Why are tractors so under-powered?

[DavesTractor]

Some thoughts: Duty cycle is the big deal I think, as many have mentioned. On pickups, like a 3500 Ram with a Cummins and a regular pickup bed you get 385 HP and 900 torque. Order that as a cab and chassis and it drops to 325/750. I think it is the same way with GM and Ford. If they actually think we are going to use the rig hard, they give us less!

As for the comment about the 2565 and 2555 being the same except for 10 HP, that is not the case. The 2565 is 800 lbs heavier, 8" longer and uses heavier axles.

There are however other examples you could use that would illustrate your point. The 1533/1538 are the same tractor except the 1538 has larger tires and a different "tune". The 3540 and 3550 likewise share the same engine, different tune and tires. It just happens to be that the 2555 and 2565 are almost entirely different from one another.

As for re-flashing the ECM and making the 2555 an 85 HP tractor, certainly it would seem with 2.6L that should be achievable (disregarding EPA laws...which I don't recommend) but then would the drivetrain hold up? Would the radiator and AC work if you were actually using all that HP to run a 12' mower through tall grass in the summer? I suspect you would over heat the radiator and then max the head pressure on the AC and have all sorts of issues.

Having said that, I'm a tinkerer and hot rodder at heart. My last fast car had a cam/tune with >600 hp and under 3100 lbs, more than once I transferred a bunch of rubber from my tires to my fender wells. It's nearly irresistible. It makes no sense to turn expensive tires into smoke, but man does it put a grim on a guys face. So I am with you in the concept of "more power" but you probably ought to not tinker with the power on a Tier IV tractor. Get an old 70-80's International and put a turbo on it. Turn it up until it blows or you run out of nerve.

 

[adventure bob]

Even pulling four horses up a huge grade, like highway 24 up to the mountains, my Cummins gets nowhere close to 100% duty cycle. There's not pickup on the planet that will survive 100% duty cycle for long. If you doubt that one and think your pickup can, come see me, we'll get you on a true water brake dyno and Ill destroy your truck in less than 30 minutes.
There's some confusion about HP and duty cycle that a lower HP will live longer. Lower HP only lives longer because the support systems, oil, cooling, fuel, are designed for that output. When the HP goes up those systems have to increase capacity proportionately. This is why guys who just throw tuners on their pickups generally have issues. They've increased the HP, actually they've increased heat and stress loads, without increasing the cooling, fueling and oiling systems. They have failures. It always amazes me when folks think they can get to 700-1000HP with a tuner and a couple of bolt ons, when an industrial injection diesel around a 1000HP is in the $15K range just for a short block. Its due to all the work to increase the duty cycle, stress capacity oiling and cooling to support that output. I could easily, not cheaply mind you, get my current cummins up to 1000Hp and have it do that happily. However it would probably cost me somewhere near $20K so that I had the reliability of a stock engine. Then I would have to drop about $12K in a transmission to handle it and I know that American Axle in the rear wouldn't live long like that, so a new axle around $15K would have to be dropped in. Not to mention all the small parts like driveshafts ect.
So, while our underpowered tractors could crank out more HP cheaply, like the pickup guys like to do, it would cost the manufacturer way more to make sure everything that the HP jump affected could withstand the increase. That's big money and you wouldn't pay for that kind of jump in cost or you wouldn't accept the hit to reliability.
HP cost money, how much can you afford?

 

[ultrarunner]

We had a guy that did dirt track racing back in the day with 40hp Model A engines...

They would raise compression with a bolt on overhead valve conversion and triple or more the Horsepower...

It was a good day when the engine lasted the day...

 

[motownbrowne]

The big 3 Diesel engines run all day every day at maximum hp. There are a lot of people hauling heavy loads with these trucks for 8-10 hours a day. The tractor engines are low hp, but high torque. This is what a tractor need torque. The plus side is the lower the hp the longer the engine lasts. This a bonus for tractors since they last more than 10 years like cars and trucks do. If you look at the hp ratings for like a Ford F650 you notice that it is much lower than the F250 and 350. It is detuned for longer operation.

