Still understanding the implication of different tractor specs

Marlon

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Kubota MX5200HST
May 7, 2022
14
2
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Australia
I've created two posts in an attempt to search for facts and information to help me make the right decisions on purchase, and thank those who have responded and taught me allot, but still haven't seemed to get to the point of my queries.

So, I would like to make one final post before I decide with as simple a question as possible to see if I can get the crucial technical assumption I am working with ratified of rejected.

Looking at lots of specs, most of the tractors of interest have a rated engine RPM of 2600 or there abouts +/- 100 RPM

However, they vary significantly in their specified engine RPM required to turn the PTO at 540 RPM

My assumption is that a tractor turning the PTO at 540 at an RPM way less than the engines rated RPM, will be significantly more fuel efficient than a tractor achieving PTO 540 at the engines rated RPM thus revving its head off, and this is what I want ratified or rejected.

So to get a bit closer to the decision I have to make, forget brand/model, and tell me which of the following two tractors will have significantly better fuel consumption pulling the same rotary cutter through the same pasture growth (given that tractor 1 is currently doing the job but guzzling fuel):.

Tractor 1,
50HP TURBO with Engine DISPLACEMENT 2500cc
Hydrostatic
Engine RPM 2700
PTO 43HP
PTO 540 Speed 2700 RPM (same as the engine RPM)

Tractor 2,
62HP NATURAL with Engine DISPLACEMENT 3300cc (800cc more than tractor 1)
Hydro Shuttle
Engine RPM 2600 (100 less than tractor 1)
PTO 55HP
PTO 540 Speed 2160 RPM (440 less than the engine RPM)
 

GeoHorn

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Tractor No. 2 is the choice I’d make.

The issue with your comparison attempt is that you haven’t posted the torque-curves of those two tractors. The engine-speed vs PTO speed in probably realized at the optimum torque output of the engine. Attempting to separate these two tractors by fuel consumption is not going to be the economical boon you are hoping for.
But tractor No 2 will be working less-hard and all other things being “equal” ….… :rolleyes: ….. will be more dependable. IMO
 

GreensvilleJay

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maybe not HOW you're supposed to think but...
#1, 2500 CC X 2700 RPM = 6,750,000

#2, 3300 cc X 2600 RPM = 8,580,000

#2 is 27% bigger,so more air( and fuel) is consumed
so just using those numbers, #1 should be better.

There's a zillion factors to be considered like tires,traction,HP/T curves, gearing, speed,etc.
Unless there's some kind of 'feedback' from actual PTO load to control the engine 'computer' to maximize the burn,hard to see how 'bigger is better' .
Curious, Are the 'Nebraska Tests' still being done ? If so do they show GPH per PTO load ??
 

RCW

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My intuition would say the 2.5l turbocharged engine will more efficiently use fuel versus a naturally aspirated 3.3l engine of higher horsepower. Tractor 1 would use less gph than Tractor 2 for the same work. But there's too many variables to say that with any certainty. Just a guess.

You say the 2.5l turbo guzzles fuel while mowing. What size cutter? Are you cutting some tall/thick stuff?

Fuel efficiency and actual consumption could be two different things. My truck might be fuel efficient, but if I drive fast all he time, my actual consumption stinks.

Just wondering if it appears to be guzzling a lot of fuel because it's really doing a lot of work.
 
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PoTreeBoy

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I think you're locked in one issue - the engine - instead of looking at the whole system. I suspect the engines have similar fuel burn vs horsepower. The issue is where that power goes after it leaves the engine.

The load on the engine is basically PTO power + motive power.

Ideally, you would have the implement and tractor matched to the job at hand. I think you said earlier that you have 80 to 90 acres to cut and a 6 foot rotary cutter behind an MX5400. We don't know what you're cutting, I have visions of the outback but suspect areas of Australia are much different. Dry, sparse grass is much easier to cut than lush, green grass.

We know the hydrostatic transmission is much less efficient than a gear transmission at converting engine power to motive power. So for your mowing, large open areas (as I perceive it), HST is wasting a significant amount of your power. If I'm wrong and you're using most of the engine's power to cut thick lush grass, the wasted power is less significant.

On a side note, no law says you have to run the cutter at 540 rpm. I mow with a pre-emission Ford, at typically 15 - 20% below PTO speed, cutting fairly thin grass just as well as full speed. I can use a higher gear, giving the benefit (mostly) of 540e. You don't have that option on the MX, since you need to run near rated speed to satisfy the DPF. But with the M6040, you could.

