Peter, can you post the CHT´s from the climb to 6.000ft?
The whole flight
The 1st rapid rise is the climb and the 2nd rapid rise is the go-around after the ILS. The GAMI test was done about 80% through but you can’t really see it in the above, in the CHTs.
because higher up there isn’t enough air for the engine at such low RPM
That is where the turbo comes to the fore.
As well as getting 150 knots, at LOP the engine is cooler and at 65% power one is being gentle to the engine which usually ensures it has a longer life too.
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thx Peter I was interessted how the spread changes between climb and cruise but it looks verry similar! It looks like 40-50F?
I have done that before – there is no measurable MPG increase. There is just the 2nd order effect
I have not managed to find that 2nd order benefit myself, but always looking to learn more!
First order benefit of running lean and green, lower CHT’s have been widely reported.
Try doing the MPG test at different RPM, like I did in that link I posted above.
Then, at the low RPM, try both peak EGT and LOP. I would expect to see a very small additional fuel saving by using LOP at low RPM.
Ah, yes! I am familiar with low RPM = less frictional loss theory.
In context of engine operation is that not a primary order effect?
Regarding engine operation, personally I don’t like to run at peak EGT with high MP and very low RPM.
The piston receives a good thump every second revolution, which is much higher at low RPM and very high MP.
I think it is an unessary stress on the crank and big end bearings, which is totally avoidable.
The solution is to close the throttle. However, that in turn is very hard on the ring seating during the induction cycle.
Further there is an efficiency reduction due to pumping losses, by having the big air pump work against the throttle plate.
Therefore, I would choose to operate LOP at high MAP and very low RPM not to stress the engine.
To me it is all about smart engine management using today’s technology, resulting in low CHT’s, low oil temps, clean exhaust gases and finally economy.
Again, this is only possible with a conforming engine.
To return back to the thread, over time ignition and induction components change, this is likely what also occured to your engine, it is very unlikely your injectors changed in your scenario.
over time ignition and induction components change, this is likely what also occured to your engine, it is very unlikely your injectors changed in your scenario.
I agree, but what could have changed? The mags have always come overhauled by QAA in Tulsa (the best company I know of), the ignition harness was new in 2002 and in 2008, the plugs are iridium and I clean and check them personally, the induction system is just a pipe with some valves at the end of it 
Re your earlier comments, I agree too, but in practice with a non-turbo engine there isn’t any choice because in my situation one flies either VFR (low level, 23" all the time, slightly LOP, and the flights are usually short anyway) or IFR (and one runs out of MP at all normal Eurocontrol levels).
It is only at low Eurocontrol levels, say FL100-120, that one can play with it, and that is where 2200rpm with deeper LOP seems to produce a few % more MPG. But that flight is still with a wide open throttle, as is anything above ~FL080.
How about the fuel lines? Did anything change, such minor re-routing, or perhaps a fuel flow transducer moving a bit? I would guess that the actual amount nozzles would be quite sensitive to small changes in pressure.
Nothing I can think of, except the fuel distributor on the top of the engine. That is original. But this “situation” has been very consistent.
