Why are tractors so under-powered?

[Garandman]

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...

Boat engines operate under full load for extended periods.

From what I can find design life for marine diesels (Yanmar is very popular) is 8,000 hours. Many go over 10,000 hours.

If you averaged 40mph that would be 320,000 miles. Our fleet vehicles calculate average speed and it's more like 48mph or 384,000.

 

[hayden]

Boat engines operate under full load for extended periods.

From what I can find design life for marine diesels (Yanmar is very popular) is 8,000 hours. Many go over 10,000 hours.

If you averaged 40mph that would be 320,000 miles. Our fleet vehicles calculate average speed and it's more like 48mph or 384,000.

Exactly. That's the concept. Except most Yanmars I think are rated for some intermediate duty, not continuous. In marine and industrial applications there are usually 3-5 different ratings, starting with continuous full power, then working it's way down to a smaller and smaller % of operating time at full power. When you think about vehicular duty, full power is only a very small % of the operating time. For tractors and industrial equipment, it's often 100% of the time. Marine varies, with commercial use at continuous duty, and pleasure use much lower.

 

[jenkinsph]

I would suspect that the 400+ hp. pickups can produce these power levels measured in minutes of duration while a tractor can produce their rated output for days. I do think that the cooling system is a big factor in all of the uses, marine engines have an advantage here. Cooling systems in all of these have improved quite a bit over the last 60 years or so. Years ago it was common to see over heated vehicles on the side of the road while climbing mountain passes, rare today.

The engine is only one part of the story, in most cases the drive train needed to handle more hp. is more costly than the engine upgrade. When you option for more hp in a medium duty truck the engine upgrade may be 1 to 2 grand but the drive train upgrade may be 8 to 10 grand.

Just my opinion but tractor hp. is matched pretty close to tractor size, weight and operating speeds by all manufacturers.

 

[s219]

Tractors are very different from cars/trucks in many ways. Think about how many newbies here on TBN discover that work with tractors is not limited by power, but by traction or weight. Wouldn't matter if the tractor had 10X more power. So much of what we do with tractors comes down to traction, weight, and hydraulics. Except for PTO operations, in most cases more power could never be utilized. Even PTO based implements have their limits.

 

[IH782]

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.

HP is HP they are all tested/rated on the same type of dyno. I had never seen a dyno that test continuous horsepower.


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.

 

[Oldpath05]

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

But on the other hand you might be able to mow your lawn in 2 min, vs 2 hr!! <Tim the Tool Man way.

 

[motownbrowne]

HP is HP they are all tested/rated on the same type of dyno. I had never seen a dyno that test continuous horsepower.


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.

I'm not sure you're seeing the point. Yes, HP is HP. You could adapt a 250 HP motor from a hopped up street none into a tractor that has a 250 HP motor. Same amount of HP, right? Now go cut hay all day at 90% of maximum power output. Which motor survives the day?

Yes, the Cummins motors, which are good motors, are used for industrial applications where they run 100% of their power rating for weeks on end BUT it's a different rating than when they get strapped into a truck. I have a Ford 300 six cylinder in my truck. It's a legendary motor. Mine makes 140 HP. People build them up to 300 pretty easily. They are also used on pumps, in heavy equipment, and on a wood chipper I used to run. The wood chipper motor (same motor) only made maybe 60 HP. The reason for this is that my truck can't make 140 HP all day every day. That chipper can make 60 HP all day every day. See what we're saying here?

A new truck with a 500 HP motor can't put that power out for hours at a time without melting down. They can make a ton of power, yes, and climb mountain passes to your heart's content, but they still can't hook up to a PTO shaft and use 500 HP all day.

 

[pmsmechanic]

HP is HP they are all tested/rated on the same type of dyno. I had never seen a dyno that test continuous horsepower.


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.

On the first part I agree. A dyno just displays horsepower. It's the settings on the injection pump that determine the horsepower available.

"The engines from the big three would last just as long in a tractor." Never! They aren't designed to run at full rated horsepower all day like an industrial engine. The epa rates the Duramax and the Powerstroke as light duty diesels. The Cummins is rated at medium duty. It might have a chance but I doubt it.

Industrial versions of these engines are a different story. They will run all day at maximum rated horsepower because they are designed for it. An engine just plucked out of an automotive application and then put to work at full rated horsepower will destroy itself.

 

[Oldpath05]

Why are tractors so under-powered?<<<This is a good way to get most tractor folks attention like me, see this topic and go WHAT?
This is probably a question from the guys who like those 100 mi/hr tractors at fairs would ask. As far as my L3400 goes, I'm amazed at the horse power that come's from such a small engine, but I dont go 100 miles/hour either. A better question from me would be, Why are 4 wheel drive tractors 3 wheel drive?

 

[IH782]

I'm not sure you're seeing the point. Yes, HP is HP. You could adapt a 250 HP motor from a hopped up street none into a tractor that has a 250 HP motor. Same amount of HP, right? Now go cut hay all day at 90% of maximum power output. Which motor survives the day?

Yes, the Cummins motors, which are good motors, are used for industrial applications where they run 100% of their power rating for weeks on end BUT it's a different rating than when they get strapped into a truck. I have a Ford 300 six cylinder in my truck. It's a legendary motor. Mine makes 140 HP. People build them up to 300 pretty easily. They are also used on pumps, in heavy equipment, and on a wood chipper I used to run. The wood chipper motor (same motor) only made maybe 60 HP. The reason for this is that my truck can't make 140 HP all day every day. That chipper can make 60 HP all day every day. See what we're saying here?

A new truck with a 500 HP motor can't put that power out for hours at a time without melting down. They can make a ton of power, yes, and climb mountain passes to your heart's content, but they still can't hook up to a PTO shaft and use 500 HP all day.

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?