[Top] [All Lists]

RE: When to shift?

To: "Stuart Brennan" <sbrennan@ncounty.net>, <tigers@autox.team.net>
Subject: RE: When to shift?
From: "Bob Palmer" <rpalmer@ucsd.edu>
Date: Wed, 21 Feb 2001 22:25:32 -0800

I too believe in confirming theory with experiment. Actually, if you think
about it, a chassis dyno does about the same thing you are suggesting. Some
work different than others, but a lot of them calculate horsepower by
accelerating the rotating mass with the rear wheels. Pretty equivalent to
accelerating the mass of the car. If you do the G-meter tests, we can easily
calculate the horsepower curve. We do need to know the speed of the car and
it's mass. BTW, one of the guys that runs a dyno here in San Diego thinks
torque is "real" and horsepower is just "theoretical", because you have to
multiply torque times rpm to get horsepower. But just minute here; torque is
force times distance, so I guess it's all just a mirage!! Maybe I'll start a
new fad by talking about the down "force" of the pistons as being what
"really counts", or come to think of it maybe it's really the compression
pressure in the cylinder times the piston area that produces the down force,
that creates the torque that produces the power that's really important.
It's all so very confusing!!! Maybe Chris Vaught's Zen approach to drag
racing is more satisfying. Of course, he may be at a bit of a disadvantage
in a car he has never practiced his meditations in. You probably wouldn't
last long as a NASCAR or CART driver with that attitude either. I'm pretty
sure with a $100k motor, they don't want you using the seat of your pants to
decide when to shift - just guessing, but if it was MY race car I'd want
details like that nailed down pretty tight.

When the green flag drops, the b.s. stops



-----Original Message-----
From: owner-tigers@autox.team.net [mailto:owner-tigers@autox.team.net]On
Behalf Of Stuart Brennan
Sent: Wednesday, February 21, 2001 9:33 AM
To: tigers@autox.team.net
Subject: When to shift?

Torque curves?  Horespower curves?  Red line?  Hmmmm....

If you really think about it, you should shift either when the engine is
about ready to explode, OR when the next gear up would give you more
accelleration, as in when an engine runs out of breath at high revs.  I
would say that you should use a "G-Analyist" or whatever that thing was
called, to plot your accelleration vs speed for each gear, idle to red line.
Overlay these plots, and it should become obvious where to shift.  This way
you would not have to compensate for any other factors.  You are directly
measuring the result that you want.


<Prev in Thread] Current Thread [Next in Thread>