[Shotimes] Dyno charts

[Ron Porter]

I agree with your final conclusion, but I don't agree that the amount of
horsepower is "most important"

In reality, horsepower doesn't exist. It is a math formula to show how much
work is done over time. Torque is a real force, and the horsepower
calculation shows how much work that torque can do.

Let's look at Ransom's example: a lawnmower producing 220 HP at 150K rpm, or
a SHO motor producing 220 HP at 6K rpm. They technically producing the same
amount of work at their peaks, but engines don't only run at their power
peaks.

Another example is a 240 HP GTP versus either a 220 or 235 HP ATX SHO.
"Only" 5 hp (over the Gen 3), but vastly different performance
characteristics. Another example was the revised Mustang GT 4.6 motor going
into '99. "Only" 35 more HP, but they pumped up the torque curve throughout
the entire rpm range, and the car lost over a second in the quarter-mile,
leading to accusations of "sandbagging" by dimbulbs who don't understand how
engines work.

The gross amount of HP at the peak can be misleading and not represent how a
car actually runs. Putting aside gearing, weight, etc, just having higher
peak HP will not give you a quicker/faster car.

Ron Porter

-----Original Message-----
From: shotimes-admin@autox.team.net
[mailto:shotimes-admin@autox.team.net]On Behalf Of BJamesjr@aol.com
Sent: Wednesday, January 15, 2003 11:16 PM
To: shotimes@autox.team.net
Subject: Re: [Shotimes] Dyno charts


> Thats not to say it won't accellerate, though. Think about the potential
in
> all that rotational weight spinning at 150,000rpm.

Understanding these 2 terms can be difficult, but horsepower is what it
says,
power.  The amount of horsepower is what is most important.  Secondarily is
at what engine speed the peak horsepower occurs.  This tells you what
gearing
and shift points you need to extract the horsepower.  For instance a
Corvette
redlines at a comparatively low rpm whereas a Honda S2000 redlines at a
relatively high rpm.  For quarter mile runs you would want different gearing
for one vs. the other.  For street performance you obviously have to operate
the Honda at higher rpm's for similar performance.

OK, what about torque.  Torque is the measure of twisting force.  This is
already figured into the horsepower rating.  Knowing the peak torque rating
does tell you something though.  For instance look at the rpm at which peak
torque occurs vs. the rpm at which peak horsepower occurs and you can
determine how wide the torque band of the engine is.  That is, 2 engines
with
similar peak horsepower ratings might actually perform differently if one
has
a wider torque band than the other.  But what about the torque number
itself?
 You can look at the peak torque for a diesel engine and it will be a pretty
big number, as compared with a high rpm engine like an SHO engine.  So you
put that diesel in gear and try to accellerate but you don't get much
because
to put that torque at low rpm to the ground you need to be in a fairly high
gear.  If you want to lug the engine around town, pull a trailer, etc. then
having the peak torque near the range at which the engine will operate is
good.

Net result- both horsepower and torque numbers are important depending on
how
the engine will be used.
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