Tractor classification — HP vs torque

[S854]

Why do manufacturers rate their tractors according to HP rather than torque?

I can see why automakers use HP ratings to sell their cars… to the uninitiate, HP is king — more HP = faster car… (although this isn’t always the case).

Tractors, on the other hand, make better use of torque… maybe I misstated that, torque is better applied using large, lugged tractor tires.

In my compact tractor world, the under 25 HP class, engine displacement varies greatly… and generally speaking, more cubic inches can result in more torque at a lower RPM… everything else being equal… (I.e. bore, stroke, naturally aspirated etc.)

Comparing apples to oranges, JD 25 HP (1.1 liter) to Kioti 25 HP (1.6 liter), it would seem the larger engine would produce a more useable torque curve starting at a lower, more fuel efficient RPM. i realize HP and torque are related, you can’t have one without the other.

I’ve searched forthis information on manufacturers websites… all they list is HP… why wouldn’t a tractor company want to exploit the torque differences between competing brands?

 

[IndyIan]

Lugability was a real thing in geared field tractors for ground engagement as its a measure of how torque builds as rpm drops so the tractor wouldn't stall out, and since you can't downshift nicely under load, a tractor would just gut it out at lower rpm until it climbed the hill or got through that heavy patch.
With little HST tractors usually running at a constant rpm and not doing much ground engagement where you max out the hp and rpm starts to fall, lugability isn't really too important most of the time?
I guess for mowing perhaps or snowblowing, if you are using cruise control, higher lugability would be nice. I like the HST without cruise and just back off the pedal a bit if the injector pump is going near WO. In low range, I find at 2100rpm+ it doesn't lug too often when pulling the box blade.

 

[Rdrcr]

I agree.

I don’t have the answer. You’re right that you can’t compare 25 HP tractor ratings without digging deeper as you rightly mentioned, displacement and torque very greatly from manufacture to manufacture and engine to engine.

I have no clue why tractor manufacturers use HP for the ratings but, HP is definitely a more familiar term and, I guess you could say HP sells.

Mike

 

[Hay Dude]

Some do give torque specs. Look on tractor data. I don’t really bother much with engine HP.
What you really want to look at for a measure of power is drawbar HP or drawbar performance.

 

[Chewwy]

Why do manufacturers rate their tractors according to HP rather than torque?

I can see why automakers use HP ratings to sell their cars… to the uninitiate, HP is king — more HP = faster car… (although this isn’t always the case).

Tractors, on the other hand, make better use of torque… maybe I misstated that, torque is better applied using large, lugged tractor tires.

In my compact tractor world, the under 25 HP class, engine displacement varies greatly… and generally speaking, more cubic inches can result in more torque at a lower RPM… everything else being equal… (I.e. bore, stroke, naturally aspirated etc.)

Comparing apples to oranges, JD 25 HP (1.1 liter) to Kioti 25 HP (1.6 liter), it would seem the larger engine would produce a more useable torque curve starting at a lower, more fuel efficient RPM. i realize HP and torque are related, you can’t have one without the other.

I’ve searched forthis information on manufacturers websites… all they list is HP… why wouldn’t a tractor company want to exploit the torque differences between competing brands?

Torque to the wheels is what matters, not the torque provided by the engine. Torque provided by the engine can be, and is, multipled or divided by the transmission and rear end gear ratios. The HP provide by the engine cannot be increased.

Torque determines what you can do. HP determines how fast you can do it.

 

[S854]

Torque determines what you can do. HP determines how fast you can do it.

I've seen several BIG tractors working fields around our small "estate"... pulling two or three implements behind them...

Without exception, they were motoring along at a snails pace (compared to the speed they run on the local roads, between fields)...

Which reinforces my question of torque vs HP... those big tractors were relying on the engines torque to get things done... which is why I purchased a tractor in the first place... to get things done...

 

[S854]

These four tractors are from the "25 HP" class... obviously of different physical size... Model and engine size I listed in RED... all the specs (rated HP, rated RPM) came from TractorData

Again, I don't get why Kubota doesn't tout their torque figures...

 

[oldnslo]

I've seen several BIG tractors working fields around our small "estate"... pulling two or three implements behind them...

Without exception, they were motoring along at a snails pace (compared to the speed they run on the local roads, between fields)...

Which reinforces my question of torque vs HP... those big tractors were relying on the engines torque to get things done... which is why I purchased a tractor in the first place... to get things done...

Most tillage and seeding implements are designed to work in the 5 to 6 MPH range which is they are going slow in the field vs down the road. If in rocky soil may be going even slower to reduce impact force on the implement.

 

[zzvyb6]

I'd say horsepower is more important for farming. Torque is the rate of change of horsepower. So, in a car, higher torque gets you a better 0-60 time. Horsepower establishes your top speed. For the same horsepower at the max speed, the higher torque gets you there faster. (Not the best analogy, but keeps it simple. Power is work rate, so how much can you do per second, minute, hour, ...

For farming or tractor apps, power is how wide a mower deck can you handle or how much plow can you pull. Torque would be how quickly can you recover from a plugged up deck or how long will it take to spin up the chipper when you choke it.

Since the best fuel 'economy' usually occurs at the peak torque rpm, (Best breathing and exhausting flow), choosing motor specs to suit you application could save you some $ in the long run.

 

[finn1]

Why do manufacturers rate their tractors according to HP rather than torque?

I can see why automakers use HP ratings to sell their cars… to the uninitiate, HP is king — more HP = faster car… (although this isn’t always the case).

Tractors, on the other hand, make better use of torque… maybe I misstated that, torque is better applied using large, lugged tractor tires.

In my compact tractor world, the under 25 HP class, engine displacement varies greatly… and generally speaking, more cubic inches can result in more torque at a lower RPM… everything else being equal… (I.e. bore, stroke, naturally aspirated etc.)

Comparing apples to oranges, JD 25 HP (1.1 liter) to Kioti 25 HP (1.6 liter), it would seem the larger engine would produce a more useable torque curve starting at a lower, more fuel efficient RPM. i realize HP and torque are related, you can’t have one without the other.

I’ve searched forthis information on manufacturers websites… all they list is HP… why wouldn’t a tractor company want to exploit the torque differences between competing brands?

Look up Daedong engines in your browser. It has all the different engine models, power, peak torque, and emission levels for the Kioti engines.

Looks like includes engines for other applications, too, with, for example, higher rated eng speeds.

The interesting thing to me is the major torque upgrade going from what I think is the CK2610 engine (IDI) to the direct injected 3510/4010 engine. Torque almost doubles.

Also, the 35 hp 3510 engine seems to have the same torque output as the 40hp 4010. Makes sense, since, being a naturally aspirated engine, torque is probably smoke limited.