Why are tractors so under-powered?

[Redlands Okie]

Kioti LB1914 vs. Toyota Echo and Jeep Wrangler (Tractor Pulling) - YouTube[/QUOTE]

The guy standing behind the tree and filming must have seen straps, tow ropes, hooks or such break before

Good thinking

 

[AGRIMAN]

Re: Why are tractors so under-powered

I see stuff like this on Power Block TV, they take a 4 cylinder out of a Ford Ranger and put a big V8 back in, why so they can spin tires in high gear and go like a bat out of heaven...

Easy now.... There are many good reasons for putting a big V8 in Ford Rangers. In my case, it's to make it skip across the top of the mud. Whatever your reason, learning to put the power to the ground is just part of it.

97 Ranger with a 557ci BBF.

 

[woodlandfarms]

Uhm. 650HP

Largest John Deere Tractor to Hit the Marketplace | Agweb.com

 

[motownbrowne]

Uhm. 650HP

Largest John Deere Tractor to Hit the Marketplace | Agweb.com

Mmmmmm, 15 liter Cummins. Sign me up!

 

[LD1]

Let me give it a shot here, and I am sure I am gonna repeat alot of what has been said. PMSmechanics post at the end of page 1 is spot on.

First: To answer the "Why need more power" question.........alot of tasks with a tractor, traction ISNT the limiting factor. HP is. My 50HP tractor is physically big enough to pull a 15' batwing or bigger. Do I have the HP to run it....NO. Anyone who has bogged down a rotary cutter because they hit a dense patch in too high of a gear....understand what I am talking about. ANYTHING driven off the PTO could stand for some more HP. An average 3000# tractor these days has a ~2500# rear lift capacity and 40HP. So you want to run a tiller? Your limited by nothing other than HP. So, yes, I understand where the OP is coming from in "thinking" that tractors are underpowered.

Second: dynos dont actually measure HP. They measure torque and the computer calculates HP.
Now as to how its calculated, you are correct. Its done the same way. The dyno dont care about max, peak, continuous, etc. Thats a MFG and engineering thing.

You see, those 400hp+ engines in a pickup......thats a peak rating. Can they indeed make 400hp.....yup. Can they do it all day long.....nope.
So a tractor, that is designed for continuous use, needs to be governed. It needs to be "de-tuned" or (underpowered) down to the point where it can work all day long, and still last a lifetime. If tractors were unleashed, with no governing.....people would be blowing them up all the time.

So, while you "can in theory" make a tractor engine make about double its current HP.......It wouldnt be able to sustain it. Thus, they are regulated down to a power level that they CAN sustain all day long, AND still live a full life.

Yes, you are right, the higher the HP the shorter the life. But, if I were to re-flash the PCM in my 2555 and say get 85HP out of it, that would have very little if any impact on engine longevity.

Also, the Mahindra 2565 Shuttle Cab sells for $41,230, the 2555 Shuttle Cab sells for $36,680. They are the exact same tractor except for that 10 HP, which Mahindra makes you pay $4,550 for. Why should we pay over $4500 for a messily 10HP?

This is done across the board, all makes, all sizes of tractors. Its actually cheaper for the MFG to use a LARGE engine, just de-tune it a bit, and meet a lower HP point. Rather than casting a whole new engine block and associated parts. And yes, many times the next bigger HP model, has nothing dont to it other than different programming. Though sometimes there are some other slight differences to cooling system, or drivetrain to handle the extra power, but not always.

You ask why charge $4k+ more for it......simple economics. Supply and demand. They charge more because they can.

Look at johndeere 7x30 series. All have a 414.4 cu in 6-cylinder
7130.........125hp
7230.........135hp
7330.........150hp
7430.........166hp
7530.........180hp

Granted there are some other differences on those models as well. But in your example of the mahindra 2555 and 2655......does it cost mahindra the same amount of money to build each, probably, since its only a difference in computer programming. But if they sold the tractors for the same amount of money.....do you think they would ever sell any of the 2555's? They might as well not even have that model in their lineup. And to have a totally different engine design (rather than just de-tuning an engine) for every HP point they sell at.....would drive to cost of the tractors up across the board. The would have to stock lots more parts, etc.

