Originally Posted by
Brian Ratliff
There is definitely a formula. Usually it is obtained by a test at 2-3 minutes and another test at 15-20 minutes. A curve is fit though those two points which can tell you an estimate for critical power at other time intervals. Unfortunately, I can't tell you the equation off the top of my head, but it should be in any number of training books. I believe it is listed in Friel's book, though I am not sure.
Originally Posted by
SpongeDad
it turns out the published power curve is not that accurate when I benchmark against my PT..
See SpongeDad.
Two data points to do a CP curve is pretty light if you're looking for real accuracy. Best measure of various CP's is obtained by shoving all your data files into a custom WKO periodic and setting the dates you want to get data from. Even that presumes you have hit max at the different CP numbers. If you've got a lot of race/TT/test data you can usually get a pretty good handle on this.