I'm sorry, but this just isn't correct. Maximum HP means WOT at the redline just barely making enough power to maintain speed. Holding speed, but unable to accelerate.

There are not trucks that do this all day. A diesel in a pickup gets to go down hill fairly often, and even pulling a great load up a grade still isn't at 100%.

You know many truck owners who let their trucks run at the rev limiter all day?

 

[art]

Just like I will argue with engine oils for trucks not being the same as tractors lets look at how they are run. To look at a car which runs at roughly 1/4 throttle and 1/4 load! A over the road truck which runs about 1/3rd throttle and 1/3rd load while going down the road. Tractors run full throttle and full load while doing work! Most home owners don't run there tractors that way which is why there is often questions of reliability on some when put into a normal tractors work vs the part time applications of home owners vs commercial operation where they are often run more in one week then a home owner will run one in a year! The load comparison of any other work other then construction is not going to compare to farm work!!

 

[DK35vince]

A over the road truck which runs about 1/3rd throttle and 1/3rd load while going down the road.

Not sure what trucks are running at 1/3 throttle. Certainly none that I have ever driven could be run at 1/3 throttle and maintain speed loaded.
Example, maintaining interstate speeds of 65-70 MPH, the truck I currently run with a 425 Cat I run at or near full throttle trying to maintain that speed loaded.
All other trucks I have run over several decades were the same, full throttle most of the time.

 

[TomSeller]

Not sure what trucks are running at 1/3 throttle. Certainly none that I have ever driven could be run at 1/3 throttle and maintain speed loaded.
Example, maintaining interstate speeds of 65-70 MPH, the truck I currently run with a 425 Cat I run at or near full throttle trying to maintain that speed loaded.
All other trucks I have run over several decades were the same, full throttle most of the time.

How do they maintain speed then on long grades? Not disagreeing but it seems loaded semis are at the speed limit on hills more often than not. No?

 

[LD1]

I thing OTR trucks (aka semis) could be lumped a little more closely with tractors. And one could also ask "why they are underpowered" as well.

Heck, 14+ liter engines only making aboit 500hp? The big 3 are pushing that with half the displacement.

So what I am saying, the HP per displacement ratio....of semis, is closer to tractors than say, a modern 1-ton diesel truck.

But even so, semis don't see 100% load all day like tractors. Flats and downhills, probably not even close to WOT. Where as a tractor pulling a plow.....even downhill, WOT is where she stays

 

[DK35vince]

How do they maintain speed then on long grades? Not disagreeing but it seems loaded semis are at the speed limit on hills more often than not. No?

If you say so.
Hills, long grades around here semi's struggle to maintain speed limit.
Like I said any truck I've run, I run at or near full throttle a large % of the time to maintain speed limit

 

[RaydaKub]

But even so, semis don't see 100% load all day like tractors. Flats and downhills, probably not even close to WOT.

Tough to know anymore. My nephew drove for a national name a year ago and hit every state in the Lower 48. They had governors on them to limit them to 63 mph or so no matter what road they were on. You'd never know whether the throttle was wide open or not.

 

[redshirt]

Please go tell Kenworth, Petebilt, Freighterliner, Volvo, that their doing it all wrong, their trucks won't run 5,000 to 6,000 miles a week in a team situation. I think they will tell you they can, will, and have done it for years.

 

[LD1]

Please go tell Kenworth, Petebilt, Freighterliner, Volvo, that their doing it all wrong, their trucks won't run 5,000 to 6,000 miles a week in a team situation. I think they will tell you they can, will, and have done it for years.

Maybe I missed it somewhere......but I didnt see anybody make the claim that they are doing it wrong

 

[k0ua]

I think that's because the OP already pointed out in the original post that the torque per liter (in addition to hp per liter) is also much lower in tractor applications than pick-up trucks.

