Tractor classification — HP vs torque

[sd455dan]

Thats the difference between the performance of diesels and gas engines. Diesels when loaded drop in rpm but the available torque increases with that drop in rpm. Gas engines just drop in rpm and also drop the available torque.

That is not always true in tractor engines.

I can't find it now but Nebraska tractor tests at one time had both the gas and diesel Ford 3000 engines graphed and the gas had torque number which extended about 150 RPM Lower down to around 800 RPM IIRC

a quote from yesterdays tractors:

If you were to root out the nebraska test results for the Ford 3000 and 5000 tractors in both the gasoline and diesel versions using the 175 cid and 233 cid engines respectively I believe you'll find that they have almost identical curves... much to the point that the profiles are the same excepting that the spark engine will probably achieve peak torque at 100-150 rpm faster than the diesel. This will result in the spark engine being a bit prouder on the top end because the torque rise was basically identical to the diesel. Again... SAME cam shaft in both. Same lift. Same duration. Same stroke and displacement.

Interesting bore / stroke as well being "dead square" engines @ 4.2" x 4.2"

 

[LD1]

Sorry you don’t get it.

Properly geared the 110 hp engine could move the Case just fine, but likely not very fast. Torque can be mutipled via gearing. HP cannot be multiplied by gear ratios.

BINGO

 

[S854]

… Diesels when loaded drop in rpm but the available torque increases with that drop in rpm...

That kinda gets back to my original question…

The guv’ment, in its infinite wisdom, decreed 25 HP was the cutoff for their emissions mandate…

I could create an absurd argument that, if one was to take the CASE steam tractor from the video, scale it down to 25 HP, the torque created by that particular engine would vastly outpace any modern CUT…

Obviously, a manufacturer isn’t gonna create such a monster, but the amount of torque produced by the various range of consumer aimed diesel engines is different… my original question was: Why don’t manufacturers boast about the differences in torque produced by their 25HP engine as opposed to the other manufacturers engines?

 

[Chewwy]

. . . Why don’t manufacturers boast about the differences in torque produced by their 25HP engine as opposed to the other manufacturers engines?

In my opinion, it seems the answer is obvious based on this thread. Most people do not understand torque and its relationship to hp and engine rpm. They are likely comfortable, even if not knowledgable, with hp.

This is likely also true for the marketing folks at the various manufacturers. They too don’t understand or appreciate torque.

 

[LD1]

Because there are MANY MANY more important things to compare when tractor shopping than torque. HP is how fast work can get done. And thats what is important to just about everyone. How fast can I plant a field, how long is it gonna take me to mow my lawn.

How big of a bushhog or tiller to buy is a function of HP and NOT torque.

You can take a 100yr old steam tractor with 110hp and you can take a 110hp modern tractor and do the SAME RATE of work. Sure....given the traction and weight.....you may only be able to pull an implement 1/2 or 1/3 the size......but you can do so at 2x or 3x the speed.....hence the SAME RATE or work being done.

If you want to talk about lower RPM torque.....or what the curve does when an engine starts lugging.....you can ALSO get that data with a HP curve. Also called area under the curve....rather than looking at peak HP.

But when it comes to comparing tractors.....you can shop a deere vs kubota vs Massey vs mahindra vs whatever you want.....as long as you are shopping the same "class" of tractor with equivalent HP.....while there "may" ve some slight variations in engine torque....its not gonna be anything to quarrel about when tractor shopping and they will all be equally capable.

People constantly questioning torque.....or wanting to compare old steam tractors....or those saying things like HP shouldnt be used to rate a tractor and torque is a better number....those people clearly have zero understanding between the relationship between torque and HP.

Torque is nothing more than how much force can be applied. Nothing more, nothing less. HP is nothing but a number comprised of TORQUE with a time element. IE: how fast can you apply said torque.

 

[LouNY]

Till you get to two 25HP tractors, both diesels and one is a 77 cu.in. engine and the other is over 100 cu. in.. No doubt in my mind as to which one is likely to out pull and work the other. Especially if I'm not afraid to turn the fuel screw a bit.

 

[Fuddyduddy1952]

Horsepower is just a mathematical derivative of torque. All hp/torque curves cross at 5252 rpm. I can chain my two 2 cyl. 26 hp zero turn mowers to an old single 14hp Economy Power King which will drag them all over the farm. 52hp vs 14, the two mowers outweigh the Economy.
I pulled my farriers Cummins diesel Dodge 3500 out of a snowy ditch with my 6 cyl F150, 170 hp. Loaded Dodge probably 10,000#, uphill...he forgot left parking brake on. Pulled probably 3 mph, no chains or weight.
Hp= speed, torque pulls in a sense.

 

[Chewwy]

Horsepower is just a mathematical derivative of torque. All hp/torque curves cross at 5252 rpm. I can chain my two 2 cyl. 26 hp zero turn mowers to an old single 14hp Economy Power King which will drag them all over the farm. 52hp vs 14, the two mowers outweigh the Economy.
. . .

One could also say that torque is just a mathematical derivative of horsepower. Horsepower and torque are indeed directly related to each other and the engines speed.

5,252 rpm is the number of revolutions required to make the hp and torque equal numerical values (i.e., X hp and also X ft lbs). 5,252 rpm is not even achievable in most diesel engines.

 

[LD1]

Till you get to two 25HP tractors, both diesels and one is a 77 cu.in. engine and the other is over 100 cu. in.. No doubt in my mind as to which one is likely to out pull and work the other. Especially if I'm not afraid to turn the fuel screw a bit.

Actually.....all else being equal....they will pull and work the same.

But odds are if one is 77cu in and another is over 100 cu in they are probably different size machines.

Put those two engines in the SAME or similar tractors (weight, tire size, traction) and the results will be the same.

 

[LD1]

Horsepower is just a mathematical derivative of torque. All hp/torque curves cross at 5252 rpm. I can chain my two 2 cyl. 26 hp zero turn mowers to an old single 14hp Economy Power King which will drag them all over the farm. 52hp vs 14, the two mowers outweigh the Economy.

Has nothing at all to do with HP or torque. Its all about traction. Both the zero turns can spin the tires while doing so. Just because the powerking can drag them doesnt mean they can work as hard, or have less torque. It simply means they arent designed for pulling something....they have slicks for tires to not tear up your lawn....

But tell me.....which one can pull a 60" mower through tall grass faster without bogging the engine?

You comparison is about as silly as hooking a semi to a 200hp farm tractor.....driving out into the middle of the field and seeing which one will pull the other. The semi obviously has more HP, more torque, and a bigger engine.....so why would it fail to pull a farm tractor around in the field?