Why are tractors so under-powered?

[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.