/ My garden tractor is 26hp, my scut tlb is 22.5, how come? #11
So if I understand correctly, hp is primarily linked to top speed, but not necessarily torque?
I'm sure this has been answered before, but just gimme the quick&dirty. Why scuts are powered less than some garden tractors?
Here is the performance curve from a Kawasaki FD711D (a high-end water cooled 2 cylinder gasoline engine. This engine is probably rated at 25 or 26 HP. While it can support that (@3600 RPM) it can't do it continously.
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Here is the performance curve from a Kubota D1105 (a water cooled diesel engine used in some small tractors). Notice how much less the torque drops at higher RPM, but the more important line is the NET CONT one. This one shows that it can output over 14HP @2000 RPM (or almost 22 @3000) all day long. The gas engine shows 10HP @2000 and just over 14@3000. So, the diesel when it is just above idle can ouput as much power as the gas one at almost full throttle.
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Gearing can make up the difference in the top RPM difference between gas and diesel. But, diesels are known for being able to make significant power at lower RPM. Torque * RPM = Horsepower. So, it really is all about making more horsepower at lower RPM for longer periods of time. Depending on the job, you might or might not need all that power (torque). For a lawnmower, most of the time it is mowing average grass and does not need that much power to do it. But, if you let the grass get really long and are mulching, the horsepower requirement will increase dramatically. A diesel is likely to handle that much better than a gas engine.