Does HP matter?

[MARKMILES77]

If two tractors have identical peak torque but one has more power than the other is there any point in getting the tractor with more horsepower?
For example the JD 3032E has 31.4 Hp while the JD 3038E has 37 HP but they have identical peak torque.
Are those extra horses useless?
I would have thought that for heavy work like rotary cutting thick scrub that the extra horses would not help?


Mark

 

[mjncad]

Ask a woman if size matters. :laughing:

Seriously now, do the peak torque and HP numbers occur at the same RPM's between the engines? If the extra HP's don't cost a lot extra, I'd go with the 37HP unit as it in theory will get you an extra foot of brush-cutter width using the rule-of-thumb of 5HP per 1-foot of brush-cutter width.

 

[creekbend]

There is a difference of five-5 HP - PTO in those two models. TractorData.com - information on all makes and models of tractors

 

[JD 4520]

Get more HP if you can. You won't later regret it.

 

[KennyG]

Torque is a measure of force while horsepower is a measure of work done so, yes, higher horsepower is useful. If two engines have the same torque but one has higher horsepower, it means the higher powered one will develop that torque at a higher engine speed and do more work. In the case identified above, different causes could exist, but if both are geared to produce maximum power at the PTO speed, the higher horsepower tractor will put more energy into the driven device and do more work.

The only case in which this wouldn't work is if both tractors have the same gearing and the higher horsepower tractor only produces the greater horsepower beyond the PTO speed, in which case the extra power can't be used when using a PTO powered implement.

If you look at tractors, you will find that PTO horsepower is almost always less than engine horsepower. Theres a bit of drivetrain loss but most of that is because the torque curve is very flat and the engine will rev somewhat past the PTO rated speed.

 

[bcp]

Depends if you are pulling or powering, too.

A heavier tractor with a smaller engine will often outpull a lighter one with a larger engine. Weight makes traction, horsepower lets you run bigger powered implements or do the work faster.

Bruce

 

[EE_Bota]

Horsepower is work per unit time. Work/per hour, etc. All things being equal, I'd go for the higher horsepower. But I don't say that lightly. You supplied an important point: the torque is equal. But you didn't say what your travel speed limitations are...so I presume low range low gear will be slow enough for you on both tractors.

The reason it matters is motors always have to be coordinated with gear box ratios. These modify the torque and the speed, and you'd be surprised how many situations I have walked up on in an industrial environment where folks choose a certain HP first because they have a rule of thumb about how much power a machine will take. Then, they meet with production people who ask for extremely fast speeds so the engineer just changes the gearbox ratio and then purchases the machine. Then in production at normal speeds, the device doesn't have the final torque to run the process, but unloaded it can run fast as heck! It's disheartening when I see that happen, but I doubt it will happen with your tractor choices.

 

[hodge]

Dollars to donuts the torque peak is at different RPM's between the two engines. HP and torque numbers are only part of the equation; where in the RPM range that they happen is important, too.

 

[murphy1244]

Dollars to donuts the torque peak is at different RPM's between the two engines. HP and torque numbers are only part of the equation; where in the RPM range that they happen is important, too.

Good advice, I would take the machine that peaks at a lower RPM assuming same same.

 

[KennyG]

Good advice, I would take the machine that peaks at a lower RPM assuming same same.

But the original question was about bushhogging. For that application you would want the machine with the highest PTO horsepower since you will be running at the PTO rated RPM.

 

[DarkBlack]

All valid posts. I will only add that if you are really interseted in the question, than you need to get the torque vs rpm graph for both engines.
Since a real use engine will be run a high amount of time outside it's "peak torque" rpm, you will want to know how gradually the torque decreases, above, and below that advertised rpm value.
One engine may have the same torque #, and a higher HP rating, but could have less real world useful power due to a sharply falling torque curve. Another engine may have the same torque rating, but a lower HP rating, but have a real world better power response because of a wider torque band.

 

[murphy1244]

But the original question was about bushhogging. For that application you would want the machine with the highest PTO horsepower since you will be running at the PTO rated RPM.

True, But he answered the ? better.

 

[Jerry/MT]

If two tractors have identical peak torque but one has more power than the other is there any point in getting the tractor with more horsepower?
For example the JD 3032E has 31.4 Hp while the JD 3038E has 37 HP but they have identical peak torque.
Are those extra horses useless?
I would have thought that for heavy work like rotary cutting thick scrub that the extra horses would not help?


Mark

Max horsepower is really important if you are going to use it.

It's more often used as a marketing point to say the Big Green tractor has more HP thean the Big Blue tractor so the owners can brag over morning coffee.

Guys that use their machines for primary tillage in tough ground, lots of acres, big implements, and a narrow planting window use that rated horsepower. Having said that most, compact tractor owners don't operate under those conditions.

Another issue, just to complicate matters, is that newbies often undersize their tractors and then find out they could do more if they had more power and weight so they start looking for a bigger machine.

I'll repeat my first statement. Max horsepower is really important if you are going to use it.

Where are you at with your tractor?

 

[jenkinsph]

If two tractors have identical peak torque but one has more power than the other is there any point in getting the tractor with more horsepower?
For example the JD 3032E has 31.4 Hp while the JD 3038E has 37 HP but they have identical peak torque.
Are those extra horses useless?
I would have thought that for heavy work like rotary cutting thick scrub that the extra horses would not help?


Mark

According to tractordata the torque for the 3032E is 80ftlbs @ 1680 rpms', the 3038E is 88ftlbs @ 1680 rpms'. That is a difference of 8 ftlbs or 10% increase further the 3038E will turn 2500 rpms' which is 100 more than the 3032E. All of that said I wouldn't consider them to be the same.

