Kubota Gross HP vs Net

[Agrantina]

Just crossed my mind when looking at some other brands and their HP ratings. I noticed that Kubota has a Gross HP rating and then gives a Net HP rating. John Deere just gives a Gross HP rating only, while New Holland says engine power? Whats the difference in gross and net? HP rating off the motor vs thru the tranny rating?

What they trying to hide?

AndyG

 

[PHILIP8N]

See attached Kubota engine spec sheet, look at definitions at bottom, see if this helps. In the industrial engine world, intermittent power is defined as the max power the manufacture will allow you to use for one full hour without interuption in reduced power, followed by one hour with the engine operating at or below the continuous hp, with engine hours not exceeding 3000 hours per year. Continuous power is defined as the max power the manufacture will allow you to use for a contstant load application with a 100% duty cycle, with engine hours exceeding 4000 hour per year. This has to do with warrantly and life expectancy of the engine. Gross is without fan, air cleaner, and muffler. Net is with fan, air cleaner, and muffler. In the case of your L3240, how I interperate this, Kubota is saying your L3240 engine makes a gross intermittent hp of 34, has a net intermittent hp of 32 which can be used for 1 full hour followed by 1 hour at or below the continuous curve not to exceed 3000 hours per year, and has a continuous hp of 27 that can be used 100% of the time without interruption for over 4000 hours per year. In the industrial / stationary engine world (where I work) this makes more sense where we rack up thousands of hours per year. But, we still need to know how to compare gross, net, and continuous between manufacturers, as you have noticed. Philip.

 

[Baby Grand]

Parasitic losses. IIRC, Net HP = Gross HP - all of the losses up to the flywheel (alternator, hydraulic pumps, water pump, muffler after the manifold, polution control, etc). I don't think it deducts driveline losses. I think that would be Drawbar HP.

I see Philip8N beat me to it with much better info. Dang.

 

[RADIUM]

My father always taught us PTO horsepower is important that's what you really have for the work at hand, if you notice most equipment gives PTO horsepower recommendations not engine horsepower take care

 

[LD1]

My father always taught us PTO horsepower is important that's what you really have for the work at hand, if you notice most equipment gives PTO horsepower recommendations not engine horsepower take care

+1.

Most older tractors didn't even bother to give an engine HP. They only gave PTO HP and drawbar HP, because those are ther two that actually matter.

 

[Agrantina]

Thanks Phil--- It is clear as mud now.. Well not really I understand the diff now, SO the next question is why doesn't Kubota give a draw bar HP? It looks like the draw bar rating would be a few less than net HP... It just seems funny to me with ALL the different manufactures how each one posts a different spec on their machines HP rating. Their are ALOT of CUTs that have 2-4 HP difference...

Can one really tell 2 HP difference? I still say WEIGHT has alot to do with HP to the ground!!

AndyG

 

[PHILIP8N]

SO the next question is why doesn't Kubota give a draw bar HP?

I think because no one is doing field tillage work with L3240's, L3940's, L5740's. I have only seen drawbar horsepower listed on older ag farm tractors, where weight has a great effect. Drawbar hp is the horsepower avaiable to pull, taking engine power, weight, tire slippage, etc, and putting that into a horsepower available to pull. Search Nebraska tractor testing for more info. What is probably most important as a fair comparison, as stated above, is pto hp. Philip.

 

[rbargeron]

... It just seems funny to me with ALL the different manufactures how each one posts a different spec on their machines HP rating. .................I still say WEIGHT has a lot to do with HP to the ground!!....

In the old days, tractors were rated as 1-bottom or 2-bottom or 3-bottom etc. reflecting how many plows they would pull. That gave way to rating them by pto horsepower (power available to do useful work). But higher power sounds better to customers so the marketing people started counting every last drop of power made - including air pumped by the fan, noise made, heat generated, etc. in the effort to out-do the competition. There were only loose standards by gentlemen's agreement. As more off-shore manufacturers entered the game things got worse - but eventually the industry sorta standardized on the "net hp" rating. Thing is, even that is not a rigidly enforced standard so precise comparison is still approximate. And you are spot on - without the weight to couple it to the ground, potential power's value is hard to measure.

With all that said, I still stand by by old TBN signature "Power is Good - So is Weight"

 

[rScotty]

Whats the difference in gross and net? HP rating off the motor vs thru the tranny rating?

What they trying to hide?

AndyG

Wow! Isn't it interesting statement about our society when we automatically assume that advertisers are trying to hide something rather than give us more information.

I'm reminded when one of my buddys came and asked how in the world could a Sears air compressor be rated at more HP than the wall socket could put out. The answer is that it actually can, but sure enough it's a trick.

In the case of tractor motors, GROSS HP is supposed to be what the bare engine puts out even though nobody uses any engine that way. And NET HP is the usable HP that actually travels though the transmission and does work on the ground while also turning things like the fan, alternator, and hydraulic pump. So you brag on Gross and figure with Net. The difference between the two keeps engineers employed.

Frankly, HP isn't what tractors are about anyway unless you care how fast you can go at full load. With enough gearing, even tiny tractors have more than plenty of HP. The limiting things are more likely to be weight, stability, and traction.
Good Luck, rScotty

 

[crazyal]

I'm kind of surprised that they don't give torque numbers.

 

[Agrantina]

With as many different brands as there are for CUTs under 45hp I figured most of the ratings where for competition between brands.. Yes it is amazing what weight will do in the right places on a tractor. The 3240 I have pulls a disc way better than the 7 HP more older tractor I was use to.. 4wd and about 1200lbs makes WAY more difference than 2wd and lesser weight..... I do like the draw bar HP rating- but as Phil stated most CUT use PTO HP more than draw bar power...Yes I am getting a tiller and may retire that old 7ft disc!

AndyG

 

[PHILIP8N]

I'm kind of surprised that they don't give torque numbers.

Torque can be calculated from hp. TQ = (HP x 5252) / RPM.

Philip

 

[PHILIP8N]

I'm kind of surprised that they don't give torque numbers.

Here is the complete curve for your L4240. Philip.

 

[Agrantina]

Phil- where did you get that? I have the babyG L3240... In my hot rodding days HP was speed and Torq was calc in how many sets of rear tires you went thru :laughing:

AndyG

 

[PHILIP8N]

where did you get that? I have the babyG L3240:
AndyG

Here is the curve for the L3240. You may be able to find online, but we use alot of Kubota, Deere, Cummins, and Cat engines here where I work, so I had the referance data on hand. Philip.

 

[Samandothers]

Phil
THanks for info on HP for L4240 also the HP education.

 

[Haywire]

I'm kind of surprised that they don't give torque numbers.

Yea, all the small lawnmower type engines are rated in torque instead of HP now. I heard that was mandated due to mfgs fluffing their numbers. When I was a kid, a 22" cut 3.5 hp mower would really lay down the grass. The last push mower I bought claimed 5hp I think and it was down right disappointing.

Ian

 

[bigbull338]

your gross engine hp is based on 2500rpms.the pto hp is usually 5 to 10hp under the engine hp.

 

[PHILIP8N]

your gross engine hp is based on 2500rpms.the pto hp is usually 5 to 10hp under the engine hp.

This is an extremely vauge statement and would not consider it standard for any comparisons. Are you talking about one specific model or for every tractor in general? Philip.

 

[kuboman]

Gross engine hp is basically meaningless. As a rule pto hp is about 15% less than gross power and draw bar hp is 15% less than pto whether you are talking 20 hp or 200hp.