[AT] Horsepower Question

[Ken Knierim]

Horsepower is related to engine speed (revs) and torque. The tractor engine
makes horsepower at much lower speeds with correspondingly higher torque.
The smaller engine may put out a peak of 20 HP at the RPM peak but as soon
as you lug it down and compare useful horsepower, you'll find a big
difference. And the smaller engine isn't as likely to survive day after day
of full power usage like a tractor engine and in most garden tractors, it
never has to... also I believe the 20 HP from the tractor is actual usable
horsepower at the drawbar and the garden tractor rates it at the engine
before drivetrain losses.

Hope this helps.

Ken in AZ

On Wed, Oct 6, 2010 at 6:00 AM, Ben Wagner <supera1948 at gmail.com> wrote:

>  Here is a puzzler that maybe someone with a better knowledge of
> engines can answer.   I was asked this question, and had to announce
> that I needed to look it up.  What better place than the AT Mailing?
>
> I have a Super A with four cylinders, producing c. 20 HP.
>
> I have a lawnmower, with an engine that says it is also 20 HP, with only
> two cylinders.
>
> What is going on?  Is this two different measures of HP?  Or has
> technology improved that much?   What makes a little two cylinder "small
> engine" have the same HP as four cylinder "tractor" engine.
>
> Thanks,
> Ben Wagner
>
>
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