So instead of looking at it like that extra 10hp costing $4500 being a rip-off. Think of it in terms of getting a really good deal on a 2555 by giving up 10hp.

 

[Gary Fowler]

HP is HP they are all tested/rated on the same type of dyno. I had never seen a dyno that test continuous horsepower.
First off, when the dyno test of a tractor is performed at full throttle, that is continuous HP for that engine since tractor engines are designed to run full throttle all day long 24/7 for years and years if needed. The same engine lets say at tractor HP is 100 HP might be rated for a different circumstance as in a truck or other industrial uses at much more HP and as such might be tweaked up to produce double the HP of its use on a tractor but you can bet that the engine isn't going to last as long producing 200 HP as it will running at 100. 30-50 years ago it was rare to find a tractor engine turning more than 1900 RPM but now some will run almost 3K and I doubt that you will see those engines still running 40-50 years from now like the old iron tractors of yester year are doing.


The Cummings 4BT and the 6BT are both sold for automotive and industrial use, i.e. genset, Isuzu does the same thing. The engines from the big three would last just as long in a tractor.

That is not entirely true. Big truck engines can go a million miles in many cases before overhaul. So @ 60 MPH that equates to a little over 16,000 hours at varying RPM but mostly at cruise speed of 60-75 MPH. If you took that automotive engine that routinely runs in a big truck at 1500 RPM cruising with the occasional rev to max RPM and revved it to max throttle full time, it isn't going to last as many years as a tractor engine that maxes out at 2000+ RPM full time. It is not uncommon for a tractor engine to last more than 15000 hours without any mechanical problems and that is running in adverse conditions of dust and grime compared to highway conditions of a large truck + most farm tractor hours are put on at full or near full load on the engine. Farmers have been know to boost the HP on their tractors by 25% or so, but in doing so, it cuts the life time proportionally. Life expectancy of an engine is determined by the RPM x HP rating / designed total RPM rating.

Just as the top fuel dragsters might pull 6000 HP @10,000 RPM out of their engine it only runs 4-5 seconds at that HP before having to be torn down and rebuilt. That equates to less than 1000 rotations of that engine. Take that same engine (minus all the HP boosters) and put it in a car and it would run for many years and miles.

 

[gladehound]

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

The guy standing behind the tree and filming must have seen straps, tow ropes, hooks or such break before

Good thinking[/QUOTE]

Yes, there was some concern from all of us that something might give, most likely on the side of the car. That was the reason for the motorcycle helmet and jacket as well as the carry all in the raised position, as well as the guys filming from behind trees.

 

[RaydaKub]

This is done across the board, all makes, all sizes of tractors. Its actually cheaper for the MFG to use a LARGE engine, just de-tune it a bit, and meet a lower HP point. Rather than casting a whole new engine block and associated parts. And yes, many times the next bigger HP model, has nothing dont to it other than different programming. Though sometimes there are some other slight differences to cooling system, or drivetrain to handle the extra power, but not always.

You ask why charge $4k+ more for it......simple economics. Supply and demand. They charge more because they can.

The exact same thing is done in computer systems. Having worked at a large blue computer mfg'er for many years, I can tell you that we would have several computer models for sale. The box was the same, but the performance varied a lot. They would do this by running the top model full out, the next model would have have 1 out of every 5 clock cycles do nothing for an 80% model, the 3rd model would have 2 of every 5 clocks do nothing for 60% and so on. Another technique would just be to slow down the clock itself.

A little off topic, but just for fun.

 

[TomSeller]

Uhm. 650HP

Largest John Deere Tractor to Hit the Marketplace | Agweb.com

Do you think it could out pull that Toyota Echo?

 

[woodlandfarms]

Do you think it could out pull that Toyota Echo?

The Echo could pose a problem, tough car with plenty of traction...

962R Pull - YouTube

The New John Deere 9RX Series Tractor - YouTube

John Deere 215 Products Launch - 9R/9RT Tractors - YouTube

 

[gladehound]

Do you think it could out pull that Toyota Echo?