Long story, short recap. Your MX's combination of HST plus DPF may be forcing you to perform your primary mission very inefficiently. IMO, of course.

PS - if you provide us with a little info,
* description of what you're cutting, sparse/thick, dry/lush, mowing low vs topping
* lay of land, how fast can you reasonably drive over it,
it might help.
 
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Henro

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maybe not HOW you're supposed to think but...
#1, 2500 CC X 2700 RPM = 6,750,000

#2, 3300 cc X 2600 RPM = 8,580,000

#2 is 27% bigger,so more air( and fuel) is consumed
so just using those numbers, #1 should be better.

There's a zillion factors to be considered like tires,traction,HP/T curves, gearing, speed,etc.
Unless there's some kind of 'feedback' from actual PTO load to control the engine 'computer' to maximize the burn,hard to see how 'bigger is better' .
Curious, Are the 'Nebraska Tests' still being done ? If so do they show GPH per PTO load ??
BUT #1 is turbocharged, so since more air is being pumped into the engine, more fuel must be going in as well, otherwise the excess air would serve no purpose.
 

jimh406

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Are these exactly the same size tractor? Generally speaking, it takes about the same fuel to do the same work at load. At least, not enough difference to that matters.

If the choice was which is most fuel efficient empty or at elevation, I'd choose the turbo. It gets more complicated once the tractor is actually doing work.

Max RPM is adjustable, so that's not going to be a reliable indicator of fuel efficiency. They could easily limit the RPM of the larger engine. Who knows why it has that much higher RPM. That's not very explainable if they are the same brand.
 

PoTreeBoy

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BUT #1 is turbocharged, so since more air is being pumped into the engine, more fuel must be going in as well, otherwise the excess air would serve no purpose.
That would be true for a spark engine where a stochiometric mixture is needed. But a diesel only injects the fuel it needs, usually running lean.
 

SDT

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I've created two posts in an attempt to search for facts and information to help me make the right decisions on purchase, and thank those who have responded and taught me allot, but still haven't seemed to get to the point of my queries.

So, I would like to make one final post before I decide with as simple a question as possible to see if I can get the crucial technical assumption I am working with ratified of rejected.

Looking at lots of specs, most of the tractors of interest have a rated engine RPM of 2600 or there abouts +/- 100 RPM

However, they vary significantly in their specified engine RPM required to turn the PTO at 540 RPM

My assumption is that a tractor turning the PTO at 540 at an RPM way less than the engines rated RPM, will be significantly more fuel efficient than a tractor achieving PTO 540 at the engines rated RPM thus revving its head off, and this is what I want ratified or rejected.

So to get a bit closer to the decision I have to make, forget brand/model, and tell me which of the following two tractors will have significantly better fuel consumption pulling the same rotary cutter through the same pasture growth (given that tractor 1 is currently doing the job but guzzling fuel):.

Tractor 1,
50HP TURBO with Engine DISPLACEMENT 2500cc
Hydrostatic
Engine RPM 2700
PTO 43HP
PTO 540 Speed 2700 RPM (same as the engine RPM)

Tractor 2,
62HP NATURAL with Engine DISPLACEMENT 3300cc (800cc more than tractor 1)
Hydro Shuttle
Engine RPM 2600 (100 less than tractor 1)
PTO 55HP
PTO 540 Speed 2160 RPM (440 less than the engine RPM)
There is no way to definitively answer your question without real world testing.

That said, tractors with gear type transmissions are more efficient than similar tractors with HST transmissions.

Best guess, Tractor 2 due to gear type transmission and lower engine RPM, but work is work, so I would expect that difference would be small.

SDT
 

SDT

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maybe not HOW you're supposed to think but...
#1, 2500 CC X 2700 RPM = 6,750,000

#2, 3300 cc X 2600 RPM = 8,580,000

#2 is 27% bigger,so more air( and fuel) is consumed
so just using those numbers, #1 should be better.

There's a zillion factors to be considered like tires,traction,HP/T curves, gearing, speed,etc.
Unless there's some kind of 'feedback' from actual PTO load to control the engine 'computer' to maximize the burn,hard to see how 'bigger is better' .
Curious, Are the 'Nebraska Tests' still being done ? If so do they show GPH per PTO load ??
Not sure if NE tests are still being performed but do know that Kubota never sent tractors to NE for testing.

Yes, NE tests do measure HP hours per gallon.
 

Henro

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That would be true for a spark engine where a stochiometric mixture is needed. But a diesel only injects the fuel it needs, usually running lean.
Then why have the turbo charger on the diesel to begin with? If the excess air pushed into the engine is of no use?

