[DMCForum] Horsepower Defined For Jim
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[DMCForum] Horsepower Defined For Jim



Most laypeople when they hear the word "horsepower" envision a team of
horses pulling a wagon -- 300 horsepower = 300 horses hooked together
charging across the prarie. That's altogether the wrong vision: they
should envision one horse hooked to an old wooden gear turning it in a
circle (which is where the calculation came from in the 1800's BTW).
Horsepower is how many revolutions that horse could make within a
certain time. Or another way to look at it would be the length of time
necessary for that horse to make a certain number of revolutions.
Translated into car terms, it is the ability of an engine to rotate
itself. A higher horsepower engine can rev higher, and do so faster,
than one with less horsepower.

Notice we haven't mentioned what KIND of horse this is -- is it a big
strong Clydesdale or a little circus pony? Makes a big difference in
what rotating that wheel actually accomplishes. That's torque: the
amount of power created by turning something, like a crankshaft. A
higher torque engine can exert more force on the drive train with each
revolution than a lower torque one.

Horsepower is important because it measures the RPMs through which an
engine is effectively producing power, and how quickly it gets there.
Torque is important because it measures how much power is actually
being produced by those RPMs.

My 460's are high torque gasoline engines. Low compression produces
425 lbs. I believe high compression (I have one of those too) is
450-475. Each revolution translates a lot of power to the wheels. But
the effective RPM range in which this is possible is rather small.
Maximum torque is produced at 2500 RPM, and drops off sharply
thereafter. By 4000 it's off the bottom of the charts. I may only have
210 horsepower (low compression), but can accelerate 0-60 effortlessly
because the engine never leaves its power band (the neighborhood of
2500 RPM). If I were to force the car into 1st gear and try the same,
0-60 would take much longer, and by the time the engine reached high
RPMs all it would be making is noise (a LITTLE power would still be
produced of course, but certainly nothing like it was making several
thousand RPMs ago).

Bill Robertson
#5939

>--- In DMCForum@xxxxxxxxxxxxxxx, Jim Strickland <ihaveanaccount@xxxx>
wrote:
> i would call horsepower the true measure of an engine's power.
hence the
> name horsepower. 
>
> I don't know which vehicles you are referring to whose "power band was
> left behind several thousand RPM's" before the redline. 
>
> The peakiest high rev production engine (honda f20c) has peak power at
> 8300rpm, redline at 9100rpm.   = 800rpm.
> the honda b18c peaks is at 8000, redline at 8400rpm = 400rpm.
>
> Are you saying 400rpm above peak power isn't in the power band?
>
> maybe you should give specific examples about engines you are talking
> about.
>
> Jim
>
>
> On Wed, 07 Jan 2004 05:29:45 -0000 "content22207"
> <brobertson@xxxx> writes:
>
> > You're so strung out on HP that I wonder where you think torque --
> > the
> > true measure of engine power -- fits in. It's like all this
> > red-lining
> > nonsense: what good is pushing an engine to its breaking point if
> > the
> > power band was left behind several thousand RPM's ago. Yes, HP will
> > get that old crankshaft spinning. But if doesn't have any power in
> > it,
> > all you've succeeded in making is noise.
> >
> > Bill Robertson
> > #5939
> >
> > >--- In DMCForum@xxxxxxxxxxxxxxx, Jim Strickland
> > <ihaveanaccount@xxxx>
> > wrote:
> > > > Jim Strickland (who enlisted Martin to back him up) claims that
> > > > advancing ignition time ALWAYS leads to increased HP, and that
> > the
> > > > ideal point of spark is at the threshhold of detonation. I
> > couldn't
> > > > disagree more.
> > >
> > > yes, i am paying him to agree with me.  If you agree with me too i
> > will
> > > pay you.  Just agree that lowering compression increases
> > horsepower and
> > > your trip to the darkside will be complete.  I never said that
> > advancing
> > > will always lead to HP increase, though i will say that advancing
> > (until
> > > knocking!) will in most if not all cases lead to higher PEAK
> > horsepower.
> > >
> > >
> > > > The reason I mentioned Martin by name was because he recently
> > > > referenced a URL (on the List) that supports MY assertion:
> > advancing
> > > > ignition time does not necessarily lead to increased HP. I was
> > > > amazed,
> > > > after the thorough drumming I received over that very issue,
> > that he
> > > > then referenced an online article that claims I was correct in
> > the
> > > > first place!
> > >
> > > Ah, so you don't agree with my interpretation of martin's website?
> >
> > > Interesting that you won't comment on it, but continue to claim
> > that you
> > > are correct.  message 9744.  It basically says that you
> > misinterpreted
> > > what was on the site and are still wrong. ;(
> > >
> > > > Just so everyone's clear: I have Lincoln Mark V's from 1977 and
> > 1978
> > > > with 460 inch engines. The engines and distributor bodies are
> > > > identical -- look them up in the big NAPA engine master book.
> > The
> > > > only difference between these two years is specified base
> > ignition
> > > time:
> > > > 13 degrees BTDC in 1977 and 16 degrees BTDC in 1978. In this one
> >
> > > > instance at least, advancing the spark LOWERED published HP
> > (from 212
> > > to 210
> > > > if I'm remembering correctly).
> > > > Advancing ignition time does not ALWAYS lead to more HP.
> > >
> > > Is this at idle or at peak hp?
> > >
> > > Jim
> > >
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>
>
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