Lean of Peak operation
 

When operating LOP what is the normal ground speed reduction that you see? I see about 8-10 its at 60% power.

My fuel burn goes from 20 gph to about 16 gph typically at 7 - 9,000 ft. Cylinder head temps drop 25 - 40 degrees and the EGT stays the same, about 1380 degrees. I find that synching the engines is more sensitive during LOP and it doesn't seem to be quite as smooth running while operating LOP.

When I had my P337, it was pretty consistent at 23gph, about 50LOP, I would see 184KTAS in the high teens. My particular P337 had intercoolers, air conditioning, deice boots, VGs, and all of Bell's cooling mods though, so it was pretty draggy. It ran well LOP though, and never had any issues with CHTs.

If flying NA, optimal leaning to LOP from Best Power will gain you a 3 gph fuel savings (per engine) and cost you 3 knots. If you are losing more than 3-4 knots, the leaning is farther LOP than optimal. It's not hurting anything, but you are giving up performance.

If turbocharged, you can save fuel AND go faster than when ROP because the CHTs are better controlled.

How far LOP one should set the optimal mixture depends on the power being produced. It's a straight-line variation from about 15dF LOP at 60% power to about 90dF LOP at 90% power.

Jeff, what degrees lean of peak would you operate? Was that the set point for you or was the GPH?

Herb, 50LOP was where I ran the P Skymaster and it worked well. If I went leaner, the engines would start to miss, especially the rear one. If I went richer, I would get into temp issues (CHT and TIT) until I was quite a bit rich of peak, like 150ROP. If I had that plane now, I would try running it at 2450RPM, top of the green MP and 50 LOP. This might get me more speed. I was running at 60-65% power the way I was flying it. I took the APS course after I sold the P337, and would fly it a little different today. In my P210 I run 50LOP, but at higher power settings, so I really don't loose any speed, just go the same speed on 3gph less fuel. The TSIO 360 will run smoothly LOP if set up properly.