RCU Forums - View Single Post - Overloading an engine

10-10-2008 | 05:25 PM

#28

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: Overloading an engine

Quote:

ORIGINAL: gkamysz

Guessing HP curves from prop values is useless unless we know exactly how much power the prop requires. Take Dar's example above. The peak HP value appears to be the same however it's 800 RPM(really 1,600 RPM) different with different props. The engine is not changing it's torque curve. The above only proves that the prop constants, or pitches are not accurate. This engine's peak torque should occur near 2,500-3,000 prop RPM. It should not be at 4,400 RPM like this indicates.

Greg,

While it may be more accurate to measure an engine's torque using torque beams, Pé Reivers calculator is being made more accurate, as it is updated by him.

The torque curve of nearly all engines, is not as 'smooth' as some full-size car manufacturers want us to think...

Torque is affected by many variables and the outcome is a rather bumpy curve...Not only are there global peaks and dips, but there are changes on a smaller scale, which may bump the torque up, or down, by 10% and more, over a span as small as 100 RPM.

Please check out David Gierke's large .60 engines shootout in MAN 05/03, for torque curves plotted using 'torque beams'.

Smooth is a rather inaccurate description of all of them.

And you are right. The torque curve does not change. At the same RPM (at full throttle), the engine will consistently make the same torque...
But if you change the RPM, the value could change.

None of the props showed the same RPM as another... as this would have indicated a change in the torque curve...

But even a rather small RPM change; from 4,400 to 4,450, caused a drop of 8% in the value of the torque... It can happen.

And, I am totally not sure this engine really shows its peak torque at 5,000-6,000 crankshaft RPM.
...And Juice did not supply a prop and an RPM that would substantiate your bold claim...

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