why horsepower

[1930]

Why is horsepower so important on a tractor.

On a car or truck for me I am after torque first and horsepower secondary as the vehicle is already launched, torque value is what I would think a tractor would be advertised as cause low rpms engine, stump pulling torque is what we are all after.

So what gives?

Ok I also just have to ask......all that is in my head is all the comments about how the L2501 is severely de-tuned to get under that tier 4 radar gap and because of this its a slug, anyone here experienced with tuning these tractors maybe give some ideas, maybe in the breathing dept or some hotter sticks?

Just curious :thumbsup:

 

[hiddentacocatneddih]

Because the tractor replaced the horse in the field

 

[TheMadOne]

Tractors are marketed by HP because it's an easy number. Most people look for PTO HP, for work done with a PTO driven implement, and weight, for work done with ground engaging equipment. My previous L3301 and current L3560 are vastly different tractors in the ground engaging category, but in theory any PTO implement the L3560 runs the L3301 would handle fine. Manufacturers use engine HP because it's a higher number, and I'm sure some of them like that they can hide "clunkers" with low efficiency between the engine and PTO HP ratings.

That said, the L2501 isn't a slug. It's probably the best balance of HP to weight offered in the standard L. I could, and have on more than one occasion, spun 3 tires with the L3301. It simply doesn't have enough iron, even loaded down with beet juice and a FEL for the tires to grab and pull properly when powered by the higher HP version of the engine. I can only imagine the L3901 is worse.

The L2501's main deficiency is in PTO HP. With only 19 PTO HP on tap you're in a situation of having a 5' wide tractor that really should be paired with 4' PTO implements.

The other issue with the tractor is they de-rated the hydraulic pump. I've never been clear on why. But that leads to reduced flow for any implements and longer cycle times for the loader and backhoe, as well as a negligible drop in pressure, which manifests as slightly reduced capacity on the loader and backhoe.

As far as "turning up" a modern tractor, it's not like the old days. The L2501 uses the same direct injection engine as its bigger brothers. Everything's controlled by the brainbox, and I don't think there's a large enough market to support chipping it.

 

[Citydude]

Tractors are marketed by HP because it's an easy number. Most people look for PTO HP, for work done with a PTO driven implement, and weight, for work done with ground engaging equipment. My previous L3301 and current L3560 are vastly different tractors in the ground engaging category, but in theory any PTO implement the L3560 runs the L3301 would handle fine. Manufacturers use engine HP because it's a higher number, and I'm sure some of them like that they can hide "clunkers" with low efficiency between the engine and PTO HP ratings.

That said, the L2501 isn't a slug. It's probably the best balance of HP to weight offered in the standard L. I could, and have on more than one occasion, spun 3 tires with the L3301. It simply doesn't have enough iron, even loaded down with beet juice and a FEL for the tires to grab and pull properly when powered by the higher HP version of the engine. I can only imagine the L3901 is worse.

The L2501's main deficiency is in PTO HP. With only 19 PTO HP on tap you're in a situation of having a 5' wide tractor that really should be paired with 4' PTO implements.

The other issue with the tractor is they de-rated the hydraulic pump. I've never been clear on why. But that leads to reduced flow for any implements and longer cycle times for the loader and backhoe, as well as a negligible drop in pressure, which manifests as slightly reduced capacity on the loader and backhoe.

As far as "turning up" a modern tractor, it's not like the old days. The L2501 uses the same direct injection engine as its bigger brothers. Everything's controlled by the brainbox, and I don't think there's a large enough market to support chipping it.

As an L2501 owner, your spot on. Aggressive power to the wheels, weak on the PTO.

 

[ruffdog]

You have to use horsepower because that is torque x RPM....the amount of work that can be acheived. When a tractor is hooked to the local PTO dyno, they get 2 numbers. The first one is how hard the tractor is trying to twist the dyno in lbs. The second is at what RPM the highest "twist" happens. Calculating these numbers together give you horsepower. The numbers the manufacturer gets when the engine is on a test stand doesn't mean as much as what it produces out the rear shaft.

