How much does engine horsepower really matter?
Page 1 of 4 1 2 3 ... LastLast
Results 1 to 10 of 33
Like Tree80Likes

Thread: How much does engine horsepower really matter?

  1. Top | #1
    mike01's Avatar
    Join Date
    Mar 2017
    Last Online
    Today @ 06:47 AM
    Location
    NY
    Posts
    1,251
    Thanks
    34
    Thanked 158 Times in 104 Posts

    How much does engine horsepower really matter?

    How much does engine horsepower matter in a tractor? What exactly does the engine do besides spin the transmissions hydraulic pumps? Isn't the transmission the thing that's putting out all of the actual power, driven by the engine?

    Like...if you take two 20hp engines and hook one up to a powerful transmission, say a TuffTorq K90, and the other to a K46, will they put out the same power to the wheels? Or will the K90 give you more wheel hp? How does this work and why?
    2019 X758, 54" Autoconnect deck
    2018 2032R, 220R Loader, dual rear SCV, hydraulic top link, SB1164 Snow Blower, RC2072 rotary cutter, BB5048L box blade, 42" Titan forks, BB2060L back blade

    Owned in the past:
    X570, X758 (2015), 1025R, X590

  2. Remove Advertisements
    GreenTractorTalk.com
    Advertisements
     

  3. Top | #2
    RodW's Avatar
    Join Date
    Mar 2018
    Last Online
    Today @ 12:10 PM
    Location
    NW Florida
    Posts
    379
    Thanks
    12
    Thanked 116 Times in 77 Posts
    Quote Originally Posted by mike01 View Post
    How much does engine horsepower matter in a tractor? What exactly does the engine do besides spin the transmissions hydraulic pumps? Isn't the transmission the thing that's putting out all of the actual power, driven by the engine?

    Like...if you take two 20hp engines and hook one up to a powerful transmission, say a TuffTorq K90, and the other to a K46, will they put out the same power to the wheels? Or will the K90 give you more wheel hp? How does this work and why?
    The only things that provide power are the battery and the engine. Different transmissions may transmit that power more efficiently, or have more durability, or provide relatively more torque at the low end or high end, but the engine HP determines power. Also, tires make a difference in utilizing the power and torque based in their gripping ability. All of these things determine overall performance, which is what I think you mean by power.
    I'll let someone else present the math...
    X350 (2016) and Accessories
    Assorted Stihl & Grizzly tools
    My wife says that's all I need for my measly 1/2 acre...

  4. Top | #3
    Zebrafive's Avatar
    Join Date
    Apr 2012
    Last Online
    Today @ 01:52 PM
    Location
    South West Michigan
    Posts
    7,171
    Thanks
    1,521
    Thanked 597 Times in 523 Posts
    Horsepower is a unit of work per time. More HP can either do more work in the same amount of time, or the same amount of work in less time.

    IF,( and I say IF, because I am MAKING THESES NUMBERS UP!!!!) One horse can lift (think rope and pulley on barn beam) 2000lbs 1 foot in one minute. TWO horses will lift this same 2000lbs 1 foot in 1/2 minute. OR 4000lbs 1 foot in one minute. More horse power either can do the SAME amount of work (lift 200lbs 1 foot) in less time, Or do MORE work (lift 4000lbs 1foot) in the same amount of time.
    J
    John Deere 2030 w/245SL Loader
    John Deere 6415 w/640SL Loader
    John Deere 285 50" deck Stolen May 2017
    John Deere x485 62" deck AWS
    Kawasaki Mule 2510 4x4 bought new 1996
    Ford F250 4x4 bought new 1978

  5. Remove Advertisements
    GreenTractorTalk.com
    Advertisements
     

  6. Top | #4
    mike01's Avatar
    Join Date
    Mar 2017
    Last Online
    Today @ 06:47 AM
    Location
    NY
    Posts
    1,251
    Thanks
    34
    Thanked 158 Times in 104 Posts
    Quote Originally Posted by RodW View Post
    The only things that provide power are the battery and the engine. Different transmissions may transmit that power more efficiently, or have more durability, or provide relatively more torque at the low end or high end, but the engine HP determines power. Also, tires make a difference in utilizing the power and torque based in their gripping ability. All of these things determine overall performance, which is what I think you mean by power.
    I'll let someone else present the math...
    Well it's a little different with hydrostatic tractors. In a car, the engine, via the transmission and axles, is what spins the wheels. In a tractor, the engine spins the hydraulic pumps in the transmission, and the hydraulic pressure generated by the pumps (powered by the engine) is what moves the tractor.

