Originally Posted by vinniekq2
ap72 what you are saying is basically correct for a street car.If the car is tuned(example only) for a fuel /air ratio of 13:1 at W.O.T. and the engine keeps this ratio all the way through the rpm range then that car will be fun to drive and will perform the same at the track,just dial an et and have fun.
If you want to go faster a track tune will be 12:1 all the way through the rpm range and it will go quicker.If you decide that at the track you are a true racer and you uncork your exhaust system,then that tune needs to be 12:1 with open exhaust and that will go quicker than the above 2 tunes.
Why would you tune your carb to have 12:1 at part throttle? A well tuned carb can have a perfect cruise AFR (15:1ish) AND a perfect WOT afr (12.8:1ish). Uncorking a restrictive exhaust can affect WOT AFR a little- but your problem there is the exhaust, not the carb. In most cases where you have a good exhaust the difference in AFR between open exhaust and connected is very little.