I appreciate that torque and HP are essentially the same, such that
one curve can be derived from the other. It was a revelation that
this conversion can be derived geometrically! However, is it really
true that given two points you can get the full story? What if the
torque peak and HP peak came close together, say at 2500 rpm; then you
would have little info as to how it behaves at 1200 rpm.

Or, using these curves as an example, the straight line approximation
between the two points may be valid, but it says nothing about what
happens outside this range.
http://www.yanmarmarine.com/products...5_TechData.pdf

I'm not trying to debate, I really want to know how to make use of
these curves.

jeff

Matt Colie wrote:
Skip,
As an engine professional for many decades I can tell you that all you
need is the two published numbers I hope are in the engines specifications.
That would be the torque peak and speed and the horsepower peak and speed.
For a naturally aspirated diesel this is very close to what a dyno test
would give you.
Turn the HP back into torque (rev*tor/5252=hp)_ and plot it out as two
straight lines (it isn't, but it won't matter much). If I can find it
and you are interested, I could try to post the one page explaination of
this.
Ta Da - power curve

Matt Colie - still trying to get out of Detroit and back to tidal water
after 30+ years.