 

[Raspy]

Why is horsepower so important on a tractor.

On a car or truck for me I am after torque first and horsepower secondary as the vehicle is already launched, torque value is what I would think a tractor would be advertised as cause low rpms engine, stump pulling torque is what we are all after.

Torque is simply a force that has no movement. RPM only describes speed. Speed at a given torque, combined, is horsepower. Horsepower is what does work. Work is accomplished by rotation that is backed up with torque.

So, if you have a rotating shaft, how fast is it going and how much force is trying to keep it turning?

If you put an arm on the shaft that was one foot long, and it was able to lift a 10 lb weight out at the end of the arm, the force would be 10 ft lbs., or 10 ft lbs of torque required to lift the weight. How fast it lifted the weight, combined with how much weight, would add up to horsepower.

Hi torque engines run slower for a given horsepower. Engines that turn twice as fast, can be geared two-to-one and provide twice as much torque. So a small engine can provide a lot of torque if the power is fed through a transmission to match the engine to the load, as in cars.

However, it's impractical for a tractor engine to be running at 10,000 RPM all the time, and geared way down to a useful RPM to multiply the torque. Just as it's impractical for a chain saw to weight 500 lbs and be geared way up from 1,000 RPM to match the required speed.

Smaller engines can be made to put out a lot of horsepower, but they are harder to control and cool and make last a long time under those conditions. Each machine needs the appropriate sized engine, not just for the horsepower it requires, but for the practicality of carrying that engine around (tractor, car, motorcycle). Stationary generator engines can be heavy, airplane engines must be light. Tractors need weight to engage the ground and remain stable, locomotives need weight and must run a very long time, Chainsaws must be light and powerful, but don't run many hours, etc, etc.

When you see a tractor/trailer rig pulling a grade, it's the horsepower that's doing the work. But the engine is very heavy and slow turning. This means it has high torque and low RPM, for it's rated horsepower, is durable and the transmission can be a simple design to match the engine to the wheels. It makes more sense than having 100 chain saw engines hooked up to the wheels, but the horsepower is the same. And the speed up the grade is the same because it's the horsepower that does the work. Torque is only one part of horsepower.

 

[s219]

Ok I also just have to ask......all that is in my head is all the comments about how the L2501 is severely de-tuned to get under that tier 4 radar gap and because of this its a slug, anyone here experienced with tuning these tractors maybe give some ideas, maybe in the breathing dept or some hotter sticks?

Just curious :thumbsup:

Not sure where you are reading this, because it's well known and acknowledged here on TBN that the L2501 is a sleeper. It has the engine from an older L3400 (34HP) tractor, limited by RPM to max out at ~25HP. Between zero RPM and the RPM limit, it feels like the 34HP tractor. The engine has a lot of guts and torque down low. Most of us use our tractors in that RPM range, so for all practical purposes, it's going to behave like a 34HP tractor for people who have experience with tractors. In my brief time with an L2501, it felt gutsier than my 32HP L3200.

Weight and traction are as important as power on a tractor, for any work that isn't stationary. That's also different than we think about cars or trucks. You need to get it out of your head that tractors are the same as cars and trucks. And for the love of god, go start using your tractor and stop with all the hair-brained posts on TBN.

 

[Raspy]

And for the love of god, go start using your tractor and stop with all the hair-brained posts on TBN.

:laughing:

 

[rangerfredbob]

hp=torque*rpm/5252

Given most tractors run similar engine speed HP is a direct relation to HP, and as everyone said above, horsepower is the amount of work that can be done, the torque measurement depending on the setup of the engine if the torque peak is below the PTO or rated rpm is the capability of the engine to keep up with a surge load like running into a thick chunk of grass or something...

A big part of everything is marketing, a few years ago small engines were switched to being rated on torque but still at 3600rpm, I think they're back at HP rating, same difference, it's more of a "class" of equipment, in the small engine world like lawnmowers and riding mowers not a huge difference either since everything is rated at 3600rpm unless it's diesel where they're rated at 1800-2400rpm usually

And yes, I do know what I'm talking about, I was just tuning and running emissions tests on a 454ci LS based marine engine earlier today making just over 500hp and deal with industrial engines that have peak torque ratings down around 1800rpm where it's needed for the application. Tractor engines are rated for HP at usable engine speeds unlike cars where they are rated at 6000rpm or above when in operation never go over 3500rpm unless shifted manually.

