the temperature rise and at a certain moment it will drop again: when you then push the mixture back until you are at the hottest temp, you have found the so called peak. Most people OR push the mixture even a bit further, after which you will be rich or peak and some people pull the mixture back again after they are lean of peak. It's not adviced to keep on flying at peak.However, in practice (in FSX) I usually often simply listen to the engine... When you start pulling back the mixture lever, you will hear the engine run louder. When it is at its loudest possible, you are at peak. Push the mixture forward again to go to rich of peak (the sound will be a bit lower) or pull the mixture a bit further back to get lean of peak (the sound will also be a bit lower).You have to check your mixture during climb and descent because the best mixture is different on every possible altitude. You might also wait with setting the mixture until you are cruising (if you aren't cruising high).

Very helpful, thanks guys.Yes I have been playing around with the mixture in Flight and do notice that difference in the engine sound.

The usual real world advice I've read is that during cruise, you lean the mixture until the engine runs rough, then enrich it until it's running smoothly then enrich it just a bit more. During a climb, you generally want to keep the fuel flow maxed. In FSX, the peak power comes about 3/4 of the way between peak exhaust gas temperature and peak fuel flow (if you've got the instruments to measure both of those), but most advice is that if the engine is having to strain a bit during a climb, you want a richer mixture.If you have an EGT gauge, it's easy to tweak the engine settings for cruise. Run peak EGT but not over 1350 degrees F, 730 degrees C.I don't know about anyone else, but I'll lean the mixture in Flight during cruise even if I'm below 3000 feet. It makes a difference if you're trying to fly the whole coastline of the big island... full rich in the Stearman at 500 feet and you run out of fuel. Lean, you land with 20% fuel left.Hook

During a climb, you generally want to keep the fuel flow maxed.

Not necessarily true... At least in the C172's that I have flown for real, if you are climbing past 4000 feet and don't start leaning out the mixture, your engine will eventually start running rough the higher you climb. Remember that the air density decreases with gain in altitude and the mixture should be adjusted to compensate. If you know you are going to be climbing for awhile, it's a good idea to periodically adjust your mixture. It's technically part of both the "climb" and "cruise" checklists. Also, if you don't lean your engine properly (and there is more than 1 accepted way of doing this, something that pilots have argued about for years), you can increase your fuel burn and decrease your range. Also, flying too rich for a long time can increase the risk of lead build up in the engine and can increase the chances of spark plug fouling. You don't want that! Of course that doesn't matter in a simulator so much -- but I like to try to keep things as real as I can. ;)

Edited March 5, 201214 yr by Xpendable

Real world:My airport sit's at 4607' msl. Engine start with full rich, then immediately lean. If I don't lean, you can tell when taxing. You'll also find some plug fouling when doing the mag checks. At my altitudes, the mixture knob never goes back to full rich the entire flight, including landing. It's recommended to start thinking more about leaning procedures at around 3000', because density altitudes can be higher.FSX starts to get critical around 6000' msl. I just use engine sounds for FSX. For my plane, I used the EGT, as I became use to where the best settings are. EGT can vary, due to where the sensors are placed on the exhaust pipe. I wouldn't be that critical for a sim, and just use best power settings. I've also noticed, that on quite a few sim planes, the engine will sputter or die when the knob or lever is pulled back (lean) to real life settings.

Oh yeah, one more thing to keep in mind also... Outside air temperature as well as how rapidly the temperature decreases with altitude (called "lapse rate")c an have a big impact. 30F degrees at 4000 feet is much denser air than 70F degrees at 4000 feet. The "standard lapse rate" is considered to be a drop of 2 degrees Celsius with each 1000' gain in altitude. If the temperature drops faster than 2 degrees per 1000 foot, then you have air that is considered denser and more stable. (We see this in the midwest with winter flying and the air is usually very smooth). On a hot, humid day, the temperature decrease with altitude might be less than 2 degrees C with each 1000' gain. This results in less stable air -- more prone to turbulence and other kinds of fun weather.

During a climb, you generally want to keep the fuel flow maxed.

Not necessarily true... At least in the C172's that I have flown for real, if you are climbing past 4000 feet and don't start leaning out the mixture, your engine will eventually start running rough the higher you climb.

I didn't mean you keep the mixture maxed. As you climb, fuel flow max will be achieved at a leaner setting.Hook