Fine Tuning a 360 Magnum with a Brawler "Double Pumper"
So smaller MAB is a slower, richer booster and larger MAB is faster and leaner essentially?
No, the MAB affects both ends of the fuel curve differently.
At low air flow, the MAB acts like an emulsion hole. The smaller air bleed, with its smaller hole lets less air into the main well so the fuel column is heavier and harder to move to the boosters at low air flow. So the booster starts later.
At high air flow, the same thing happens. The smaller MAB bleeds off less signal so the fuel curve gets richer.
A bigger MAB at lower air flows is letting more air into the main well so the fuel column in the main well is lighter and it starts the booster sooner. At higher air flow, the bigger MAB bleeds off more signal so the fuel curve gets leaner.
Smaller MAB is leaner at low air flow because the booster starts later. The smaller MAB is richer at high air flow because the smaller bleed doesnt “bleed” off the signal.
The bigger main air bleed does the opposite.
You are affecting both ends of the fuel curve by changing MAB’s. The thing to remember is whatever the MAB does at high air flow it does the opposite at low air flow.
Starting the booster sooner makes the fuel curve richer at low air flow. Starting the booster later makes the fuel curve leaner at low air flow.
Most guys use a MAB that is way too big. That starts the booster sooner. Since you are now on the booster and it’s rich, guys start delaying the opening of the power valve.
That makes its own mess.
It also makes the fuel curve richer because the T slot is still delivering fuel.
And the big MAB is now even richer down low.