Why are tractors so under-powered?

[IH782]

Modern diesel engines have come a long way in a short time. The Big 3 have diesels engines that are starting to push triple digits in torque straight from the factory. But meanwhile we are left with engines that are VERY, VERY low on the HP and Torque range for their size. Take for instance the engine in the Mahindra 2555, it is a 2.6L, Common Rail, High Pressure, Direct Injection, Turbo Charged, Intercooled diesel with its own dedicated OBDII ECU just like the diesel engines the big 3 use. The 2.6L, as with its automotive cousins, can vary injection timing, pulse width and number of injections per stroke. If the 2.6L in the Mahindra 2555 were in an automotive application, based on the averages from the Big 3, it would produce 153 HP and 315 ft/lbs of torque. With nothing more than a software flash you could triple you HP and Tq numbers. So why are manufacturers not using the technology, they are incorporating, in their engines to its fullest extent?

Here is a very rough chart I put together to compare the Big 3 with a Kubota 2650 and the Mahindra 2555.

Engine Size HP Tq HP per L Tq per L
_____________________________
Cummins 6.7L 350 800 52 119
Duramax 6.6L 397 765 60 116
Powerstroke 6.7L 440 860 65 128
Mahindra 2555 2.6L 55 113* 21 43*
Kubota 2650 1.3L 26 53* 20 41*

*Calculated


Torque as a % of horsepower: 105%
Average horsepower per Liter: 59
Average ft/lbs of torque per Liter: 121

 

[WilliamBos]

You cannot compare the two. Tractors are geared much lower, so you can get more done more efficiently with lower hp & torque.

The duramax now puts out 440hp/910 foot pounds.

 

[IH782]

You cannot compare the two. Tractors are geared much lower, so you can get more done more efficiently with lower hp & torque.

The duramax now puts out 440hp/910 foot pounds.

Thanks for the update.

 

[CalG]

What difference does it make?

You may purchase a tractor from any range of power you may require. And then add weight to meet your traction demands.

There is NO REASON to extract more raw horsepower from any power plant. The purpose of the tractor is to get the job done. The present arrangements seem to fill the requirement only too well. i.e. there are an over abundance of choices at reasonable cost.

ETA The 1952 modle year Fordson E27n is rated at 25 horsepower.
I want to tell you that my 300 HP four wheel drive sedan (Audi A8) will not out work or out pull those few "old timey" ponys. But I also don't ask the Fordson to send me down the highway at 70mph in comfort.

So ...different horses for different courses.

 

[IH782]

What difference does it make?

You may purchase a tractor from any range of power you may require. And then add weight to meet your traction demands.

There is NO REASON to extract more raw horsepower from any power plant. The purpose of the tractor is to get the job done. The present arrangements seem to fill the requirement only too well. i.e. there are an over abundance of choices at reasonable cost.

Their are many reasons to "extract" more power. From being able to do tasks at a lower RPM to being able to maintain speed on a grade to running implements more efficiently.

 

[CalG]

You are equating the wrong things.

Pick a tractor based on rated HORSEPOWER,

No one buys a tractor based on engine displacement.

WTF are you going to do with a tractor that outputs 300 HP and weighs 2000#?
Spin the wheels?

 

[IH782]

You are equating the wrong things.

Pick a tractor based on rated HORSEPOWER,

No one buys a tractor based on engine displacement.

WTF are you going to do with a tractor that outputs 300 HP and weighs 2000#?
Spin the wheels?

Never said people buy based on displacement, I am simply trying to show that with the technology available more HP and Tq are easily achievable.

Yes, if I had a 2000 lb, 300hp tractor I'd do burnouts any and everywhere I could.

 

[CalG]

You know that the majority of traction engine users favor efficiency above all.

If I can work a field all day on a tank of fuel at a rated 60hp, that means much more to me than working the same field using two tanks of fuel while boasting of 100HP.

But, I agree, burnouts are fun when money is not the issue.
Play on....

 

[MinnesotaEric]

Why are tractors lower power for their engine displacement?

I imagine because they are low revving engines that sip fuel.

And because the rest of the drivetrain would need to become significantly tougher to handle the additional power.

 

[pmsmechanic]

Big three rate their trucks at maximum horse power while tractor manufacturers rate their tractors at continuous horsepower. There is a big difference. None of the big three motors would last a day at maximum hp while your tractor will run all day at continuous hp, then... get up the next morning and do it again.

