Car air filter/ box question

On my car it only needs to be replaced every 4 years, so maybe it's to increase the service interval? Could also be something to do with higher specific power outputs - years ago 80bhp would have been OK for a 1.8 litre engine, now 125bhp is common. More power out generally means more air in.

Biggles (Remove packaging from my e-mail address to e-mail me.)

generally engines are larger and have higher performance now, therefore they need more air. Also it is generally accepted that cars should be quieter, a larger air box achieves that. Air filters are replaced on a service schedule based on mileage (hence volme of air through them) and/or time basis (number of seasons of rubbish) AFAIK there is no correlation to air box size and FI

Increased volumetric efficiency and service intervals would be the drivers.

VE is increased by the fact that the filter's larger, and there may be some resonant tuning going on in there too. Service intervals are increased by the fact that the filter is larger again.

Thanks - my point was more related to the size and apparent complexity of the plastic box which precedes the filter. (I have a 1.4 Honda Civic but the box is enormous. The filter is not particularly huge.)

Because modern air contains about ten times the CO2 that old fashioned air contained. At least.

I believe noise reduction plays a part. It probably also acts as a buffer to incoming air temperature/humidity changes which allow the emissions control gear to work better.

None of the above. It's to increase the storage capacity, see here -