What kind of air density change will trigger a change in carb setup for the LO206? If I set my carb up right for 90% dry air density but later this year spikes to 95% or 100% should the carb settings be changed?
Absolutely.
1% change in A/D requires a 1% change in fuel. Air quality goes up, fuel needs to go up proportionally.
In the real world, moving the clip down (richer) on the needle 1 notch is pretty much equivalent to going up 1 jet size.
Most times, that requires a 5% change on your A/D gauge before any action is needed. Also depends slightly on your altitude and humidity, but that'll get you close. That's assuming that your carb was tuned correctly on the dyno to begin with.
An A/F Ratio gauge, or O2 sensor, is even more accurate (in my opinion), but slightly more difficult to use considering you cannot use it during actual racing (ie only for practice.)
Bottom line, if it's faster on the stop watch (or Mychron) run it.
I've seen engines that were tuned terribly wrong still make it into the tech barn at the end of the day.
