fuel/air mixture

There is no real single answer. It is a range and not an exact number. Each aircraft / engine is different. Outside air temps (cold vs hot) affect it, air intakes (air filters and air boxes or filter directly on carb), cowlings, open air engines, prop pitch / rpm, ect... Cruise rpm plays a big part and that's different with many owners. I see them anywhere from 1200 - 1450 with the average in the 1300's again depending on rpm..

Just stay within the proper EGT range and leave it alone.

Thank you for everyones comments!  My EGT's run withing 20 degrees when the cowl is on or off.  I have not had this engine long enough to know if outside temps change the EGT much but so far I have noticed very little difference when it is warm or cool.  I need to watch this closer to see what affect outside temps have on EGT's.   However, I know there is a direct correlation between mixture and EGT's.  I know this as I have seen the affect needle height and the idle adjustment screw has on EGT's.  Turning the idle mixture screw in 1/2 turn will make the EGT increase around 200 degrees.  The only reason I was messing with the idle adjustment screw is because my 912, like others, has the needle set at a different height on each side.  I noticed that my EGT's were even when running above 3K RPM but they were uneven when in the idle circuit below 3K RPM.  I was able to get my EGT's on right/left side exactly even by adjusting my idle adjustment screw.   I know the manual specifies to set the idle adjustment screw at 1.5 turns but my EGT's are not even when I do that.   I have watched the you-tube video suggested on fine tuning a 912 and am thinking I may install an O2 sensor since it is fairly cheap and will give me peace of mind that my carbs are set up right. 

I wouldn't try to get the EGT's high and or lean the engine out. There needs to be a reliability factor in there so you don't seize the engine. Plus you may not like where you have to land. You want the engine to last to TBO. Trying to lean it out would be playing with fire. The engine would detonate before you even knew it and then thousands of dollars to repair it. Rotax built in safe limits for a reason. I'd live with them and enjoy your flying. With tens of thousands of engines out there and millions of run hours plus their testing they know what they're doing and why they did it a certain way.

I agree with you but why does rotax say 1470 is normal then. That could make the range more like 1300 to 1550 . We can also control the range with mixture>

I also was told Egt is more an internal temperature of the burning gas, not really affected by air temps once the engine is up to temp?

You can see how we are all confused. Can we ask someone from rotax to define the correct EGT range for engine life, efficiency and engine safety. Seems like they put it in the manual for a reason. If1300 is normal why not change correct the manual? I would like to know why they chose 1470 is all.

Thank you for sharing your knowledge as we don't have any rotox shops close by me

Firstly 1470 actually 1472 is 800 degrees C.....A nice round number.

There is nothing wrong with 800 degrees .....so long as that is it.

The problem is that IF you go too high you have problems, detonation melting pistons etc.

Carbs are not so good at maintaining a narrow range of temps over a wide variety of conditions, basically different Relative air densities and loads, and OAT's and Fuel compositions.

By stating a range that is acceptable then hopefully most people will be satisfied and not chase an ideal that is unattainable and varies anyway day to day.

Rotax will have done thousands of hours of Dyno testing and in effect are saying that if you keep to this range , not only is the engine safe but that the power difference is minimal.

With the EFI engines that have more closed loop feedback info the ECU can run the engine leaner and cleaner while still being safe within the other variables.

Perhaps this is why the IS engines produce a couple of Hp more than the carbed engines.

Practically we do not notice whether the engine produces 100 or 95 hp and as soon as we go UP a 100 hp very quickly becomes 95 or 90 pretty quickly

Rotax has been doing this engine stuff for 102 years they know what they are doing...

Keep within the range and enjoy the flying...