CC's V.S HP

Discussion in 'Lawn Mowing' started by Bunton Guy, Aug 27, 2005.

  1. Bunton Guy

    Bunton Guy LawnSite Bronze Member
    Posts: 1,746

    Im in the market for a 72" diesel mower to get a total of 3 large properties done (80+ Acres) I did some research on
    Exmark: (same as toro ) 27 hp Diahatsu - 952cc's
    Dixie Chopper: Yanmar 50hp turbo diesel - 1496cc's
    Hustler: (same as ferris) 34hp CAT diesel - 1490cc's

    My obvious 2 that im interested in are the CAT & Yanmar...both having almost the same cc's but 2 way different HP ratings. How does this level out? I only have tq. #'s for the CAT diesel and that is at 70.8
     
  2. topsites

    topsites LawnSite Fanatic
    Posts: 21,654

    Only thing I can think of is the higher-HP motor has much better compression, it's the same thing with my bmw 318is it only has an 1800cc motor but it's a LOT more powerful than say, the Volkswagen Golf with the 1.8 litre.

    Other things make a difference are spark-to-plug delivery methods, perhaps one mower has the stronger ignition coil / better wires... Then air-flow makes a few percent of it as well, one just has more performance than the other and SHOULD be more expensive (price the motors by themselves if you can and see if the 50hp isn't more expensive than the 34hp, it should be).
     
  3. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    Diesels don't usually have spark plugs, coil or wires.

    Torque and horsepower work together to get a specific job done whether it be cutting grass of hauling a 80,000 pound trailer.

    Think of horsepower and torque this way.

    You have a mower that will cut grass really fast until you put a load on it. Then you have to slow the mower down just so you don't kill the engine. That's a engine with high horsepower but low torque. It's kinda like an import 4 cylinder car. It's really fast but only because the car is lightweight. Put some weight on the car and it turns into a turd.

    On the other hand you have a mower that will literally cut through tree trunks but it won't go very fast. That's a high torque engine. It's like a tractor trailer. It'll pull a ton but it won't do it very fast (especially uphill).

    A great mower will have both horsepower and torque. Granted there are a ton of other factors like deck design, wheel pumps and motors sizes, pulley sizes etc. but if you don't have a balanced engine to begin with you're screwed from the very start.
     
  4. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    Very good analogy, I couldn't have said it better myself.
    As for the HP to CC issue. it is going to be a ongoing problem over the next few years as most major manufactures start to change from the American HP to the metric Cubic Centimeter. Took a trip to Germany this spring. Talked to a Park supervior when we were at one of their larger parks. They were mowing and went to get a look at their set up, especially since they have very small trucks. He had an interesting mower kind of a cross between a lazer z and a Grass hopper. I had asked him what hp his mower was and he was quite confused. When all said and done it was a 600 and some change CC engine.
    Briggs has had a few problems with their stated HP. Thus why you see more of the small engines with out the HP rating on them.
     
  5. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Posts: 2,697

    Perhaps they are measuring their HP at different RPM's.
     
  6. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    Cant go wrong with the CAT imo. Most of the yanmar's additional hp is from the turbo.
     
  7. KillaWhale

    KillaWhale LawnSite Member
    Posts: 62

    Is the Yanmar a turbo diesel? If not there is you HP diference. Just to add, diesel do not have spark plugs. They use fuel pressure and compression to ignite fuel. I agree with Bunton guy about the CAT, if they only made a mini cummins :D
     
  8. Brianslawn

    Brianslawn LawnSite Silver Member
    Posts: 2,004

    the cc is the size of the engines displacement. turbo add to the HP. those fast imports with high HP on little 4 bangers is because of the turbos and coolers. i dont got much experience with those mowers, but the ferris IS would probably be the fastest and smoothest ride. i dont ever here any complaints on cat's either.
     
  9. Twigs

    Twigs LawnSite Member
    Posts: 15

    Torque is measured, horsepower is calculated. You hook up the motor to a dyno and measure the torque. You calculate horsepower with the formula: (torque X rpm) divided by the constant 5252. So, at 5252 rpm, torque and horsepower are equal. If your motor operates, generally, below 5252 rpm, torque will be the major consideration in power. As operating rpm approaches 5252, and exceeds 5252 rpm, horsepower is more of a consideration in performance. If an engine doesn't measure much torque, you got to spin it a lot above 5252 rpm to make meaningful power. Look at the small displacement Japanese motorcycle motors (1000 cc) turning 14,000 rpm and making little power at low rpm, but gobs of power (165 HP) at high rpm. They want power and low weight (hence light engine components), so they got to "spin em." In a low rpm motor (most diesels) torque is really all that is important. Horsepower numbers associated with a low rpm motor are for advertising and marketing. With a higher rpm motor (most small displacement gassers) horsepower is more relevant. You got to spin it above well above 5252 rpm to use the low measured torque to calculate (and create) the high horsepower rating. While a perfect world would have engines with ultra high torque, high operating rpm, and therefore (because of the calculations) ultra high horsepower, such is virtually impossible, because high torque is the result of lots of displacement (cubic inches or cc's). Big, heavy components don't like to spin fast. But, with high torque, you can have great power at low rpm resulting in long engine life. Weight is usually the biggest negative with high torque engines. Gas engines are a compromise of components' weight and rpm. BIG! Big Is Good!! Go Cat Go!!
     
  10. CuttingCrew

    CuttingCrew LawnSite Member
    Posts: 193

    Well said Twigs.

    Mike
     

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