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For maximum accel in a car....

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Old 05-14-2003, 06:19 PM
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Default For maximum accel in a car....

When is the best time to shift?

Top of the powerband
Redline
right before the revlimiter kicks in
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Old 05-14-2003, 06:42 PM
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Theoretically and in practice, you should upshift so that the drop in rpms will bring you back down to the torque peak of the motor. So you just need to know the torque peak and know how much each gear shift slows the engine. This is assuming you have the traction to do so. Once youve been driving for a while, you can just feel it after a few laps. (i used to drive tracks a lot).......
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Old 05-15-2003, 12:25 AM
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On my drag car i shift 500 rpm above peak hp, on the nos i shift about 300 below . on a solid roller cam. This gets the best et i have found . as long as you dont float the valves.
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Old 05-15-2003, 02:17 AM
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You need a dyno graph and need to know how much rpm you drop in each gear change. You plan each shift so that rpm you will cover in that gear gives you the highest average horsepower over the rpm range. Knowing that, you will end up shifting from 1st to second well beyond the peak horspower rpm because of the large drop in rpm when you hit second. The 3 to 4 gear change will happen much closer to peak horepower as the drop in RPM is less. This is why you see mutiple shift lights for each gear change in many cars. On the bikes, we have a gear position sensor that activates the shift light at differnt rpm's for each gear.

Now another thing to conside is the time it takes you to react to a shift light. On my streetbike for instance, by the time I react to the shift light to hit 2nd gear, I have already gone well past the rpm where it was activated because the bike is accelerating so hard (0-60 in about 2 seconds and thats all first gear). During the 4-5 shift, the bike isnt accelerating as hard so I'm shifting much closer to the light coming on.

Again, this can all be done on a chassis dyno with a full pull through the gears. You can set your shift point and see on the graph exactly where you were shifting each gear.

Now if your talking about dads car, find out where it makes peak horsepower and just ran past that a bit to keep it in the meat of the power curve.
 
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Old 05-15-2003, 06:38 AM
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It would be easy to to help if you had a dyno sheet and what ratio each gear is.
I learned by the seat of my pants. The tach was in the dash but I never looked at it. Was too busy driving so I shifted by ear. Must've gotten it right because the only races I lost were to guys with bigger engines and even ran door to door with some of those.
It was always fun to keep up with a 383 or 396 when all I had was a 289.
340's, 350's, 351's never stood a chance.
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