Stop in for a cup of coffee
So, there is huge confusion across all boards. Increasing vs decreasing IAB and MAB. Which makes them come in sooner and richer? I see an article where Steve Brule leaned out a 2500rpm rich condition of 12.5 afr by going from a 0.069 IAB to a 0.076. So increasing the bleed leaned it out to a 13.5 afr. Then a larger MAB leaned out the top end 0.041 to 0.045. Made power. Then from 0.045 to 0.035 which richen it back up. Lost power. But, there are huge arguments even on RFS page.
Matt, is this how you understand the circuit?
I'm just too overwhelmed with stuff, but sounds like things have gone downhill at RFS.
When there is a radical change like those just described, like .069 to .076" diameter, then we learn very little.
Something was way off in at least one of the tsts, or maybe both.
On a properly set up carb, small changes in airbleeds should produce a predictable change in fuel.
When a little bit of air is introduced to a circuit and mixes in as tiny bubbles the mixture has less density than plain fuel. It is lighter and flows quicker. It passes through restrictions downstream more easily. These are reasons why in some situations there can be more fuel flow with increasing air bleed.
When the bleed is too big then the air is no longer tiny bubble but big bubbles. These bubbles can join together to make large bubbles of air between the fuel. Then its totally unpredictable but likley will spurt unevenly.
Another factor is the fuel restriction and air bled in can't be going from laminar flow to turbulent flow. Again everything becomes unpredictable then.
This is why the old Holley's (and Carters etc) are usually the best references to work from. When carbs had to work consistantly for production vehicles, the holes were in the positions and sizes that I call the working range. We can step those up or down a little and not get wacky results.
my .02