MossRoad said:
One thing to note...
The Kohler 22HP engine makes 22HP with two cylinders and 41 cubic inches of displacement.
The Kubota 22hp engine makes 22HP with three cylinders and 54 cubic inches of displacement.
Thats around 30% larger displacement. Not really a fair comparrison. Find a diesel that is 41 cubic inches and two cylinders and compare the HP and torque charts for a fair camparison (in my humble opinion, of course
).
Moss, Nice to hear from ya!
In reading this thread and following the links in it and the other T vs H threads there was a point made. It was in one of the links, I think. The test procedure for an engine like the Kohler is not the same procedure as for the Kubota. The Kohler is tested with no exhaust or muffler, no air cleaner, no fan and no maybe even load. Someone (in a thread IIRC) said that they can actually "test" by a calculation. Sort of a vertual test if you will.
The Kubota is tested with air cleaner, exhaust, accessories etc. That is a LOT of difference. I would guess that your Kohler is about 15-17 hp if tested in the same manor.
{Ha! Found the link.
Diesel vs Gas }
From the link.....
The images above are the torque and horsepower curve from a 22hp Kohler Command engine just like is used in a vast majority of consumer and light commercial products. The Kohler engine reaches its peak 22hp at 3600 RPM. However a quick glance at the torque curve shows that its only able to muster a 32 ft lbs of torque at that speed. When put under a light load the engine is unable to maintain its speed and will progressively slow down and loose power. Its torque will peak at 37 ft/lbs @ 2400 RPM where it generates 17Hp, slipping much lower will case it to stall.
The Kubota diesel engine shows totally different results when put under load. Just like the gas engine, a diesel has less torque when running at full throttle, however the results under load are not nearly as dramatic. At a full 3600 RPM the engine has about 37 ft lbs of torque, a worst case scenario, but still more than the Kohler can muster under any circumstance. When pushed hard and slowed back to 2400 RPM we are still left with 19.5 Hp and 41 ft lbs of torque. Given the torque difference its going to take much more strain to bring the engine to this point and even more to bring it to its knees. To go back to the wrench example, the diesels wrench does not shorten as quickly when you push on it.
Honesty in Specification
Another issue that is largely ignored is the way in which these engines are ratted. These companies realize that consumers are easily swayed by horsepower ratings and so they do their best to always stay ahead of their competition. Kohler bench tests using the "SAE J1340" standard which has no air cleaner, exhaust, charging, cooling or fuel pump. Once the tractor manufacturer adds on the rest of the components a substantial drop in performance occurs that skews our conclusions seven further. By using Kohler's bench test instead of real world performance the tractor company can make it appear as if they have more power than they really do. This is a very common practice and can be easily spotted on spec sheets where "As ratted by the manufacturer" is in fine print. Kubota used the "SAE J1349" standard which includes standard accessories needed for real world use. We can assume that our engine performance data from Kubota is the same as what we would find in a production tractor. You will also find that Kubota's 22hp engine is actually capable of producing 25hp if its RPM's are further increased. While this would provide good numbers on paper, real world performance would suffer as this engine is commonly used for more demanding tasks (Kubota's own
BX2230) where high torque is more important than high horsepower.
So you see, it really isn't a fair comparison. But not the way you thought. The Kohler "cheats" by testing to a different standard. They also don't note if it is continuous or intermittent power in the curve. My guess is intermittent as that is the higher number.
jb