Maybe if you took the chains off the Echo's tires :laughing:

 

[jenkinsph]

Do you think it could out pull that Toyota Echo?

If it did pose a problem just pick it up and carry it.

 

[WilliamBos]

One should consider longevity too. Tractor engines are not stressed at all (assuming the operator isn't an idiot). You'll find decades old diesels still running and have never been overhauled.

Those are the ones that may work 200 hours a year. Not uncommon to have 800-1200 hours per year on farms like dairies. A new tractor should give 10,000 trouble free hours.

 

[adventure bob]

I guess I'm completely confused...Tractors are underpowered for what? If you are going to make a claim like that then you have to use the comparative case. Tractors are underpowered for (insert task here). That does not seem to be the case with this post. This seems to be a complaint that over the light truck or passenger car diesels are somehow better than tractor diesels. First, the big three doesn't make a small diesel to compare a tractor to. GM and Ford don't make commercial diesels for pickups or cars for that matter. They make a light duty aberration of diesel. The Cummins is the closest thing to a commercial engine that's going in trucks because, well its based on a commercial engine. It would seem by the logic of this thread that the Freightliner Cascadia is underpowered at 350-600HP. Following the argument here, a truck that big should be pushing over a 1000HP. Its not that it can push 350-600hp, its that it can do it at 80% duty cycle for a million miles. There's design parameters for ag engines and commercial engines that simply don't apply to OTR passenger diesels.

 

[Snobdds]

Like other have said, one has to understand duty cycle to understand why a tractor is under-powered...in name only.

Take for example a 6.7 powerstoke. The 6.7 that comes in the F250, F350 is rated around 400 hp and 900 Ft/lbs of torque depending on year. That same engine is put into the F450, F550 F750 etc. However, the engine is only rate around 300 hp and 625Ft/lbs of torque. Ford does this because the engine will last about twice as long with lower power than if the juice is turned up.

Another example: compare a 12 liter OTR diesel engine to a 6 liter light duty diesel found in 3/4 and 1 ton trucks. The OTR diesel is about twice as big as a light duty diesel, but the HP and torque can be made to be about equal on both . The OTR diesel is twice as big but works 1/2 as hard as the light duty diesel.

It's a tried and true method of making engines last. However, the big three should be commended that they can produce a diesel that produces so much power and has the reliability they do.

 

[deezler]

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?

We understand what you are saying but you are just thinking about it all wrong. If you took a 2.6L in the Mahindra 2555 and doubled its power, you'd just have to overbuild the frame, driveline, transmission, and axles to handle all that power getting used aggressively. Not to mention a loader or any other attachment that would then be subject to greatly increased forces. Finally you'd need more weight to even put that power to the ground (TRACTION) in an effective way anyway. Keeping the engine's specific power output lower keeps the tractor more reliable, fuel efficient, and affordable. if you need a tractor with more power, they are readily available. Don't view the low specific output as a fault - it is precisely as intended.

Comparing to road-going cars and trucks is pretty silly anyway. They need lots of HP to accelerate quickly, maintain highway speed up a mountain, or tow a heavy load. But honestly most cars and trucks right now have about double the power they actually need. It's simply a marketing war of numbers, and has gotten quite ridiculous.

 

[mike69440]

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.

Actually GM advertises 445 HP, Ford Is 440 hp, 925 f-Lbs, per Ford. Cummings is a bit less, but nothing that can't be fixed.

 

[dodge man]

One thing I don't know has been discussed it weight. Trucks and cars aren't exactly like airplanes, but weight has gotten critical. Less weight, better fuel mileage, more weight you can carry for cargo. In a tractor, weight isn't critical, in fact most people add weight, so its often easier and cheaper and adds more durability just to put a larger displacement engine in a tractor since the extra weight isn't a bad thing.

 

[Btown]

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.

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.

 

[dodge man]

I think if you took actually readings, even when towing a heavy load, engines in a modern diesel pickup aren't any where near 100% power output very often. A tractor on the other hand, say when brush hogging heavy grass or plowing a field, might be at 90% power rating or higher for long periods of time.