Turbos and intercoolers / part II

Follow-up to Kevin:

<<We are taught the best economy is at peak, and best power is at 50 ROP. To me this implies that the max HP is specifically at the 50 ROP point.
>>

Well, *WE* (you and I both) were taught incompletely. As it turns out, best power occurs at approximately 80dF ROP. The highest possible CHTs and internal peak cylinder pressures occur at 40dF ROP. In my book, that makes 40-50dF ROP the WORST place to run my engine at any power setting above about 65%. Highest heat and pressure per given HP. Baaad medicine and not at all compatible with engine durability. As for best economy, it occurs at the BSFC min point... approximately 40dF LOP. (I've got those charts from TCM and Lycoming, too!) BSFC = Brake Specific Fuel Comsumption. In TCM and Lycoming engines the BSFC min is about .38 HP/Pound/Hr and occurs at about 40dF LOP.

Another point made earlier in this thread which needs correcting is that "as long as FF is adequate at METO, everything is OK." That is absolutley TRUE but, as it turns out, NONE of our TCM and Lycoming engines have been set up with adequate FF for Takeoff. If your unmetered FF is at the HIGH end of the factory range, it is still a gallon to 1.5 gph too low. TCM has begun to recognize this and has increased the unmetered FF on newer engines. In our view, they are moving in the right direction, but are still slighly low on the FF at takeoff. Again, we have the data to back up our position.

I have all the TCM, and Lycoming data to support these statements. As a matter of fact, these charts are in your POHs if you are familiar with reading them.

If you 337 folks would like, I'll be happy to come by one evening for a *chew-the-fat-engine-management-session* (complete with DATA) over a beer or two!

See ya next week.

Walter