Usable Horse power

Discussion in 'eXmark' started by Vibe Ray, Dec 4, 2002.

  1. Vibe Ray

    Vibe Ray LawnSite Senior Member
    Posts: 785

    I just read the post about the 28HP EFI and you commented on "usable HP". I was just wonderin' if you could jot down the usable HP specs for some of the popular engines your units come with? Is there ever a time when a lower labeled HP motor has more usable HP (for our applications) than a higher labeled HP motor? Thanx!
     
  2. Brieldo

    Brieldo LawnSite Member
    Posts: 192

    Well...John Deere always rates their stuff in terms of both flywheel horsepower and also in PTO horsepower. It's usually 2 HP less than what's at the flywheel... Perhasp this applies to most situations. I think it also depends on how the power is being applied to the deck...
     
  3. eXmark

    eXmark Manufacturer / Sponsor
    Posts: 4,258

    Vibe,

    Thanks for the question.

    Useable horsepower is actual power available for use. It's sort of like gross horsepower vs. net horsepower. In 1971 the engine manufacturers went from using a gross rating to a net rating. Gross was an engine with now power steering pump, no alternator, no air filter and no muffler. Net horsepower is tested with all of these items in place.

    The 26 EFI as an example is only rated at 1 hp more than the 25 hp Kohler. LetÂ’s assume that both of these are gross numbers (they may be net) and no exhaust or air filter were in place. When you put all of these back on the engines the 26 still has 1 more horse power and that is where it's rated.

    Now you take that same 26 efi engine and you add a low restriction canister air filter, clean flowing muffler, some changes to engine rpm and the governor and you get an additional 1 hp. You've now got an engine that while rated at 26 hp by Kohler actually produces 2 more horsepower than the 25 hp engine. That is 2 more useable horsepower on an engine that has a decal only showing 1 extra horsepower.

    The nice thing about this instance of 2 extra useable power is ALL of it goes to the mower deck. The hydros aren't going to use any more power than they ever did. In this case 2 useable horsepower feels and performs like a lot more power.

    Thanks

    Terry
     
  4. Vibe Ray

    Vibe Ray LawnSite Senior Member
    Posts: 785

    I got it....so which engines have the most usable HP and which have the biggest difference between usable vs. labeled HP among the engines that exmark uses?
     
  5. eXmark

    eXmark Manufacturer / Sponsor
    Posts: 4,258

    Vibe,

    The highest useable horsepower engine we offer is the 31-hp Daihatsu gas. The 27 hp Daihatsu, 27 hp Kawi and 26 EFI all are fairly equal in terms of useable power but each could claim an advantage at a given rpm.

    We don't really have any ratings for useable horsepower. The 26 EFI is really the exception to the rule. Most engines have actual working power similar to their horsepower rating. The EFI just gives you more than is advertised.

    Thanks

    Terry
     

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