    So the engine matters, obviously. But what I want to know is how much it matters, and how its power is transferred. For example, you can get a 25hp lawn tractor at Lowe's. Its engine really makes 25hp, that's not a lie. But if you put it up against an 18hp Kubota subcompact tractor, that Kubota is going to wreck that lawn tractor in every respect, even though the lawn tractor has almost 50% more horsepower.
    johncanfield likes this.
    2019 X758, 54" Autoconnect deck
    2018 2032R, 220R Loader, dual rear SCV, hydraulic top link, SB1164 Snow Blower, RC2072 rotary cutter, BB5048L box blade, 42" Titan forks, BB2060L back blade

    Owned in the past:
    X570, X758 (2015), 1025R, X590

  7. Top | #5
    RodW's Avatar
    Join Date
    Mar 2018
    Last Online
    Today @ 12:10 PM
    Location
    NW Florida
    Posts
    379
    Thanks
    12
    Thanked 116 Times in 77 Posts
    Quote Originally Posted by mike01 View Post
    Well it's a little different with hydrostatic tractors. In a car, the engine, via the transmission and axles, is what spins the wheels. In a tractor, the engine spins the hydraulic pumps in the transmission, and the hydraulic pressure generated by the pumps (powered by the engine) is what moves the tractor.

    So the engine matters, obviously. But what I want to know is how much it matters, and how its power is transferred. For example, you can get a 25hp lawn tractor at Lowe's. Its engine really makes 25hp, that's not a lie. But if you put it up against an 18hp Kubota subcompact tractor, that Kubota is going to wreck that lawn tractor in every respect, even though the lawn tractor has almost 50% more horsepower.
    No argument there, but you can't asses a single system component independently since overall performance depends on everything in the power train. Lawn tractor and garden tractor transmissions are built for different uses and are generally paired with different tires. Adding more power to a lawn tractor doesn't make it competitive with garden tractors when torque or heat dissipation are important. The overall design is optimized for different uses. It would help to define the intended use. If you want to use cleated tires and pull ground contact implements, you need a certain class of transmission. You can then compare various engines and horsepower ratings for that application. Otherwise, there are too many variables to know what the actual engine contribution is. (Some of the engine power goes to the mower deck as well so deck size also comes into play.) Too much horsepower with a K46 might actually be a bad thing if it increases heat buildup.
    Last edited by RodW; 06-15-2018 at 11:12 PM.
    johncanfield likes this.
    X350 (2016) and Accessories
    Assorted Stihl & Grizzly tools
    My wife says that's all I need for my measly 1/2 acre...

  8. Top | #6

    Join Date
    Mar 2015
    Last Online
    Today @ 07:01 AM
    Location
    Eastern Virginia, United States
    Posts
    4,483
    Thanks
    341
    Thanked 812 Times in 529 Posts

    Traction and torque

    Quote Originally Posted by mike01 View Post
    Well it's a little different with hydrostatic tractors. In a car, the engine, via the transmission and axles, is what spins the wheels. In a tractor, the engine spins the hydraulic pumps in the transmission, and the hydraulic pressure generated by the pumps (powered by the engine) is what moves the tractor.

    So the engine matters, obviously. But what I want to know is how much it matters, and how its power is transferred. For example, you can get a 25hp lawn tractor at Lowe's. Its engine really makes 25hp, that's not a lie. But if you put it up against an 18hp Kubota subcompact tractor, that Kubota is going to wreck that lawn tractor in every respect, even though the lawn tractor has almost 50% more horsepower.
    Two other items come into play in that example. One, the two engines are very likely horsepower rated at different RPMs. Since horsepower is calculated by torque x RPM/a constant the faster the engine turns the more horsepower. It's likely the 25 hp Briggs would have been rated at 3,600 rpm while the Kubota may have been rated at 2,400 rpm. The Kubota could very well have more torque at rated rpm than the Briggs at it's rated rpm but the horsepower is different. https://www.briggsandstratton.com/na...que-value.html

    Since torque is what moves things, the Kubota will outpull the lawn tractor either at the wheels or in a pto/blades. The other issue of course is traction. The subcompact tractor will generally have a lot more traction on the ground even without 4 wd.

    Treefarmer
    johncanfield and PJR832 like this.
    John Deere 790, 300 loader w Ken's Bolt on Hooks & Piranha tooth bar, grapple, back blade, box blade, Bush Hog mower, couple of red tractors, hay equipment, various old stuff some red, one orange, some I don't remember

  9. Top | #7
    RodW's Avatar
    Join Date
    Mar 2018
    Last Online
    Today @ 12:10 PM
    Location
    NW Florida
    Posts
    379
    Thanks
    12
    Thanked 116 Times in 77 Posts
    Quote Originally Posted by Treefarmer View Post
    Since torque is what moves things, the Kubota will outpull the lawn tractor either at the wheels or in a pto/blades. The other issue of course is traction. The subcompact tractor will generally have a lot more traction on the ground even without 4 wd.

    Treefarmer
    Good point. Sometimes advertised numbers are a distraction. Many pressure washer ads focus on the engine, when almost all failures occur in the pump. Sears used to brag about "max developed horsepower" -- which was only possible in the moments right before the motor burned up. On my X350, the tires spin long before I run out of power. Horsepower is an easy selling point, but beyond a certain threshold, differences may mean very little for the tasks you want to perform. These discussions set dealers apart from resellers. Good dealers know the system performance and you can make direct comparisons there.
    Last edited by RodW; 06-16-2018 at 07:35 AM.
    coaltrain and johncanfield like this.
    X350 (2016) and Accessories
    Assorted Stihl & Grizzly tools
    My wife says that's all I need for my measly 1/2 acre...

