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## Re: When to shift?

 To: Bob Palmer Re: When to shift? Larry Paulick Thu, 22 Feb 2001 09:39:00 -0500
 ```If I remember, Jim B has a GMeter, and was happy once he found a way to secure the meter to the windshield. Jim, have you or others on the list used this device to tune your car, or practice skills in launching your car. It seams like a reasonable way to do both, after the whole package is together, and fine tuning is in order. I had my car dyno tuned, and believe it is one of the best performance expenses, but the GMeter is real world, with you driving your car, and as many practices as you or your tires can take. Larry Bob Palmer wrote: > > Stu, > > 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 > > TTFN, > > Bob > > -----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. > > Stu ```
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