Honest question.

Seems logical to me that the extra air is needed for something. If not needed for combustion of extra fuel in a diesel, what is its purpose? How would a turbo charger increase HP output otherwise?
 

BruceP

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This is an interesting discussion. Many knowledgeable folks have rendered valuable opinions.

The OP is obviously concerned with fuel-cost, some generalities might be observed:
  • Tractor engines convert liquid diesel into 'work'
    • In the end, it is the 'work' which consumes the fuel.
    • The efficiency-differences between modern engines may not be significant.
    • Higher engine RPM does not mean more fuel is being consumed.
    • Some modern diesels are smaller-displacement and spin faster to generate the same 'work'
  • 'Gear' xMissions are more efficient than HST.
    • anyone who has dealt with HEAT from HST unit knows where the rest of the energy is ending up 🤔
  • From personal experience, keeping the mow-blades RAZOR-SHARP makes a HUGE difference to lower fuel consumption.
 

Dieseldonato

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Tbh we've beaten this to death in 2 other threads. Get the gear drove tractor. And don't let the turbo of the higher hp tractor be the determining factor.

Then why have the turbo charger on the diesel to begin with? If the excess air pushed into the engine is of no use?

Honest question.

Seems logical to me that the extra air is needed for something. If not needed for combustion of extra fuel in a diesel, what is its purpose? How would a turbo charger increase HP output otherwise?
So short version is the more air you cram into a diesel the better the chances of it having complete cubustion. Yes we use the turbo to force more air to burn more fuel also. Hence making a smaller engine capable of higher ho then a larger engine. Now if we take a look at a naturally aspirated engine we will see that the only air going into the engine is what that atmosphere can push into it. (Hence why at higher altitudes engines make less power, less air pushing into the engine.) At any given load we require a certain amount of fuel and air to be burned. With a NA engine all we have to depend on is atmospheric pressure to get as much air into the cylinder. When the engine is loaded down were still using more fuel to make power but the engine cant get all the air it needs. Hence the smoke and higher egts. Add an appropriately sized turbo and it will allow more air I to the engine helping to get a complete burn of the fuel. This cleans up the smoke and lowers the egts. Now the cool thing (if the engine can take it.) Is you can continue to add fuel till the turbo has released its max flow/efficiency rating. You've just gained substantial hp over a na engine.
You could also consider the smaller engine will consume less fuel until the turbo kicks in and it starts making more power.
You need to remember a diesel is a lean burn engine. The more air you get in it the happier it will be. The larger na engine has to just burn more fuel inefficiently to make the same power.
 

Marlon

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Equipment
Kubota MX5200HST
May 7, 2022
14
2
3
Australia
Really good conversation and thanks all.

First thing to stand out is that I obviously have to get rid of the HST for this type of work.

Then in these responses, I’m still in awe of the various discussions that keep arising around Turbo Engines. While you guys in USA have many more models than us here in Australia, to go from my current TURBO HST to direct drive still with TURBO, I have to jump from a tractor that is
  • 49HP
  • Displacement 2500 (2.5L)
  • Tractor weight 1800kg
  • Turning radius (w/ brake) 2.7m
To a tractor that is
  • 85HP
  • Displacement 3800 (3.8L)
  • Tractor weight 2500kg
  • Turning radius (w/o brake) 4.2m
which I think is too big a tractor for me, loses significant utility capacity, and its power capacity is obviously way over my needs and if the turbo only cuts in when demanded, it may not be required to the extent the turbo is required in my current 49 HP HST so it’s a waste of money jumping to that model just because it has a turbo.

There are two models in between that are Naturally aspirated and are
  • 62HP or 68HP
  • Displacement 3300cc (3.3L)
  • Tractor weight 2180kg
  • Turning radius (w/o brake) 3.6m
Now the discussions on Turbo seem to say to me that the reason my HST can do the job is because of the extra power provided by the Turbo and you are all saying that will use more air and fuel as it cuts in as opposed to when the power is not called for, but that work is work and a non turbo will only use less fuel if it does less work or does the work more easily but that even then it is debateable if it’ll be significant, but surely doing the work stressing the tractor to it’s limits will use more fuel than doing the work easily, even if the tractor uses a bit more fuel just moving itself around between these heavy jobs

So my immediate question is why does a quality manufacturer like Kubota offer so many models where the difference between them as you go up the range is often only small like the above going from 62 to 68 HP, why invest in the manufacturing overheads of producing both these models to gain 6 HP if everything else is equal?

