Horse Power and its Effectiveness

[Andrew Wakeling]

Hiya All,

I've just got a few theories about horsepower and was wondering if
anybody could comment on them and tell me if I'm actually leading myself
astray.

Right, firstly lets get a few things sorted out.

Power = Mass x Velocity x Acceleration


Ok, so for the guys who like SPEED or velocity, it doesn't mean that a
car producing more horsepower is necessarily going to be quicker than a
car producing less horsepower since horsepower is proportional to mass.
e.g. A small plane maybe very heavy.. I dunno, lets say 20 Tonnes... but
a small car like maybe a Porshe or something could still beat it on a
take-off run, BUT the plane must be producing A LOT of horsepower
compared to the car just because it is a lot of times bigger, and the
engine can cope with that mass. Its speed and acceleration which count.

Ok, Another example but same principle. If you get a car and increase
its Power, than its Velocity or Acceleration must be increased.

SUMMARY of last 2 points: A car which produces MORE horsepower than
another car doesn't necessarily make it faster, but has the ability to
move heavier MASS around.

RIGHT.

Maximum Horsepower and Speed/Acceleration

Ok, If I'm not wrong, I guess most people are looking for SPEED and
ACCELERATION, but I know a few people still like bulky and big cars
which are like Tanks, but just for this conversation, lets say that we
want SPEED and ACCELERATION.

Ok, what is stumping me, is MAXIMUM horsepower and its relation to
Quarter of Mile times. I believe that it has NO direct relation... Ok,
here's my theory.

Firstly we know that Power is the rate of doing Work...

ie. Power = Work / Time

We can see that in the Power formula...

Power = Mass x Velocity x Acceleration

And acceleration is change in velocity over change in time, soo...

Power = Mass x Velocity x (dV/dT)
                          
Right, that all makes sense... but what about the famous dyno graphs
that we all see, and the little pointer saying that it reached MAX
horsepower at some RPM ... etc...
So that means that these calculations must showing the Power at an
instanious time, so JUST because a car is producing MAX horsepower at
some point, how does that indicate its performance over the whole range?
Shouldn't we be comparing the AVERAGE horsepower in the whole dyno run?
It makes logical sense that the car is producing more POWER at a faster
RPM or heavier load, since your making IT work harder and FASTER... but
it takes TIME to hit the maximum horsepower point, so what does it have
to do with the rest of the run???

Ok, here's another example to prove my point... 
If a car was in a quarter of a mile race, and it was working real fine,
and say it started off fine, reached its max horsepower at say the
length of 1/2 the track but then blew the engine and didn't manage to
finish the track... HIGHLY hypothetical OK? But, I mean if you take the
max horsepower, it doesn't MEAN that it was running well, but if you
take the average... you'll find it never REACHED the end of the race... 
SO... 
Average Horsepower = Horsepower / Time

And since Time is infinite, the average was Zero... I'm not sure, but
isn't the area of the graph the total horsepower???

So, is this theory totally wrong? Can somebody argue this or support
this theory?
This was caused by a real life situation below.
Australia Commodore VR... 5.0 Stroked Blown Engine producing 500 HP.
Australia Commodore VS... 5.0 Stroked Blown Engine producing 340 HP.

Both were about the same mass, similiar max boost levels, but totally
different setups, like when the supercharger was most effective, and
stuff like that. Anyway, the 500 HP ended up doing a 15 sec time.. and
the 340 HP was doing 11 secs... So this has got to mean something?

Ok.. One more topic with relation to horsepower...

Horsepower and G-force

Ok, I've heard this to many a time. When you feel the car accelerating,
and you get thrown back into the seat, people say that its horsepower...
But this can't be the case... Ok. Plane example all over again.
If the plane is moving slowing but accelerating... it still would be
producing A LOT of horsepower, and you won't really feel a thing right?
say at about 5 km/h with a 0.1 ms-2 acceleration? ok... Right right...
Next.. A REALLY fast car, can push you a lot deeper into your seat...
Why you ask? Well, its not horsepower, its not torque, and its not the
twilight zone... ITS G-FORCE... 

If you look up G-FORCE in the dictionary, or some fancy science
dictionary, it will say that 1 G (ONE GEE) is when a body is
accelerating at 9.8 ms-2. Ok, thats the same G units in space craft
travel, the same G in the planes and stuff. They say that a human can
only experience about 4 Gs before they start feeling faint since the
blood pools in the body so you don't get enough of it were it counts...
Yeah, your HEAD buddy. Right, before I get too far into this... This
feeling you get which pushes you back into your seat ISN'T horsepower,
its simply G-FORCE, which is the acceleration. You might say that 
if you get more horsepower you get more Gs but that's just misleading...
so get the terminology RIGHT guys.

Ok guys, thanx for listen to me spill my guts, but I thought that I had
to say something since I keep on hearing these things... Its sorta the
same thing with weight and mass, if you know what I mean, and mumbo
jumbo like that just gets us all confused.

Andrew Wakeling.