Just to throw water on the simmering missives:
Talk about speaking at cross purposes. Break out the Mechanical
Engineering textbooks, and lets all talk the same issue.
We have owners, who are knowledgeable about practical mechanical
relationships, talking about "torque" and "horsepower" as if they were
independent quantities. They are not, but rather very dependent
quantities, the ONLY variable being the RPM that's being investigated,
and perhaps the throttle position if talking about "potential
increase". They are being answered by responses that rely upon
engineering definitions. Having differing views on the relationship of
the variables, there are bound to be misunderstandings.
On "Horsepower", "Torque", and "RPM":
The only time they are "independent" is when you are at one set RPM, in
a cruise mode, and decide to change the rpm. Then you will absolutely
follow the engine design potential ("torque curve)" as the RPM changes.
This is sometimes confusing to those not familiar with the origin and
definition of these terms.
If one were more familiar with electricity, it would be like arguing
whether amps or volts has the most influence over power (watts). They
are only dependent variables in the defining equation E = I x R (or
Volts = Current x Resistance) and P = I x V (Power = Current x Volts).
Arguing whether it is current (I) or volts (V) that produces power (P)
obviously does not make sense here. They are independent variable that
DEFINE power. Note that Power is also = I^2 x R by simple math
substitution of the defining terms. No slight of hand.
Horsepower = (N x T) / 33,000 (unit adjusting constant).
The N is the rpm at which you want the information on the horsepower
being generated, the T is the dyno measured torque the engine produces
at full throttle when the external load drags the RPM down to the level
being considered. If an engine is dyno tested 500 rpm increments, and
the load increased to maximum the engine can stay at each rpm level at
full throttle, you can get those pretty curves you see on the Edelbrock
site.
Many dyno houses do NOT do this, but get the maximum horsepower of the
design. Less work and strain.
It is the engine design that dictates the torque curve, hence the
maximum torque/rpm relationship that DEFINES the horsepower/rpm values.
It is just confusing to hop back and forth between different engine
designs (torque curves) and try to compare one to another at a given
rpm. They are not the same engine, and the results are only meaningful
when like is compared to like. It is not intuitively obvious to one
not familiar with the interrelationships between these parameters, and
how they are determined, that get confused when one independent variable
is compared to one from a different design. You need ALL the design
parameters to make a comparison.
Although these are very simple mathematical terms, those not familiar
with their derivation and interrelationship, or the mathematics
involved, can get misled by making comparisons between apples and
oranges by comparing fruit diameter, or acidity.
There are plenty of technical discussion that can be located by
"Google", if not Marks Handbook of Engineering and Physics.
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Steve Laifman
Editor
http://www.TigersUnited.com
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