- HP / torque characteristics are chosen based on a tractors weight and intended use
- engine is chosen that can reliably deliver HP/torque required by tractors weight and intended use
- Marketers then sell several models with slight bumps up in HP and charge big premiums for them because "everyone wants the best".

Interesting to note, that what is considered over powered vrs underpowered is often debated on TBN. Except people usually call overpowered tractors underweight! It all depends on the application. If you want to mow big fields and run the largest mower possible HP is important. If you want to push over a tree, gearing, weight, and torque are important.

This reminds me of a video I did once. My friend had a Toyota Echo (108hp) and thought it would out pull my 19hp tractor due to the superior hp. No chance. Anyway, watch the video if you'd like. Jeep Rubicon vs 19 hp tractor is also on there. It shows that for many tractor tasks, hp doesn't matter. (but for field work, more hp means more speed less time with same implement - I get that)

Kioti LB1914 vs. Toyota Echo and Jeep Wrangler (Tractor Pulling) - YouTube

And that was pulling against a pretty small tractor. It might be interesting to see what the Ford 250 would do against your DS4510HS. A closer match for sure.

 

[k0ua]

Just in case it's not clear, there are really two different questions being answered here. I actually don't know which the OP meant to ask.

Question 1 is why tractor engines are rated for so much lowered HP per liter of displacement compared to pickup diesels. The answer has to do with duty cycle for the engine in its application.

Question 2 is why don't our tractors have more horsepower than they do. The answer comes down to traction, and the max size implement the tractor can handle and its horsepower requirements.

In my experience snow blowers and field mowers are the only things that really put a load on the tractor engine. For any kind of pushing or pulling the wheels will spin before the engine bogs down. A snow blower is the only thing I've used that can seriously bog down a tractor.

One other application is spinning an electrical generator. You can run out of HP easily there and be wishing for much much more if the generator isn't sized correctly.

 

[Btown]

And that was pulling against a pretty small tractor. It might be interesting to see what the Ford 250 would do against your DS4510HS. A closer match for sure.

The tractor has the advantage in this due to being on dirt. Those tires have better treads than both the car and Jeep. Do this on asphalt and I bet there will be a much different result.

 

[LD1]

My truck is something like 315hp/625 ft lbs and 7900#

My tractor is 51hp and about 1000# lighter.

I like the tractors chances in a tug-of-war on any surface condition including pavement

 

[gladehound]

The tractor has the advantage in this due to being on dirt. Those tires have better treads than both the car and Jeep. Do this on asphalt and I bet there will be a much different result.

hmmm.... let's see - the car did have chains on. But back to the question. What would happen on asphalt.

I predict lot more smoke from the car - tire smoke or transmission smoke, maybe a little of both. Or maybe something on the car would outright break. But one thing is certain, there is no surface on which that ~2000 pound car would out pull a 3800 pound tractor, even if it only has 19hp!

however, I do predict that the Jeep, weighing 600 pounds more and having lockers on both axles would out pull the "3 wheel drive" tractor on asphalt.

 

[gladehound]

And that was pulling against a pretty small tractor. It might be interesting to see what the Ford 250 would do against your DS4510HS. A closer match for sure.

Sold the F250 before getting the DS4510HS. Weight is very similar, close enough that I don't know which is heavier. No doubt the DS4510HS would pull the F250 on any surface. The F250 had a worn out limited slip rear diff which i.e. functioned like an open diff. The front diff also did not lock. The tires on the truck were a harder rubber as well. Don't think the F-250 would have much of a chance.

 

[gladehound]

My truck is something like 315hp/625 ft lbs and 7900#

My tractor is 51hp and about 1000# lighter.

I like the tractors chances in a tug-of-war on any surface condition including pavement

LD1, just noticed the MX in your profile. Nice upgrade! I guess I'm a little late the to party on that one!

 

[LD1]

LD1, just noticed the MX in your profile. Nice upgrade! I guess I'm a little late the to party on that one!

Yea, a little late

Made the upgrade earlier this year in the spring. April or May sometime?