On Sun, 11 Oct 2009 15:05:34 -0400, wrote:

On Sat, 10 Oct 2009 22:28:39 -0400, wrote:

On Sat, 10 Oct 2009 19:36:45 -0400, wrote:

On Sat, 10 Oct 2009 11:19:38 -0400, wrote:

On Sat, 10 Oct 2009 11:01:54 -0400, "Ed Pawlowski"
wrote:


"Worn Out Retread" wrote in message
...
I am looking for a new snow blower and have discovered that the power
rating of the engines are no longer in "Horse Power" but in "Foot Pounds"
if given at all. Sometimes all that is given is the CC's of the engine.

Even the people selling these machines don't know what the "Horse Power"
ratings are so that old geezers like myself can understand what is going
on. Does anyone have any general rules regarding the conversion of Foot
Pounds or CC's to Horse Power?

Horsepower to CC is highly variable and not a good measure of power. My
cars have different engines. The 3800 cc is 190 HP but my 3300 cc is 234
HP. I suspect smaller engines are similar.


For the types of engines generally found on lawn equipment, comparison
of new engines and old engines of same brand and displacement is a
valid comparison. These are utility engines designed to run at optimum
RPM's while in use. A car engines is vastly different in it's
requirements.

If an old snowthrower with a 13 hp Briggs engine is 350cc, then a new
350cc Briggs powered snow blower will be about the same HP.
Unless the old 350cc 13hp Briggs is a "side valve" engine with 5.6:1
compression ratio, and the new 350cc engine is an overhead valve
engine with 11.5:1 compression ratio - which MIGHT be a 18HP engine.

Numbers just picked out of thin air, but the principal is there.

The principle is pretty gaseous as well. In the real world, the old
and new 350 cc engines will have about the same HP. Seen any snow
blowers with Briggs or Tecumseh engines that call for premium gas
lately? Ever?


You are blowing smoke. Because you don't know anything about engines.
My numbers were a bit high. A 20HP Intek is 8.8:1. A 25 HP Kohler
Command is 9:1, and the Briggs Animal runs 9.5, 9.7, or 10.0 :1
depending on class.


From Popular Hot Rod's tech pages:

Basics
Increasing the CR produces an increase in output throughout the rpm
range. It is also worth an increase in fuel economy. If a longer
duration cam is installed, raising the CR at the same time can be
worth even greater dividends than these two moves considered
separately. When the CR is raised, peak combustion pressures are
increased. As a rough rule of thumb, cylinder pressures are about 100
times what the CR is so, from a 10:1 engine, we would expect to see
about 1,000 psi of peak combustion pressure.

Cylinder pressures and output will increase as the CR is raised, but
what is less obvious is that the increase in compression also
increases the engines thermal efficiency. Thermal efficiency is a
measure of how effectively the engine converts heat into mechanical
power. To appreciate this it is better to consider the engines
expansion ratio (ER). This is the opposite side of the coin to the CR
and describes what is occurring as the piston moves down on the power
stroke rather than what happens as it moves up on the compression
stroke.


You are an idiot, Clare. Obviously I understand that engines can and
are built for different types of performance and different uses. We
are talking about SNOW ****ING BLOWERS, dimwit. They aren't high
performance racing machines. You could even know the horsepower of a
given displacement Briggs snowblower by knowing the horsepower of a 15
year old Tecumseh Snow blower engine of the same displacement. It
would be quite similar.

Popular Hot Rod! Bwhahahahaha!