There must be very specific audiences for the individual models in the range which I don’t understand and so how do I pick which audience I am in and therefore which model I should buy to replace my HST?

I’m led to understand that the only difference between the 62HP model and the 68HP model is only bigger injectors which I interpret to mean more fuel at all times and workloads for the 68HP as opposed to the 62HP, therefore I’m wondering if the 68HP isn’t more suited where the majority of the hours are slashing as opposed to utility work and the reason for the existence of the 62HP model is for predominantly utility workloads?

Finally in going to a direct drive, I personally want hydro shuttle to maintain some utility useability that was the reason for getting the HST in the first place before the different work requirements arose, and this combined with the lower tractor weights are why I have moved away from considering the Case JXM range and the JD models, being the only other brands with local service / dealerships.

I don’t know what OP means (here its means over proof when describing rum) but considering all the above, this OP is now trying to decide whether to go from my MX5200 HST to the M6040 or M7040 which are the only M Series models available under 85HP in Australia and are both Naturally aspirated.

Anyone there want to make the decision for me?
 

PoTreeBoy

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Then why have the turbo charger on the diesel to begin with? If the excess air pushed into the engine is of no use?

Honest question.

Seems logical to me that the extra air is needed for something. If not needed for combustion of extra fuel in a diesel, what is its purpose? How would a turbo charger increase HP output otherwise?
The extra air is needed to produce full power. But most of the time we don't need full power, so less fuel is injected creating a lean condition.

The larger, natural aspirated engine always pumps the same amount of excess air at a given speed, regardless of load. But the turbocharged engine will pump somewhat less excess air at reduced load, even without changing the rpm. This is because at light load, lean mixture, the exhaust temperature is lower, and therefore the energy in the exhaust available to spin the turbocharger's turbine is less.

Sometimes, extra air is used for emission control. The extra air helps ensure that a rich condition that produces soot (and other pollutants?) isn't reached.
 

jimh406

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Kubota makes a lot of different models that are very similar because other manufacturers do.
 

PoTreeBoy

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Really good conversation and thanks all.

First thing to stand out is that I obviously have to get rid of the HST for this type of work.

Then in these responses, I’m still in awe of the various discussions that keep arising around Turbo Engines. While you guys in USA have many more models than us here in Australia, to go from my current TURBO HST to direct drive still with TURBO, I have to jump from a tractor that is
  • 49HP
  • Displacement 2500 (2.5L)
  • Tractor weight 1800kg
  • Turning radius (w/ brake) 2.7m
To a tractor that is
  • 85HP
  • Displacement 3800 (3.8L)
  • Tractor weight 2500kg
  • Turning radius (w/o brake) 4.2m
which I think is too big a tractor for me, loses significant utility capacity, and its power capacity is obviously way over my needs and if the turbo only cuts in when demanded, it may not be required to the extent the turbo is required in my current 49 HP HST so it’s a waste of money jumping to that model just because it has a turbo.

There are two models in between that are Naturally aspirated and are
  • 62HP or 68HP
  • Displacement 3300cc (3.3L)
  • Tractor weight 2180kg
  • Turning radius (w/o brake) 3.6m
Now the discussions on Turbo seem to say to me that the reason my HST can do the job is because of the extra power provided by the Turbo and you are all saying that will use more air and fuel as it cuts in as opposed to when the power is not called for, but that work is work and a non turbo will only use less fuel if it does less work or does the work more easily but that even then it is debateable if it’ll be significant, but surely doing the work stressing the tractor to it’s limits will use more fuel than doing the work easily, even if the tractor uses a bit more fuel just moving itself around between these heavy jobs

So my immediate question is why does a quality manufacturer like Kubota offer so many models where the difference between them as you go up the range is often only small like the above going from 62 to 68 HP, why invest in the manufacturing overheads of producing both these models to gain 6 HP if everything else is equal?

There must be very specific audiences for the individual models in the range which I don’t understand and so how do I pick which audience I am in and therefore which model I should buy to replace my HST?

I’m led to understand that the only difference between the 62HP model and the 68HP model is only bigger injectors which I interpret to mean more fuel at all times and workloads for the 68HP as opposed to the 62HP, therefore I’m wondering if the 68HP isn’t more suited where the majority of the hours are slashing as opposed to utility work and the reason for the existence of the 62HP model is for predominantly utility workloads?

