Tom,
Your engine builder friend illustrates an example where torque data can be
very useful. "I have a friend who puts motors together for Shelby. His
comment to me was that a certain bore/stroke configuration (displacement)
will only put out a specific amount of torque." I've also heard it said that
engine builders tend to look at the torque curves instead of the horsepower
curves, and it's for the reason your friend expresses. If about the best one
can do with a 289 is, say, 300 lb-ft of torque, then it makes sense to see
how close you are coming to this ultimate limit across the rpm range. On the
other hand, for those of us who use the engines, basing a decision on torque
will invariably lead to a bad decision, for example, in terms of gearing or
selecting shift points. A good example of this was given to me by one of our
San Diego Tiger owners. Perhaps some of you have also heard the rule of
thumb that you should shift at the point where the horsepower and torque
curves cross. Since HP=T*rpm/5252, HP and torque curves ALWAYS cross at 5252
rpm, so this is obviously erroneous advice. As Theo and I have been saying,
shifting should maximize the area under the HP curve. Forget the torque
curve, just look at your HP curve and figure your shift points accordingly.
The same philosophy should guide your selection of rear end and transmission
gears. - that is of course, if it's performance you are after. Now, if you
want to increase gas mileage and decrease noise, that obviously dictates
other choices. For most of us who mostly drive our cars on the street, some
kind of a compromise must be reached.
Bob Palmer
rpalmer@ucsd.edu
rpalmerbob@adelphia.net
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