Thank you again to you, Sergeant and Darryl!
Do not be sorry Darryl, my problems are not from you, but rather from my weakness with english.
I must admit I need help from an online translator and dictionnary to understand you and also write my answers ...
I read each of your answers dozens of times before my pc, or in the subway ...
I realize that theoretical knowledge base is lacking.
So thanks for taking the time to explain to me like you do.
Darryl, first of all I think I understand the concept of optimum climb, similar to the car.
I can actually uses more fuel with high power, but as we'll rise faster at cruise altitude, there's gain.
I think I understand also that all parameters can not be locked because with the altitude, the cards changes.
Most often the boost (or if necessary the speed) should be adjusted to keep constant the other parameters, rpm and rate of climb.
Finally, a high cruising speed is better.
An aircraft operates efficiently at high altitude at high speed.
This is consistent with your words, Seargent.
Cruise in altitude allows proper cooling.
Low rpm and high boost can generate more heat, and slower coolant flow, resulting in improved temperature maintenance.
That said, I often harder to adjust my needle cooling at "nine o'clock position", because it is rather closer to ten hours than of seven...
Actually, I had forgot that I can reach the required boost without opening full the throttle, as at take off.
But we are still not far from the maximum opening with a MK1, with +6.5 psi at low altitude, right?
Because without the extra boost (small red push lever) that I never use, the Merlin of Mark1 hardly reaches more than +7psi is that correct?
That said, for me it there's a major misunderstanding in your example, Sergeant.
I read you, I reread you, and I finally find that I am not competent.
You say +6 psi of boost throttle not completely open like as take off, delivers less power than +6 psi of boost throttle fully open?
In your last answer, you try to explain myself, but I can't understand, that it causes a deficiency of power as we can not fully open the throttle for the boost required!
But yet the power is proportional to the intake pressure at constant rpm, no?
This difference come from just a poor filling of the cylinder when the throttle is not fully open?
Or it there's something else I'm missing?
Why with the same boost, it does better with the throttle fully open rather than an incomplete opening?
Why do we consume less at equal boost (and rpm), with the throttle fully open?
It is incomprehensible to me!
Still, once admitted this conclusion that full throttle opening is better for the boost cruising, I understand why the Spit feels ok at 20,000 feet. It is at this altitude we obtain boost for cruising about +3 or +4 psi, with throttle fully open.
Thank you for your patience ...