How often do you change the air filter?

[mikeyjd]

From what I've seen of several independent studies done on aftermarket air filters, none of them show anything outside the range of stock for air flow to the engine. If you're looking for more top end power you'd want to do a forced ram air intake and warm air intake.

[TominMO]

From what I've seen of several independent studies done on aftermarket air filters, none of them show anything outside the range of stock for air flow to the engine. If you're looking for more top end power you'd want to do a forced ram air intake and warm air intake.

And intake and cylinder head mods, and improved exhaust. No cheap fixes for real power.

[Bathtub Tom]

From what I've seen of several independent studies done on aftermarket air filters, none of them show anything outside the range of stock for air flow to the engine. If you're looking for more top end power you'd want to do a forced ram air intake and warm air intake.

I always understood that a cold air intake produced a denser charge. Denser charge equals more air. More air equals more oxygen. More oxygen means more fuel can be mixed. More air and fuel means a bigger bang?

[TominMO]

I always understood that a cold air intake produced a denser charge. Denser charge equals more air. More air equals more oxygen. More oxygen means more fuel can be mixed. More air and fuel means a bigger bang?

Yes, but the CAI is just one ingredient in the whole pie. By itself it can do little, because the next limitation is the intake tube between the MAF/VAF and the throttle body. The CAI needs to be partnered with other flow improvements to the intake, combustion chamber, and exhaust. IMO what works just as/almost as well as a CAI is airbox mods, and it's free.

The main reason that modding or removing the lower airbox is an improvement is when the hole for air to come into the airbox is smaller than the hole for it to exit it, into the MAF. I made great improvements in revability, over 4000 RPM, to my old Subaru by drilling about 25 holes in the lower airbox, because the intake hole was about half the size of the hole exiting the airbox! The stock design left it starved for air at higher RPM. Like running while breathing thru a straw.

[mikeyjd]

Yes, but the CAI is just one ingredient in the whole pie. By itself it can do little, because the next limitation is the intake tube between the MAF/VAF and the throttle body. The CAI needs to be partnered with other flow improvements to the intake, combustion chamber, and exhaust. IMO what works just as/almost as well as a CAI is airbox mods, and it's free.

The main reason that modding or removing the lower airbox is an improvement is when the hole for air to come into the airbox is smaller than the hole for it to exit it, into the MAF. I made great improvements in revability, over 4000 RPM, to my old Subaru by drilling about 25 holes in the lower airbox, because the intake hole was about half the size of the hole exiting the airbox! The stock design left it starved for air at higher RPM. Like running while breathing thru a straw.

I don't have knowledge about Subaru's air box's, but isn't a festiva's oval/rectangle intake similar size to a air intake housing that connects to the throttle body? Warm air intake allows for higher temps which lead to more efficient combustion (better fuel economy), so it just depends on what your looking for I guess. I think it's a matter of low end efficiency vs higher end perfomance when deciding between WAI/HA vs CAI.

edit: a-b-a testing on WAI has shown 2-4% increase in fuel economy.