A hypothetical question re: air / fuel mix

[mrflibbles]

Ive been thinking lately (all hypothetical):

Say for eg you took the air filter out of your car. Assuming the air was completely clean (so no nasty particles to worry about) this would result in more air in the engine, hence a greater air : fuel ratio in the cylinders, ergo the engine would run lean. Am I right thus far?

So.

These 'performance air filters' alledgedly provide an easy path for air into the engine. Hence, more air in cyls etc etc. Result - lean running - poor performance.

So, when using these aftermarket filters, why dont you have to get yur mixture adjusted?

[mrflibbles]

twin40s said:

Depends on your engine. If you have carbs then the amount of fuel drawn into the cylinde is proportional to the speed of the air flowing through the carb (well approximately) more air means faster flow, means more fuel. If you have injection theres a thing called a lambda sensor which detects if if the mixture is correct, if its not the ECU will correct the fueling to suit Simplified description but near enough In both cases this only works if the change from standardf isnt too big

So does the ECU learn instantaly? presumably making changes every second, or does it 'take averages' over a few hours / whatever?