  10. Top | #8
    coaltrain's Avatar
    Join Date
    May 2014
    Last Online
    Today @ 02:18 PM
    Location
    NW Penna
    Posts
    19,802
    Thanks
    1,058
    Thanked 3,061 Times in 2,226 Posts
    I feel as far as homeowner type equipment goes (lawn tractors etc.) that horsepower has become more of a marketing tool than anything else.

    When Joe homeowner goes to Lowe’s or Walmart to look at lawn tractors he will look at 2 different units - one with 20hp and one with 25hp. Well the 25hp one has to be better, right? He will never look at the build quality of the deck or anything else for that matter.

    When a discussion like this comes up I always like to use an example like this....

    Take a Deere model B. It has 12hp at the drawbar and 16hp at the belt. Look at the size/weight of that machine and all the work it can do.

    Click image for larger version. 

Name:	26B10E2A-CB19-434B-85AD-F1D2A1F769EC.jpg 
Views:	17 
Size:	90.3 KB 
ID:	632250
    ~Stan~
    It is what it is
    Knowledge is power, ignorance is bliss
    2520 w/200CX w/62D2

  11. Top | #9
    Keeper of the GTT Cookies dieselshadow's Avatar
    Join Date
    Nov 2011
    Last Online
    Today @ 11:53 AM
    Location
    Joelton TN
    Posts
    19,774
    Thanks
    1,065
    Thanked 4,289 Times in 2,580 Posts
    HP is a mathematical figure based on torque x RPM / 5252. So if you increase either torque number or the RPM number, you make more HP.

    12 HP in a riding mower engine turning 3600 RPM is quite a bit different than the 12 HP being produced by the 1200 RPM engine in the B. They both make 12 HP, same amount of work can be done, at least in theory. But I would rather have the B.
    - Jason

    GreenTractorTalk.com Rules, Policies, and Terms of Use

    Subscribe to dieselshadowman on YouTube

    2720 w/ 200CX FEL
    , Ken's weld-on hooks, Fit Rite Hydraulics Top and Tilt kit, Artillian forks.
    1954 60 - getting full restoration, 1964
    110 round fender in the shop for crustoration
    Ferris IS3200Zzero turn mower

  12. Top | #10

    Join Date
    Jun 2014
    Last Online
    Today @ 11:52 AM
    Location
    Berlin, MA
    Posts
    4,597
    Thanks
    94
    Thanked 867 Times in 662 Posts
    Quote Originally Posted by mike01 View Post
    Well it's a little different with hydrostatic tractors. In a car, the engine, via the transmission and axles, is what spins the wheels. In a tractor, the engine spins the hydraulic pumps in the transmission, and the hydraulic pressure generated by the pumps (powered by the engine) is what moves the tractor.

    So the engine matters, obviously. But what I want to know is how much it matters, and how its power is transferred. For example, you can get a 25hp lawn tractor at Lowe's. Its engine really makes 25hp, that's not a lie. But if you put it up against an 18hp Kubota subcompact tractor, that Kubota is going to wreck that lawn tractor in every respect, even though the lawn tractor has almost 50% more horsepower.
    Keep in mind here that not ALL of the power from the engine is going to the hydro transmission. Some of it is for the PTO as well.

    That said, the internal workings of the transmission is what decides how much of the power going into the transmission gets turned into torque applied to the axles. That tranny has the hydro pump, gears and clutches. Each one effects that path from input to output.

    The K46 is only rated to a max of about 170 ft lbs of torque so not matter how much HP goes in, when it gets to 170 ft lbs of torque being applied to the axle shafts, the internal hydro systems are going to start going into bypass or the clutches are going to start slipping. Any additional HP after that point is wasted.

    If you do the math and you run the K46 with input at 3600 RPM, it's internal gearing is roughly 28:1 and with a max generated torque of 170 ft lb. You end up with a figure of ~4.2 HP. So applying anything more than 4.2 HP to the K46 won't get the tractor to do anything more. It's max'd out.

    If you look at the K90/K92 and do the same math, it's hydro pump, clutches and internal gears are capable of generating ~650 ft lbs of torque to the axles so you end up maxing it out with ~15.8 HP to K90's input.
    Last edited by JimR; 06-16-2018 at 08:27 AM.
    D160 Mower/Bagger.
    2014 2032R tractor/H130 FEL w/Bolt-On Hooks/54" Snow Plow/iMatch Quick-Hitch/County Line 5' Scraper blade/County Line Carry-All/Artillian 42" Forks & QH Adapter/JD Ballast Box/Frontier SB1164 3PH Blower/Leinbach PHD/Wallenstien BX42 Chipper

  13. Remove Advertisements
    GreenTractorTalk.com
    Advertisements
     

Page 1 of 4 1 2 3 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •