TSO
Elite Member
I've taken the liberty to put in some paragraphs in your reply. I hope the changes don't distort anything you said.
You mention a 37hp and a 66hp tractor but you don't state specifically whether they are on the same frame size (I doubt it). There is no question that a larger frame higher horsepower tractor will do more work than a smaller frame lower horsepower tractor. Nobody here is disputing that. However, the issue being debated is the relative advantages of more or less horsepower with the same size frame, identical loader, tractor weight almost identical, and identical hydraulics. As best I can tell the only difference other than horsepower is tire size.
The engines for the NX4510 and 6010 are based on the identical 3 cylinder block and are both naturally aspirated according to Kioti's website. Of course Kioti has never been able to get their website accurate and today both the 45hp and 60hp variants are listed as having the identical 1.8 liter displacement. I rather doubt that is accurate. The other guys here claim to know a lot more about those engines so maybe they can fill us in. I've looked on Kioti's website for the specific fuel consumption graphs for the NX engine series. Nothing to be found and they have even removed the charts they used to have posted for the DK line engines. The general principles are the same with diesels however so a chart demonstrating specific fuel consumption for a Yanmar marine engine is informative. I've posted the jpg below. It basically shows that diesel engines use MORE fuel per kilowatt of power produced when run at LOWER rpm. Running an engine designed to put out 60 hp at 1500rpm to produce the same power as a 45hp engine running at 2000rpm will show that the 60hp engine uses more fuel to produce the same power.
I'm all for efficiency but I don't know of examples of higher horsepower diesels that are equally efficient at the same output. Bigger pistons, bigger bore, more friction surface has to waste fuel when not running at optimal engine speed for efficiency. More important, if diesel engines have their most efficient output close to PTO RPM, then a more powerful engine doing the same work as a smaller engine is going to be operating in a suboptimal RPM range for efficiency. I'm not an engineer but that just stands to reason. Also, while some folks here claim that you would expend the same amount of fuel running a mower with either a high or lower hp engine, it seems impossible to do that unless you run the more powerful engine at a lower RPM. You cannot do that when mowing and expect the same cut. Mowers are engineered to give their best cut at PTO speed. That means if the lower HP engine will be running at PTO speed for a given HP while the higher HP engine running the same mower will be running at significantly lower RPM. Of course the higher horsepower tractor should simply be running a larger mower but that has consequences too. The difference between a 6ft medium duty bush hog and an 8ft medium duty bush hog is a couple of grand last I checked. Pretty much the same story with other implements too. Bigger implements might be desirable but there are good reasons why the vast majority of TBN tractor owners tend to top out at about 6ft implements. If you really think eight foot implements make sense then 60hp might make sense. It would be inefficient however to run six foot implements with a bigger engine than necessary.
With regard to rototilling or discing, horsepower certainly can make a difference in the size implement you can use. For rototilling, 40hp seems fine to run a six foot tiller in my experience. I rototill in low range can can break new sod, wet or dry without even running at full PTO speed. I'm sure a seven or eight foot tiller would require more horsepower. It will also cost almost double what a six foot tiller costs. If you are a commercial farmer that cost may well make total sense. Most folks on TBN are not using their tractors for commercial purposes full time so that calculus is tougher to justify especially for an implement that gets used once or twice a year as with a rototiller.
Mowing seems the area where more HP might well be justified so long as the appropriate size mower is used. As a 40hp does fine running a six foot bush hog, I'd imagine similar efficiency would dictate an eight foot bush hog for a 60hp tractor. Pretty steep price jump from 6ft rotary to 8ft rotary of similar duty rating. Again, for commercial use it might be easy to justify but most TBNers buying Kioti DK or NX size machines are not commercial operators.
I've never run a 3PT stump grinder. I note however that a hydraulic $38,000 Vermeer stump grinder uses a 34hp diesel engine. . A 24" wheel 3pt stump grinder model uses max of 35hp and cuts 10" below grade. A pro 34" model cuts 12" below grade and runs on 35-100hp....why stop at 60hp???
Your comments on pushing trees over and use of the loader are just wrong IMO. The NX tractors are all the same weight and have the same loader. You bent (!!!) an FEL arm on your tractor which shows that even a 37hp tractor can produce damaging amounts of force when used inappropriately on a tractor FEL. Tractor FELs are designed and manufactured to lift not push. We all push with them but clearly there is a reason bulldozers have short fat FEL arms rather than long skinny ones like on a tractor. Having more HP available to push might well allow more force to be exerted against a tree but it is a dangerous thing to do. I've pushed over many trees with my 40hp DKse, not sure I'd want to put even more force on the identical loader (different number same loader ) with an NX.
My bottom line: if you really need 60hp for something other than a larger mower, get a bigger frame tractor. Putting 60hp into the NX frame is akin to putting 500hp into a F150. Very limited returns. Get a F250 instead.
Yes, and no. There are other factors than size. Trans options also factor in. But you're right that it depends on the user and tasks.
For me, aside from my own use, which is managing only 15 acres and a very small "farm" (small livestock and just a couple acres of cash crops)... I work my tractor commercially. I truly need more HP, but I also need to be as small as possible, for access limitations, transport, and ground impact.
I have an 8ft belt driven dual blade b'hog. When I did a couple big jobs last year, I'm sure glad I had the extra width! That one doesn't really bog down the tractor because the belts will slip as the blades encounter something too thick, but if I tightened the belts, then the tractor HP would definitely come into play.
Regarding a stump grinder, a Vermeer commercial grinder engine really only has to worry about the hydraulic pump. It's not powering a tractor. And the hydraulic output is likely much higher than a CUT. So, you really can't compare that. I don't know how much more PTO HP would completely "future proof" my 3pt grinder, but I do know that 36.5 works well on soft wood, and relatively seasoned hard wood, but isn't enough for newer hard stumps, especially large ones.
When grading, I like to grade in medium range. The speed of medium leaves a nicer finish than going in low range, and obviously make much quicker work of it. Sometimes I could use more HP. But again, I don't know how much.
That's what has stopped me from selling my 1648... I just don't know how much HP would be enough.
Again, I'm sure that for some people, they have more HP than necessary... But I'm also sure that the vast majority of tractor owners who regret their purchase, regret not having more power, or more size. I know for me, the size is perfect, and I love the loader strength... I just need more HP.
I wonder if I could drop in about 75 HP ?!?!