I've got a discussion on shift points on my website including some graphical demonstrations. It can really help you decipher what's going on. To really do it effectively though you need to do a Max says and visit the dyno. There is really no way to wisely choose it without knowing the HP/TQ trends of your car. In fact, one shift point really isn't enough. You need different shift points for each gear to really get the most out of your car. Most of us are limited to single shift lites, unless you've bought one of the more expensive tachometer/lite combinations.
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Jeff Chambers
Trophy Stock #3
11.97 Seconds / 114.5 MPH
Chambers Racing Team