 

[Fallon]

PTO HP is done at the rated 540 RPM. Ends up as the great equalizer as the only difference there is torque.

 

[1930]

Tractors are marketed by HP because it's an easy number. Most people look for PTO HP, for work done with a PTO driven implement, and weight, for work done with ground engaging equipment. My previous L3301 and current L3560 are vastly different tractors in the ground engaging category, but in theory any PTO implement the L3560 runs the L3301 would handle fine. Manufacturers use engine HP because it's a higher number, and I'm sure some of them like that they can hide "clunkers" with low efficiency between the engine and PTO HP ratings.

That said, the L2501 isn't a slug. It's probably the best balance of HP to weight offered in the standard L. I could, and have on more than one occasion, spun 3 tires with the L3301. It simply doesn't have enough iron, even loaded down with beet juice and a FEL for the tires to grab and pull properly when powered by the higher HP version of the engine. I can only imagine the L3901 is worse.

The L2501's main deficiency is in PTO HP. With only 19 PTO HP on tap you're in a situation of having a 5' wide tractor that really should be paired with 4' PTO implements.

The other issue with the tractor is they de-rated the hydraulic pump. I've never been clear on why. But that leads to reduced flow for any implements and longer cycle times for the loader and backhoe, as well as a negligible drop in pressure, which manifests as slightly reduced capacity on the loader and backhoe.

As far as "turning up" a modern tractor, it's not like the old days. The L2501 uses the same direct injection engine as its bigger brothers. Everything's controlled by the brainbox, and I don't think there's a large enough market to support chipping it.

I have only read your response thus far, I'm at the shop, have to start working and will read the others later.

I found your response informative and easy to understand, I'm short on time right now, I'll make a better response later on this evening but I'd like to mention that I thought the l2501 was not computer managed therefore wouldn't need a chip to enhance performance. Thanks

 

[oosik]

For me it's all about weight. I could gear my previous tractor down and spin all four wheels - same with my new M6040. However, the added weight of my M6040 ( 10,100# ) means extra "grunt" before the four wheels start spinning.

Bigger tractor, more weight, more grunt, larger implements = larger projects.

 

[1930]

Tractors are marketed by HP because it's an easy number. Most people look for PTO HP, for work done with a PTO driven implement, and weight, for work done with ground engaging equipment. My previous L3301 and current L3560 are vastly different tractors in the ground engaging category, but in theory any PTO implement the L3560 runs the L3301 would handle fine. Manufacturers use engine HP because it's a higher number, and I'm sure some of them like that they can hide "clunkers" with low efficiency between the engine and PTO HP ratings.

That said, the L2501 isn't a slug. It's probably the best balance of HP to weight offered in the standard L. I could, and have on more than one occasion, spun 3 tires with the L3301. It simply doesn't have enough iron, even loaded down with beet juice and a FEL for the tires to grab and pull properly when powered by the higher HP version of the engine. I can only imagine the L3901 is worse.

The L2501's main deficiency is in PTO HP. With only 19 PTO HP on tap you're in a situation of having a 5' wide tractor that really should be paired with 4' PTO implements.

The other issue with the tractor is they de-rated the hydraulic pump. I've never been clear on why. But that leads to reduced flow for any implements and longer cycle times for the loader and backhoe, as well as a negligible drop in pressure, which manifests as slightly reduced capacity on the loader and backhoe.

As far as "turning up" a modern tractor, it's not like the old days. The L2501 uses the same direct injection engine as its bigger brothers. Everything's controlled by the brainbox, and I don't think there's a large enough market to support chipping it.

Bearing in mind I know almost nothing about PTO engineering ( as far as I know at this point it's nothing more than another output shaft on the trans. ) couldn't the user change gears within the 2501 to change the speed of the output shaft to their desires (assuming the gears we're avail. ) and if so why wouldn't Kubota have made it more efficient in the first place?