Finally in going to a direct drive, I personally want hydro shuttle to maintain some utility useability that was the reason for getting the HST in the first place before the different work requirements arose, and this combined with the lower tractor weights are why I have moved away from considering the Case JXM range and the JD models, being the only other brands with local service / dealerships.

I don’t know what OP means (here its means over proof when describing rum) but considering all the above, this OP is now trying to decide whether to go from my MX5200 HST to the M6040 or M7040 which are the only M Series models available under 85HP in Australia and are both Naturally aspirated.

Anyone there want to make the decision for me?
In reverse order - I flipped a coin and . . . it landed on edge.

OP stands for original poster. That be you.

Interestingly, the difference between the US 6040 and 7040 includes a turbocharger. Maybe the US pollution regs were stricter, requiring the turbo.

I agree with you regarding the array of models.

Finally, I still can't grasp your operation. Mowing 80 to 90 acres with a 6' cutter seems painful. Unless you have a lot of obstacles, then double ouch. I've used a ~47 hp Ford with a 6' cutter and an M7040 with a 7' cutter - both in southern US pasture clipping - and both handled it effortlessly at a ground speed of 4 to 6 mph. And I've seen an M7060 run a 12' batwing through thick grass as tall as the rear tires, although creeping. I have no doubt that combination could mow those pastures at 5 or 6 mph.
 

Dieseldonato

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Reading material.





Your focus should be on matching the size and power output of the tractor to the job at hand. You keep getting hung up of fuel efficiency and we've been over many many many times now, the bigger tractor is just gonna burn more fuel. The hydro is gonna make it burn more fuel, and you don't really need the bigger tractor. For the small mower you currently have. If you go to a larger (I think it was a 12 foot) mower your going to want the extra hp.
Ergo, get the biggest tractor you can afford, that will suit your current needs and possible future needs.
Heck moat any dealer will let you demo a tractor or refer you to a local guy that has the same model tractor to go and look at it and most will let you come over and check them out.
 
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Marlon

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Kubota MX5200HST
May 7, 2022
14
2
3
Australia
So to explain my needs in detail since comments keep coming back to it, I have a Howard NUG180 slasher, don't know if this is a global company or model, but it is just a 6'slasher on skids and got it when I didn't have the current need, saw me as cleaning up the poorly grazed paddocks once or twice, and then maintained by rotational grazing.

Was working fine, but then we had a really extremely wet season which went on for ages, and with that the whole district got infested with shit weeds including Rat Tail grass, Chillian Needle grass, neither of which can be effectively attacked with a weed wiper, have billions of seeds, flow in the water, stick to anything including cattle, machinery etc, and get transported on the wind to an extent as well. Will never get rid of it, the only chemical strategy involves products containing flupropanate and once applied the paddock is out of action for 4-6 months.

Ongoing, these grasses have a a tall thin and tough seed stem up to a meter tall with seed heads at the top, and once slashed off, grow back in about three weeks, so as well as the chemical boom spray initially, there will be regular ongoing mowing on a regular basis as I rotate cattle out, to get the seed stems before the seeds mature.

For this exercise, I see TIME savings in getting a BW12 (cut twice as wide, take half as long), although I'm currently thinking of the Land Pride RC2512 because it has a higher tip speed, and while these flex wing cutters say they only need 40-50HP, I'll bet they'll need more if only for the terrain even though I am really going to be doing a topping job. Either the M6040 or the M7040 will do what I am doing now with theNUG180 slasher, so the real issue is what is the minimum to work either the Land Pride RC2510 (requires 40HP PTO), or the RhinoAG TS12 (requires 50HP PTO)

The reason for the focus on fuel consumption is because no matter what everyone is saying, I know the MX5200 is guzzling way too much fuel, so it is stressed doing the job with the NUG180 on sleds. I could put wheels on that, but I'd still be out there twice as long as with a flex wing and it would still have the heating issues thanks to the HST technology.

The difference between the flex wings and the NUG180 slasher is the NUG is 3PL mounted whereas the flex wings are towed. Given I'll rarely if ever be using the RC2512 in thick, I would have thought the M6040 would be enough, but admit I can't really think of a good reason other than extra purchase price and fuel costs ongoing, to not step up to the M7040
 

mikester

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A paper spec is a paper spec. Park your butt in each machine. Use them for a while. Test all the functions you need to use ie. I won't buy a loader tractor that can't do two functions simultaneously.

See if you can get a demo of each machine to use over a weekend. See how much fuel each one consumes. How comfortable is the operator station - remember you will spend thousands of hours in that seat. Cheap out now and pay for it later.
 
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