Tractor VS Industrial HP
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Daren Todd
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Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
I may not have this right, but from what i've read, tractor horsepower is rated off the pto, so you may have the same horesepower at the engine, you lose some power through the transmission. Where as industrial applications are usually just rated on the actual engine horsepower and is usually installed as a direct drive with some sort of coupler. I'm sure someone will correct me if i'm wrong 
Can't say if current practice is different, but last time I looked into this a good reference was Nebraska Tractor Tests by Univ Nebr.
NTT has been doing this series on virtually every model of tractor since the '40's or '50's. Don't know if they've done Kubotas or not as haven't kept up with the testing over time.
My memory is that NTT did an engineering-based energy-expended calculation based on the machine's ability to drag a standardized weight on a standarized track while measuring fuel consumption, tire slip, and other aspects, all with the machine carefully instrumented and weighted to book specs.
At the end they came up with "drawbar" horsepower and "PTO" horsepower and compared both to the manufacturer's stated horsepower. Seems like the manufacturer's stated HP was always a bit optimistic compared to reality. Note neither drawbar- nor PTO-horsepower is same as if measured by a dynomometer at the engine's output shaft. In later years NTT may have started using dynomometers, I just don't remember.
Not sure what you'll find but the process of determining horsepower might be instructive regardless of the specifics.
For 'older' models of all machines your local library may have a copy of (or can obtain for your use) NTT's book that gave a synopsis of machines tested up into the mid-90's or so.
Please post back with your observations and what you learn so we may all become more familiar with our machines.
NTT has been doing this series on virtually every model of tractor since the '40's or '50's. Don't know if they've done Kubotas or not as haven't kept up with the testing over time.
My memory is that NTT did an engineering-based energy-expended calculation based on the machine's ability to drag a standardized weight on a standarized track while measuring fuel consumption, tire slip, and other aspects, all with the machine carefully instrumented and weighted to book specs.
At the end they came up with "drawbar" horsepower and "PTO" horsepower and compared both to the manufacturer's stated horsepower. Seems like the manufacturer's stated HP was always a bit optimistic compared to reality. Note neither drawbar- nor PTO-horsepower is same as if measured by a dynomometer at the engine's output shaft. In later years NTT may have started using dynomometers, I just don't remember.
Not sure what you'll find but the process of determining horsepower might be instructive regardless of the specifics.
For 'older' models of all machines your local library may have a copy of (or can obtain for your use) NTT's book that gave a synopsis of machines tested up into the mid-90's or so.
Please post back with your observations and what you learn so we may all become more familiar with our machines.
85Hokie
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Daren,I may not have this right, but from what i've read, tractor horsepower is rated off the pto, so you may have the same horsepower at the engine, you lose some power through the transmission. Where as industrial applications are usually just rated on the actual engine horsepower and is usually installed as a direct drive with some sort of coupler. I'm sure someone will correct me if i'm wrong
most places give you BOTH , raw horsepower (gross) and pto hp, pto is typically 20% or more, less than engine hp due to all the stuff it has to go through to turn.
Also usable HP on a gear machine is a little bit bigger than the same engine that uses hydraulic tranny. Potential HP and usable HP are a horse of a different color too!
North Idaho Wolfman
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One reason is hydraulic pump operations.
On an industrial engine normally the hydraulic pump is powered by the crank as an accessory or power plant for operations.
On tractor engines it's integrated into the engine and soaks up power before base HP is calculated at the crank.
Another factor with most Kubota engine models, is that there is optional or different parts used to build a motor, and those options and parts effect the base HP of the motor.
It's not that uncommon that several motors of the same CC / CID to have different HP's just based on the parts bolted on or in it.
Look at a simple Chevy 350 / 5.7 motor, I have seen ranges from 125HP to 700+HP, just by changing parts.
On an industrial engine normally the hydraulic pump is powered by the crank as an accessory or power plant for operations.
On tractor engines it's integrated into the engine and soaks up power before base HP is calculated at the crank.
Another factor with most Kubota engine models, is that there is optional or different parts used to build a motor, and those options and parts effect the base HP of the motor.
It's not that uncommon that several motors of the same CC / CID to have different HP's just based on the parts bolted on or in it.
Look at a simple Chevy 350 / 5.7 motor, I have seen ranges from 125HP to 700+HP, just by changing parts.
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Daren Todd
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Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
I didn't realize they showed bothDaren,
most places give you BOTH , raw horsepower (gross) and pto hp, pto is typically 20% or more, less than engine hp due to all the stuff it has to go through to turn.
Also usable HP on a gear machine is a little bit bigger than the same engine that uses hydraulic tranny. Potential HP and usable HP are a horse of a different color too!
most of what i deal with is the actual hp on the industrial side. You need a 30 hp motor to run a gen end, or 280 hp to run a pump end, ect. i was gonna go into a little more detail this am, then got side tracked with a honeymoon booking emergency for my daughter at least she's breathing again Good info, i'm always trying to learn something new
It's common to have the same engine with different HP ratings. Probably the difference between them is one has more fuel turned to it or maybe a few extra rpm's.
A friend of mine has 2 JD tractors, both with the same engine but one is 85 hp and the other is 105 hp. C15 Cat engines go from as low as 275 hp up to 600 hp, just depends on how much fuel is turned to them and which turbo system they have.
A friend of mine has 2 JD tractors, both with the same engine but one is 85 hp and the other is 105 hp. C15 Cat engines go from as low as 275 hp up to 600 hp, just depends on how much fuel is turned to them and which turbo system they have.