75 deg Rich of Peak

My previous post on Mixture Authority changed emphasis during the thread to Leaning on the Ground… I certainly learned much from this discussion also. Thanks… However, the problem that I continue to have is the inability to achieve 75 deg ROP in cruise. In fact, sometimes my engine will only run at peak EGT with the mixture control full forward. Turning the aux fuel pump on will only yield a 50 deg ROP indication. Some answers to the thread indicated that they had not experienced this problem with their airplane. Still looking for someone who has had this problem and the cure. I have had the airplane at two service centers and recently at the factory. Thanks to those who responded previously who did not see this problem…

I did have a similar problem happen on our SR20. There was too much play in the mixture and I could not get it rich of peak. We pulled the cowling and the swage (sp?) on the mixture cable was loose. Replaced the cable under warrantee and the problem was fixed. I have no idea if you have the same problem but it may be worth looking at.

I do not want to repeat too much of was has been said, but the SR20 has an AUTOMATIC altitude correction for the mixture. So the plane is already leaned ROP when you pull the mixture lever back. There are cases where the leaning is so perfect that you cannot get much higher temperatures - maybe only 25 or 50 F EGT. This is perfectly okay. Push the lever back to full forward - the altitude correction remains on. I use the leaning only when really high, say above 7000 ft with high OAT - there the altitude compensation alone is not enough.

If you want to go LOP, however, you must use the red knob, for sure.


Timm Preusser CFII N747TG