>>I stand corrected, I just had a brain fart. But what about reducing MP, do
the
BMP, adjust the mixture to 50 LOP, then increase MP back to full ? I'd
expect
some adjustment to the mixture to be needed, and that could be done with a
table
like that:
2500 RPM, 38 MP => x FF for 50 LOP
2500 RPM, 39 MP => y FF for 50 LOP
2500 RPM, 40 MP => z FF for 50 LOP
2700 RPM, 38 MP => x1 FF for 50 LOP
2700 RPM, 39 MP => y1 FF for 50 LOP
2700 RPM, 40 MP => z1 FF for 50 LOP

Would that be ok ?

Marcelo<<

Well... it is a bit hard to do a cookbook on this.  There are other issues.

In those MP ranges (33" to 40" MP)  the  mass airflow vs MP relationship
loses its linearity that is otherwise pretty good down in the 25"MP to 32"MP
range.

I could map it out on the test stand.  But then it would change on hot days
verses cold days.  Less fuel flow on hot days.

In my view, with your current ignition system, you are better off to take
the fuel flow hit and enjoy the 7% gain in horsepower for the enhanced rate
of climb and get the climb over with quicker... and then get back to cruise
while LOP at about 250 to 265 Hp.  

And,  50F  LOP is NOT far enough lean of peak at 265 HP.  It really needs to
be more like 75F LOP at HP settings that high, in order to keep the
combustion event slowed down properly to control peak cylinder pressures.

I operate my TN IO-550 (300HP) engine at 265HP on a routine basis at cruise
for the last 1000 hours or so.  But I do it at 70 to 100F  LOP - - no CHT
above 380F.

When I need to climb more than about 3000',  I will usually go back rich of
peak and do the climb that way.  

One day we may all have  FTLR engines.  Until then.... the above is probably
a better way.

Regards,  George