 

[arrow]

Max horsepower is really important if you are going to use it.

It's more often used as a marketing point to say the Big Green tractor has more HP thean the Big Blue tractor so the owners can brag over morning coffee.

Guys that use their machines for primary tillage in tough ground, lots of acres, big implements, and a narrow planting window use that rated horsepower. Having said that most, compact tractor owners don't operate under those conditions.

Another issue, just to complicate matters, is that newbies often undersize their tractors and then find out they could do more if they had more power and weight so they start looking for a bigger machine.

I'll repeat my first statement. Max horsepower is really important if you are going to use it.

Where are you at with your tractor?

There are a bunch of good posts here. I think this one is the most pertinent. If you are a "traction" user, I do not think hp means as much than if you were an "rpm" user such as bush hogging or grass cutting. Usage type zeros in on the pertinent answer for your particular needs. I have a tractor that weighs about as much as the tractors you are mentioning. It has 20 Hp. I have lost traction long before I have lost grunt. A thirty hp engine in this tractor will make absolutely no difference in how I use my tractor as it does not weigh enough to overcome even 20 hp traction wise.

 

[nwngunner]

Horse power does matter, not only will more horse power let you work faster and do more at the same time, when you are not maxed out the more horse power will save you fuel.


Lets say your bigger hp engine burns 15% more fuel per hour then the little one. How ever if you can do 30% more work makes a difference. Case in point i have an oliver 1650 and a farmall 806. When i was disking one year i had to run 3rd gear on the oliver. I ended up hooking up a big disk to the 806 was able to run in 4th low and was done in half of the time. While burning 10% more fuel per hour.

Also even with wore out tires the 806 done a much better job with ground engaging work because of the massive weight difference in the two tractors. I know i am comparing old farm iron to new compact utility tractors but it still applies.

 

[arrow]

Horse power does matter, not only will more horse power let you work faster and do more at the same time, when you are not maxed out the more horse power will save you fuel.


Lets say your bigger hp engine burns 15% more fuel per hour then the little one. How ever if you can do 30% more work makes a difference. Case in point i have an oliver 1650 and a farmall 806. When i was disking one year i had to run 3rd gear on the oliver. I ended up hooking up a big disk to the 806 was able to run in 4th low and was done in half of the time. While burning 10% more fuel per hour.

Also even with wore out tires the 806 done a much better job with ground engaging work because of the massive weight difference in the two tractors. I know i am comparing old farm iron to new compact utility tractors but it still applies.

What needs to be considered here are the two tractors the op is mentioning. Both around 2000# and approximately 6 hp more for one than the other. The price difference is more substantial. If you do not have the traction aid of a heavier weight, one is wasting money with more hp in this case unless one is needing the more rpm. If you could put a 6' cutter on the larger hp model as opposed to a 5' cutter on the smaller, then you could save some time however if you are hauling a 20' oak stem, the added hp of the larger hp model without the benefit of being a heavier tractor is just a waste of hp and money. No matter what, you can only go just so fast through the woods dragging a 2000# log. This is why it is so important for the user to know how he is using the tractor. Don't forget, the first JD tractor ever to have been painted green was a 4000 Lb tractor able to pull 3000 #. I think it did not have any more than 10 flywheel hp. In this case, traction is king and not speed. Your point is valid for tractors of much different weights when ground engaging. As none of us know how the op is using his tractor, everyone's opinion including mine is a crap shoot. I have yet to read any post on this subject that does not have possible, applicable validity.

 

[LD1]

Torque is a measure of force while horsepower is a measure of work doneIn a given time so, yes, higher horsepower is useful. If two engines have the same torque but one has higher horsepower, it means the higher powered one will develop that torque at a higher engine speed and do more workIn a given amount of time. In the case identified above, different causes could exist, but if both are geared to produce maximum power at the PTO speed, the higher horsepower tractor will put more energy into the driven device and do more workIn a given time.

Most imprtantly, Horsepower adds the TIME element that people often forget.

It is unlikely that both make the exact SAME torque with differing HP, BUT...if they do, The 38HP tractor CANNOT do ANY more work than the 32HP tractor. In fact, if torque is the same, the amount of work they CAN do will be the EXACT SAME.

BUT....The higher HP machine CAN do the same work FASTER.

 

[DarkBlack]

Most imprtantly, Horsepower adds the TIME element that people often forget.

It is unlikely that both make the exact SAME torque with differing HP, BUT...if they do, The 38HP tractor CANNOT do ANY more work than the 32HP tractor. In fact, if torque is the same, the amount of work they CAN do will be the EXACT SAME.

BUT....The higher HP machine CAN do the same work FASTER.

I beg to differ on your middle statement above. Two differnt engines, with the same max torque, but one can develop higher HP, most certainly CAN do more work. You missed that HP already contains the time element. It's call RpM's, which with gearing produces more torque.

 

[LD1]

I beg to differ on your middle statement above. Two differnt engines, with the same max torque, but one can develop higher HP, most certainly CAN do more work. You missed that HP already contains the time element. It's call RpM's, which with gearing produces more torque.

If torque is the same, work that CAN be done is the same.

You can ALWAYS gain torque by gearing. Thats no secret. But HP remains constant (minus a little frictional losses).

If you can gear the the higher HP machine to do more work, you can ALSO gear the lower HP machine to do just as much work. (IF the engine starts off with the same torque)

And the RPM's have nothing to do with the time element of HP. All the RPM's mean is THAT is the point that they measured the HP. Two totally different things. RPM is just the point at which the measurment is taken.

You can take a 100hp engine with 100ft lbs of torque, and then you can take a 20hp engine with the SAME 100ft-lbs, and the work they are ABLE to do is exactally the same. The 100hp engine will just be quicker is all.