Thanks Marty. As soon as I can I'll brush up on minimizing my clutter - sorry.
For now -
Gary LaPook - "Take a close look at note 5 of TCDS E-143, which I have attached. You will see that there is NO increase in power when higher octane fuel is used. The engine was designed and certified to put out the full takeoff power rating of 600 hp using 80/87 fuel. Note, that in order to get the same 600 hp using 91/96 octane fuel you must increase the manifold pressure a half an inch compared to setting takeoff power using 80/87. By the end of WW2 there were four grades of avgas, 80/87; 91/96; 100/130 and 115/145 so "91/96" does not mean 100 octane in the TCDS."
And again, "increasing octane does not increase power" anyway - it merely allows one to safely apply power settings that create the highest combustion chamber pressures - to obtain the highest power output. How? By resistance to detonation and preignition that is more prevalent in the use of less-buffered / more volatile fuels.
Consider Note 5 again - it says (verbatim) -
(a) Ratings are based upon the best mixture strength and 450F cylinder head temperature.
(b) With the use of grade 91/96 fuel, the following ratings may be used:
Maximum continuous, hp, rpm, in.Hg., at:
- Critical altitude (ft.) 550-2200-33.0-4500
- Sea level pressure altitude (ft.) 550-2200-34.0-S.L.
Takeoff (one minute), hp, rpm, in.Hg., at:
- Critical altitude (ft.) 600-2250-36.0-2300
- Sea level pressure altitude (ft.) 600-2250-36.5-S.L.[/u]
LTM -
However, the main data on page 1 states, verbatim:
Maximum continuous, hp, rpm, in.Hg., at:
- Critical altitude (ft.) 550-2200-32.5-5000
- Sea level pressure altitude (ft.) 550-2200-34.0-S.L.
Takeoff (
five minutes), hp, rpm, in.Hg., at:
- Critical altitude (ft.) 600-2250-35.5-3000
- Sea level pressure altitude (ft.)
600-2250-36.0-SL (See note 5.)
There are three ways to show that your interpretation is in error. First you claim that the 91/96 octane is only needed for 600 hp takeoff power but note 5 also shows power settings for continuous power. If you were correct, then by your logic, 91/96 was also necessary for the continuous rating of 550 hp.
Second, note 5 shows a higher mp necessary, 36.5 inches, to obtain takeoff power using 91/96 compared to only 36.0 inches on page one. Just what do you think the 36.0 inch setting on page 1 is referring to? It is referring to the use of 80/87 to obtain takeoff power. If this were not true then page one would omit a power setting for full power and simply refer to note 5. I pointed out the difference in manifold pressure settings in my prior post, I'm surprised that you didn't pick up on this.
Third, note that the time limit for takeoff power is one minute when using 91/96 (note 5) while the limit when using 80/87 for takeoff shown on page is five minutes. Again, this would be omitted if you couldn't produce takeoff power with 80/87. And the lower time limit when using 91/96 makes sense since you are using a higher mp.
gl