A top fuel dragster can put out 6-7000 hp for 3-4 seconds. It needs to be rebuilt after a few runs.

A 391 Ford hopped up puts out 5-600 hp. Factory stock would have been about 200. Continuous duty on a pumping unit for irrigation they were rated at 80 hp.

A 5.9 Cummins in a truck sled puller is putting out about 5000 hp. In a truck they hit about 250 -300. I don't remember exactly. In a Versatile tractor they were rated at 150 hp.

 

[pmsmechanic]

The infamous double post strikes again.

 

[paulfun9]

Never said people buy based on displacement, I am simply trying to show that with the technology available more HP and Tq are easily achievable.

Yes, if I had a 2000 lb, 300hp tractor I'd do burnouts any and everywhere I could.

WHy would one want to replace tires on their tractor that often?

 

[stuckmotor]

New 85hp John Deere diesel vs. 18's steam tractor rated @ 18hp. | PowerNation

 

[sixdogs]

With the unneeded extra HP I could mow my lawn and use 17 gallons of fuel rather than 1.2 gallons.

 

[2ndhalf]

With the unneeded extra HP I could mow my lawn and use 17 gallons of fuel rather than 1.2 gallons.

Or 5 gallons of water and a few chunks of coal... :thumbsup:

 

[sixdogs]

Or 5 gallons of water and a few chunks of coal... :thumbsup:

...and six foot deep ruts in the lawn.


My father-in-law actually ran a steam tractor as a boy and said they were geared so low it took forever to go just a short distance. They used to hire kids--like him--to drive the beast from field to field.

 

[JFoy]

Guy that cleared our land recently did so with a big track loader. I asked him the specs of his machine and he said 26,000 lbs and 90 HP. I stood there stunned for a moment when I heard 90 HP. I said, "How can that possibly be with 90 HP?". He said people don't understand that it is weight and hydraulic speed that get the work done. Obviously the frame is substantially heavier. This was a real eye opener for me.

 

[motownbrowne]

Pmsmechanic got it right. It's about duty cycle. You can run a tractor at full power at WOT all day long. That's what they're made for. You'd better not try running your new diesel pickup at WOT putting out it's full rated HP all day...

On a side note, once tractors get a little long on the tooth, bigger, higher HP models are often very cheap. You can buy a 100-200 HP Case, IH, Versatile, Allis-Chalmers for very cheap around here. If you want a tractor with major HP, buy one of them. Putting 100 HP in a compact is just gonna make it more complex, more expensive to buy, and more expensive to repair.

 

[2ndhalf]

On a side note, once tractors get a little long on the tooth, bigger, higher HP models are often very cheap. You can buy a 100-200 HP Case, IH, Versatile, Allis-Chalmers for very cheap around here. If you want a tractor with major HP, buy one of them. Putting 100 HP in a compact is just gonna make it more complex, more expensive to buy, and more expensive to repair.

I've noticed that a lot of guys own really big tractors with high hours; I'm guessing many bought them used. It makes a lot of sense to buy that way if you are handy with a wrench. You could get a really nice tractor with a couple thousand hours left of life left in it.

 

[hayden]

Pmsmechanic got it right. It's about duty cycle. You can run a tractor at full power at WOT all day long. That's what they're made for. You'd better not try running your new diesel pickup at WOT putting out it's full rated HP all day...

On a side note, once tractors get a little long on the tooth, bigger, higher HP models are often very cheap. You can buy a 100-200 HP Case, IH, Versatile, Allis-Chalmers for very cheap around here. If you want a tractor with major HP, buy one of them. Putting 100 HP in a compact is just gonna make it more complex, more expensive to buy, and more expensive to repair.

This and the original pmsmechanic post are why the HP per liter of displacement is much lower in a tractor than in a car. The same thing happens in boats. The same Cummins engine used in Dodge trucks is rated below 200 hp for continuous duty marine use, or pump use, or generator use. Take that same engine and rate it for "pleasure boat" use, and the HP rating jumps up over 300hp. But you can only run it for 1 hr at full power, then need to scale way back. And there are annual limits on the number of hours.

My boat's engine in 9 liters, so nearly double the displacement of the Cummins truck engine, yet is rated at just under 300hp for continuous duty. So it will run at wide open throttle 24x7, pausing only for oil changes, and do so for 20,000-30,000 hours. And the engine, by the way, is a Deere used in large tractors, construction equipment, generator plants, and pumping stations.