Single or Twin?


Old 03-22-09, 06:58 PM
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Single or Twin?

I am in the market for a lawn tractor for my dad. I am looking for a full pressurize oil system. I prefer a Kohler, but would go with a B&S depending on price, size, etc. Deck size 40-42", Non-Hydro, 15-20 hp.
Question is which would use less gas, single or twin? This is used only for mowing. He has just enough of an incline to warrant the pressure lube system. When I was snowmobiling, a 340cc twin used less gas than 340cc single. (it didn't have to work as hard). Not sure how lawn tractors are affected.
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Old 03-22-09, 07:21 PM
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Hmmm, That's a good question Indy....

I never checked APG on a mower before, But it does seem a twin would have to work less, But grass height would play a part as well.
Old 03-22-09, 08:08 PM
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The combustion efficiency is considered better the more cylinders you have, given the same displacement of the engine. The idea behind it is the fuel air sits in closer proximity to the flame front origin which becomes a factor in complete combustion. The other things that come into play are the amount of time for the burn to occur and the distance the flame front has to travel. I don't know if that is fact or theory.

It could all be true, but it's hard to compare when displacement and horsepower increases along with the number of cylinders.

I would have to wonder how the stroke of the engine comes into play, too. Long stroke engines in a single would have to be better luggers than a short stroke twin.
Old 03-23-09, 08:17 AM
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Grass height is not a problem as it would not get too high.
Remembering back to my days in college, I rememeber that the longer the stroke, the more power(torque) you get and the closer to square (bore & stroke the same) the better the gas mileage. And if you have a small bore, long stroke you get both.
B&S 20hp twin INTEK-540cc-3.7" bore x 3.06" stroke
B&S 19.5 single INTEK 500cc -3.56" bore x 3.06" stroke

Kohler Courage 20hp twin-725cc-3.3" bore x 2.6 stroke 38.4 ft lbs torque.
Kohler Courage 20 hp single-597cc-3.7" bore x 3.4" stroke 36.9 ft. lbs. torque.

I find it strange that B&S rates their push lawnmower engines in torque, not hp. Yet on the intek engines, they won't tell you the torque.

Last edited by indypower; 03-23-09 at 09:55 AM.

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