Horse power is over rated

Discussion in 'Lawn Mowing' started by Bennett scape, May 2, 2008.

  1. Bennett scape

    Bennett scape LawnSite Member
    Posts: 201

    Hi guys just a thought I have noticed many people on this site go on and on about how you have to have more horse power than anything else. However there are many things to consider about horse power rating. What kind of load is on the engine how is the engine gear box set up how does the transmission work and were does the energy go to from the transmission how is the energy used what is the torque rating etc. I am not saying that HP is not important in a engine i just want to say that the more hp you have may not be the best. for example i have a Scag 08 19 hp kaw Tiger Cub 48" (I love that machine) but before i got it the dealer said the 26 hp Briggs had something lacking in the power area and that the 19 hp had MORE POWER then the 26 hp. any comments questions insults or ideas welcome.
     
  2. C&K

    C&K LawnSite Senior Member
    from East TN
    Posts: 295

    I don't know but i thought hp was hp. Unless B&S wasn't truthful with thier hp rating. But all things equal like, the same pumps and wheel motors on the same mower and the only thing different is the hp of two diferent motors, well you should be able to tell the difference.

    I hope your dealer wasn't just trying to sell you the 19 hp model.
     
  3. Bennett scape

    Bennett scape LawnSite Member
    Posts: 201

    check out wikipedia they have a lot of truthful info in fact i wrote some of it from my knowledge of engines at college.
     
  4. yungman

    yungman LawnSite Bronze Member
    from Calif.
    Posts: 1,274

    There is torque also. And hp rating at what rpm.
     
  5. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    There's also rated or working horsepower and maximum horsepower.

    Maximum HP is the number that the engine manufacturer usually puts on the engine. Your Kaw had 19 Max HP and that Briggs had 26 max HP.

    The rated HP is usually somewhat lower. Around 20%. That is the amount of power that the engine manufacturer recommends to the mower manufacturer (or whatever piece of equipment the engine is going into) to use to design the load calculations for the mower's needs. The reason there is a rated HP is because if an engine is operated at it's max HP for an extended period of time it will wear out prematurely.

    Here's the HP/Torque graph from a 19 HP Kawi engine. You'll see what I'm talking about. BTW, Kawi calls it the Recommended Maximum Output.

    http://www.kawpowr.com/images/engines/4cycle/fh580v_specs.gif
     
  6. supercuts

    supercuts LawnSite Silver Member
    Posts: 2,785

    like richard said, most companies advertise their max HP, which the engines do not opporate at when set up by the factory. my understanding is that they are legally able to market the engine at a 20% higher rating then it achieves. that was one of the marketing highlights on my newer bobcat with the 33hp generac engine, they claimed it was a true working HP rating, not an inflated number that most manufactures use.

    another point is my 84' kubota backhoe with a 16hp diesel seems to outperform just about anything new in a higher HP. ive rented b21's (21HP) and mine will outwork the machine rented. ive also used an 18 hp termite backhoe ( gas engine) and that thing did surprising well digging, better than the b21. like you said,im sure it has alot to do with pumps and presure relief valves etc.
     
  7. topsites

    topsites LawnSite Fanatic
    Posts: 21,653

    I never did quite grasp this concept of always trying to get more horses, either...
    At some point you have enough, at least I do.

    But what I don't get is if they can coax more horses out of the same engine, why not make them more fuel efficient instead?

    I'm not saying they shouldn't make bigger engines for those who want that.
    But it sure would be nice if that 15hp instead of having become 18hp would now simply consume less fuel.
     
  8. Optimum Lawn

    Optimum Lawn LawnSite Member
    Posts: 186

    I just want torque......thats what makes things work when the going gets tough.
    HP who cares...give me torque
    low HP but BIG torque...now we are talking

    Interesting the torque on the Kawy falls off as RPM's increase...but as the load increases and RPM's decrease torque increases....thats good.
     
  9. tacoma200

    tacoma200 LawnSite Fanatic
    Posts: 5,426

    I actually need the power, but much of the work I do isn't typical. Sometimes weekly's are extremely thick in the Spring, and the bi-weeklys are really tough. The 27 on the Lazer feels very weak after running a big block. And the big block looses a few rpms sometimes. But I can go up a long grade with the big block through thick grass and it will gain speed easily if I push the sticks forward. I can't see going back below 29 hp again. Mid 30's would be about right for me with a 60" deck. If I had a fleet of ZTR's I would probably go less on the hp but as the primary worker (mostly solo) I need and want the extra productivity.
     
  10. Lynden-Jeff

    Lynden-Jeff LawnSite Bronze Member
    Posts: 1,405

    Its actually going to be against the law to list HP on machines up here. Has to be CC's as its more accurate.

    Cheers
     

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