J
Jack Klarich
Guest
Good info and makes sense:sThere is always a pressure drop across the air filter. The better the filter flows, the less the pressure drop. This pressure drop causes a slight vacuum, pulling in more gas. Put on a higher flow filter, and you reduce the pressure drop and vacuum, pulling in more air and less fuel. This is why you can run leaner with higher flow air filter.
Since most exhause is IR(Individual runner) and not a shared system, reversion can also make a difference in what the cylinder sees. And since both intake and exhaust valves are open at the same time during overlap, the carb can actually "feel" the pulses from the exhaust, and this too can change jetting requirements.
(In my racing days I've cured backfiring problems by going longer on header pipes)