Continuous duty is about output, not RPM
Thanks, another question.
Continuous Duty Rating .........FWHP (kW)/rpm 140 (104)/2200
I am surprised that the continuous duty is 2200rpm out of 2400, or 91.6%. It seems very high to me. Is there a design reason for this? Or am I not understanding it correctly?
Yes, this is a (very common) misunderstanding.
Don't think in terms of
"percentage of RPM". Look at the
horsepower rating. Your maximum engine rating is 174hp, and your continuous duty rating is 140hp. That's 80.5%, which is very typical for this class of engine.
One of the biggest 'conceptual humps' to get over when working with diesel engines is the idea that there is a hard relationship between RPM and horsepower, or RPM and Fuel Burn. Neither is true. You have to add torque into the equation.
The best way to break yourself of this is to always remember that (a) engines
always burn fuel in proportion to the
horsepower they are making, and (b) that horsepower is
always Torque x RPM.
So...let's exercise this concept. Take your engine and spin it up to 2,200 rpm with the transmission in neutral. Because there is no external load on the engine, the engine is producing very little torque (near zero) and therefore is producing
almost no horsepower. At 2,200rpm in neutral, you would find that you are burning very little fuel, almost the same as if you were at idle. It takes very little energy just to spin the crankshaft...
Now, let's put your engine in gear while tied securely in your slip. Spin the engine up to 1,100RPM...now you are torquing the engine against the prop, producing something like 40hp and burning something like 2-3GPH.
You have cut RPM's in half but you are burning 10x the fuel!
Hope this helps...