Tractor classification — HP vs torque

[LD1]

There would be a performance difference when it comes time to actually do the work. Given proportional sized cooling systems, the larger displacement engine should run cooler. Heat kills engines and bolted-on engine components.
So when the rubber hits the road (or the plow gets dropped into the soil, the bush hog gets pulled through heavy brush) the bigger displacement engine will run cooler and last longer. You can work it harder in the field.

Some things cannot be explained with paper statistics. They just are a certain way a tractor feels when you drive it. In a tractor, I would prefer noticeably more displacement of a bigger engine over a smaller displacement engine, even if the smaller engine had a little more power.

I’m skeptical of these smaller 4-liter-ish, 4 cylinder engines I’m seeing in 100-150HP tractors. I don’t think they are going 10,000 hours. I greatly prefer a 6 cylinder over a 4 cylinder, too. The longer crankshaft and 6 smaller holes firing give me more confidence than a short crank and 4 holes firing.

Is it fair to say you dont like the ~5 - 8ish liter 2-cylinders of 6-7 decades ago?

You are questioning the 4-ish liter 4-cylinders......the deere 4.5 is a pretty tried and true engine and runs from 85ish HP up to 135 or 140. And I wouldnt consider a 4.5L small for a 4-cylinder. Probably one of the larger modern ones before they jump to 6+ cylinders?

 

[LouNY]

Yep, I'm doing work and am not looking for a particular peak. A peak hp or torque valve is meaningless when performing work.
Quite often peak hp is quite a ways from peak torque with less torque but more rpm yielding more hp but when an engine starts to get pulled down doing work it is the torque that allows that engine to continue to do the work.

I think it is just because most people are conditioned to think in terms of horsepower. 45 hp is a relatable term to most people while 38 ft lb of torque comes across as an ambiguous figure. Knowing either max torque or max hp is limited in what it tells you. What is really telling is a torque curve (How much torque at various rpms) A long relatively flat curve is ideal in a tractor.

Just an interesting side note: A steam engine develops max torque at 0 RPM

I gotta go with LouNY on this one. He is holding RPM constant and allowing TORQUE to vary. HP becomes a derivative by definition in the same way that the louder sound created is also a derivative value. Neither sound nor HP are causes. Both are effects, not causes.
rScotty

A smaller faster turning engine can generate more hp and less torque then a slower turning larger engine but the larger engine will do the same work easier and smoother.

 

[Hay Dude]

Is it fair to say you dont like the ~5 - 8ish liter 2-cylinders of 6-7 decades ago?

You are questioning the 4-ish liter 4-cylinders......the deere 4.5 is a pretty tried and true engine and runs from 85ish HP up to 135 or 140. And I wouldnt consider a 4.5L small for a 4-cylinder. Probably one of the larger modern ones before they jump to 6+ cylinders?

I just had 2 Kubotas with 4 cylinder engines and they were 6.1L! Each cylinder is over 1.5L!
I’d prefer a 6 cylinder with 1L per cylinder.

 

[5030]

There is no replacement for displacement

 

[LD1]

As was pointed out earlier in the thread, two 25 HP tractors with two different displacements… seems to me the larger of the engines will generate more torque throughout a broader spread…

This is usually the case....but you know the math and relation of HP and torque now right? Doesnt this ALSO mean the larger engine will make MORE power throughout a boarder spread? Thats what I mean by area UNDER the curve.

Something like a high reving motorcycle engine that winds up to 15000 RPM.....as RPM's drop.....so does HP. half the RPM's may mean only half the HP. But on a engine that makes the same "peak" HP but only spins to 4000rpm......cut the RPM's in half and it may still retain 75% of its power.

IE: flatter HP curve.

Your road tractor can make 1800ft-lbs of torque and lug a 128,000# load up a 6% grade at a road speed right......you think thats torque or power?

With a 3/4" breaker bar and 10' pipe I can also make 1800ft lbs of torque same as your cat engine.
And with a proper apparatus and gearing/mechanical advantage.....under my own human power I could also pull 128,000# up a grade of 6%. BUT.....since I only have about 1/4 HP it would be at a snails pace vs road speed.

 

[LD1]

I just had 2 Kubotas with 4 cylinder engines and they were 6.1L! Each cylinder is over 1.5L!
I’d prefer a 6 cylinder with 1L per cylinder.

Definitely smoother with more but smaller cylinders. But then we get into higher reving vs slightly slower reving engine and start down this torque debate as to which one is better and which one will "lug" better or pull more, etc etc

 

[Hay Dude]

Definitely smoother with more but smaller cylinders. But then we get into higher reving vs slightly slower reving engine and start down this torque debate as to which one is better and which one will "lug" better or pull more, etc etc

The thing in the 4 cylinder’s favor is they are cheaper/simpler to manufacture and cheaper to rebuild.

In farming, 6 cylinder tractors are sought after, as are larger displacement engines. Farmers have their reasons and they are pretty good reasons.

CHN dropped a few of their 6 cylinder engines back about 10 years ago and replaced them with smaller “more efficient” 4 cylinder engines. If you try to buy one of these vintage tractors, many times the seller will advertise that it is “the 6 cylinder version”, because it is preferred by most and brings higher value.

 

[Hay Dude]

Definitely smoother with more but smaller cylinders. But then we get into higher reving vs slightly slower reving engine and start down this torque debate as to which one is better and which one will "lug" better or pull more, etc etc

I think the longer crank luggs better

 

[S854]

Your road tractor can make 1800ft-lbs of torque and lug a 128,000# load up a 6% grade at a road speed right......you think thats torque or power?

Well… according to the dyno, HP is falling off and torque is rising… yes?

IF my small Kioti, with its larger engine than some of its competitors, had dyno curves like the graph above (it doesn’t, I’m sure)… and I could compare that curve to a smaller engined tractor where the engineers concentrated solely on reaching 25 HP through rpm regardless of what that focus did to its useable torque curve… I’d choose flat torque over HP every time… which goes back to my original question… “why don’t manufacturers tout the real world differences between their tractors and the also-ran?”… instead of lumping everyone together under the 25HP tent…

Seems to me a valid selling point for some tractor makers…

 

[rScotty]

Well… according to the dyno, HP is falling off and torque is rising… yes?

IF my small Kioti, with its larger engine than some of its competitors, had dyno curves like the graph above (it doesn’t, I’m sure)… and I could compare that curve to a smaller engined tractor where the engineers concentrated solely on reaching 25 HP through rpm regardless of what that focus did to its useable torque curve… I’d choose flat torque over HP every time… which goes back to my original question… “why don’t manufacturers tout the real world differences between their tractors and the also-ran?”… instead of lumping everyone together under the 25HP tent…

Seems to me a valid selling point for some tractor makers…

Probably because there is engine torque, PTO torque, and then there is the all-important torque at the back axles. The last one is easy to deal with by downshifting. The others not so much, although multi-speed PTOs help somewhat in the real world of getting work done.

The complexity of this thread is probably an answer to why manufacturers and salespeople avoid touting torque numbers and curves. People who find it important can always look it up. It's not secret, just not obvious.
rScotty