Importance of Engine Displacement when Comparing SCUT/CUTS?

   / Importance of Engine Displacement when Comparing SCUT/CUTS? #11  
HP for moving the tractor around isn't that much of a discriminator when comparing tractors in the same general range. Case in point, Kubota makes a 26HP BX2680 SCUT and a 26 HP B2601 series tractor. The B is a physically larger tractor and has more capability but same engine HP. Why? Because its less about engine HP and more about the size and flow rate of the hydraulic pumps and PTO HP.

Tractor speed and torque can be optimized with transmission gearing. With HP rating at the PTO.....Will you run PTO driven implements? Typically, higher engine PTO equates to higher PTO HP. That said, mileage varies. Kubota has efficient engines that put a higher percentage of engine HP to the PTO shaft. JD tends to have more HP loss at PTO relative to a engine HP.

With autos we are led to believe more HP is better. With tractors that not necessarily the case.
 
   / Importance of Engine Displacement when Comparing SCUT/CUTS? #12  
There are quite a few points to talk about here so i'll choose 1 to speak about displacement/horsepower.

Some people will tell you the days of large displacement is over and it doesn't matter, it's a little more complicated than that. Let's assume we are looking at engines with equal HP. More displacement is usually going to result in horsepower at a lower rpm and more torque at a lower rpm which will make the tractor feel much more powerful and allow it to more affectively use ground engaging implements and the loader. For PTO implements it's not going to change much.

The caveat here is forced induction(turbo), with the right sized turbo you can have a smaller displacement engine that makes the same or more horsepower without having to run very high rpms. This allows the smaller displacement machine to act a little more like its larger displacement competitor. The issue here is usually turbo lag which is basically the time it takes for the turbo to spool up and during this time engine power is underwhelming. This again gives an advantage to the Naturally Aspirated Larger Displacement engine, it has lots of power at a low rpm all the time and never has lag while waiting for a turbo to spool or doesn't need to wait for a small displacement engine to get the rpms way up high.

A quick example is my Kubota m5700(62 HP naturally aspirated) vs my cousins New Holland workmaster 70(70hp turbo charged).

My Kubota has a 168 cubic inch engine with 62 hp The NH has a 136 cubic inch engine with 70 hp turbo charged. Due to the turbo in the NH its actually rated at a lower rpm than the kubota but due to the smaller engine displacement and the turbo needing high rpms to really shine it kind of struggles at low rpm. When pulling a plow or running the loader the kubota actually feels more powerful and is easier to operate without bogging down since it has more torque at a lower rpm. Now once you are at MAX rpm the extra 8hp the NH has is noticeable if you are pulling a heavy disc or plowing a wet field or mowing tall grass. But for loader work, starts and stops, gear shifts etc the kubota is a little more "driveable and forgiving". Kinda splitting hairs here both machines run great and have plenty of power for their weight. But if you compare that workmaster 70 to a 70's vintage 70hp farm tractor the difference would be even more obvious.

Hope this makes some sense and isn't just a confusing mess or words.
 

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