On the pump ( and again know even less about the pump) couldn't the user replace the pump with a more efficient unit or wordy case bore/sleeve their existing pump and match with a larger piston to increase volume?

I already commented on the brainbox above.

I'd like to hear whatever you can tell me about the things we have discussed above. Thanks

 

[1930]

For me it's all about weight. I could gear my previous tractor down and spin all four wheels - same with my new M6040. However, the added weight of my M6040 ( 10,100# ) means extra "grunt" before the four wheels start spinning.

Bigger tractor, more weight, more grunt, larger implements = larger projects.

I have some pict. thoughts to share with you once I get home to my desktop.

 

[1930]

Thanks for the other comments, food for the brain

 

[Zebrafive]

Bearing in mind I know almost nothing about PTO engineering ( as far as I know at this point it's nothing more than another output shaft on the trans. ) couldn't the user change gears within the 2501 to change the speed of the output shaft to their desires (assuming the gears we're avail. ) and if so why wouldn't Kubota have made it more efficient in the first place?


On the pump ( and again know even less about the pump) couldn't the user replace the pump with a more efficient unit or wordy case bore/sleeve their existing pump and match with a larger piston to increase volume?

I already commented on the brainbox above.

I'd like to hear whatever you can tell me about the things we have discussed above. Thanks

PTO rpm is standardized at 540rpm or 1000rpm. Implements are designed with this in mind. Manufactures can design what engine rpm is required to produce the correct PTO rpm. It's normally at peak engine HP.

 

[Egon]

Anyone recall drawbar horsepower?? It was delegated to the pulling capabilities.

 

[TheMadOne]

Bearing in mind I know almost nothing about PTO engineering ( as far as I know at this point it's nothing more than another output shaft on the trans. ) couldn't the user change gears within the 2501 to change the speed of the output shaft to their desires (assuming the gears we're avail. ) and if so why wouldn't Kubota have made it more efficient in the first place?


On the pump ( and again know even less about the pump) couldn't the user replace the pump with a more efficient unit or wordy case bore/sleeve their existing pump and match with a larger piston to increase volume?

I already commented on the brainbox above.

I'd like to hear whatever you can tell me about the things we have discussed above. Thanks

The PTO goes 540 RPM. That's it. That's all you get. That's what implements are designed to handle. You can over/under speed it, but the designed setup is what everything should be sized by. (Torque X RPM)/5252=HP. If we know RPM is 540 then it's a simple enough calculation to get HP based on how much actual force the engine turns the shaft with, PTO HP is calculated at the peak of the Torque curve of the engine. As speed is constant then there is no "changing gears". The exception to this is 540E PTO mode that some tractors have. This actually reduces available PTO HP by moving the point that the drive system provides 540RPM off the peak of the torque curve.

As for the pump, it's buried inside the tractor, and not user serviceable. It also controls the steering and the brakes. Unless you really know your stuff, any "upgrades" you make are a good way to void your warranty and end up with an expensive lawn ornament.

 

[1930]

The PTO goes 540 RPM. That's it. That's all you get. That's what implements are designed to handle. You can over/under speed it, but the designed setup is what everything should be sized by. (Torque X RPM)/5252=HP. If we know RPM is 540 then it's a simple enough calculation to get HP based on how much actual force the engine turns the shaft with, PTO HP is calculated at the peak of the Torque curve of the engine. As speed is constant then there is no "changing gears". The exception to this is 540E PTO mode that some tractors have. This actually reduces available PTO HP by moving the point that the drive system provides 540RPM off the peak of the torque curve.

As for the pump, it's buried inside the tractor, and not user serviceable. It also controls the steering and the brakes. Unless you really know your stuff, any "upgrades" you make are a good way to void your warranty and end up with an expensive lawn ornament.

Great answer and more to think about once my warranty vexpires and assuming I see a problem.

All I see is improve torque curve

 

[MossRoad]

Anyone recall drawbar horsepower?? It was delegated to the pulling capabilities.

Yes. The topic is rarely discussed here.