Thread: Under propped?
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Old 03-17-2014, 05:29 PM   #35
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City: Gloucester, MA
Country: USA
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Originally Posted by Brooksie View Post
Additionally, the chart that TT provided us with is not a really good example because that engine produces about the same hp from 2100 on up. A more typical NA engine would not have the flat area at the upper end of the curve. If TT were to overprop to where his new red line is, and limit his RPM to that point (usually reseting the stop on the pump) he would, in his case be giving up very little HP because the curve is so flat at that point.
I think that power curve is pretty typical. Attached is another one from a Deere 6090 rated for near continuous operation. The same engine rated for continuous duty has the same curve shape.

But your point is taken about the HP being nearly flat after the engine reaches peak torque. There is an argument that says you should prop to intersect the line at peak torque (and not go over). What I don't know is what happens to engine life expectancy when you run at the Crankshaft power curve rather than the Propeller power curve. I image it must go down or we would all be propping that way.
Attached Files
File Type: pdf Pages from 6090AFM75_B_M2_AP.pdf (396.8 KB, 30 views)
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