How often do you change the air filter?

[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.

[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.

[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]

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.

[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.

[TorqueEffect]

After watching that mightycar mods video on the air filters, and pod filters, I pretty much decided it isn't worth it.

https://www.youtube.com/watch?v=PAIxeQUSg-Q

[rmoltis]

So I had a stock box I had modded with a wider opening before with this k&n filter
And because of the reduced velocity of the incoming air charge due to more opening it actually lowered my volumetric efficiency.
I ended up buying a new stock intake box to recover my low end lost.
And not to mention even with a header and the stock box with k&n filter it will flow as good or close to a replacement cone filter.

[TominMO]

That could be. I did install the Aspire intake tube, which is larger in diameter that the flattened Festy one. The main advantage to the K&N; besides increased flow; is that you only have to buy one,ever.

Agreed.

[navdoc101]

That could be. I did install the Aspire intake tube, which is larger in diameter that the flattened Festy one. The main advantage to the K&N; besides increased flow; is that you only have to buy one,ever.

[TominMO]

I modded the stock air box, drilled the bottom full of holes & removed the little snorkle on the fended side. & I have the K&N. Must flow better than the stock filter & moded box!

True--but, the question at this point is how much air can get into that small plastic tube going to the throttle body? I think the stock filter with a modded airbox will do as well as the K&N. This is what should be studied.

[navdoc101]

I modded the stock air box, drilled the bottom full of holes & removed the little snorkle on the fended side. & I have the K&N. Must flow better than the stock filter & moded box!

[TominMO]

Just toss the lower airbox, or drill it full of holes. I would guess that would yield you a greater flow than using the K&N with a stock, unmodified, restrictive airbox. At that point some other part of the intake is the restrictor, not the airbox/filter.

If anyone has any valid research on this, it would be interesting for you to chime in here.

[JMSA540]

sorry to bring up a dead thread, but I found this thread to be very informative.. also cool how it flows 10% over stock.. good read.

[rmoltis]

I was gonna say that was the filter I have as well. I always look up the Mazda demio for referance because they are the same filter as well. So festiva 1st gen, second gen, and third gen all have the same filter.

I compared a brand new stock filter to this one after it had just been cleaned the night before and the stock filter got me %75 volumetric efficiency. Whereas with the k&n I get an %85 volumetric efficiency. This was all based off of my scanguage II feeding me data from the ecu. So I noticed a %10 power gain. It didn't seem like much with the stock exhaust when I had it but it gave me torque at low end. Then when I got my header and exhaust the power band shifted and the midrange fattenned up quite a bit. The peak torque point being now at 4300rpms. That's when I realised the stock airbox flows more than even neccassary. Would reccommend the washable k&n to anyone who still uses the stock box.

For $40 its the best bang for buck for a gain in up to %10 power without sacrificing low end for a pod filter.
Well worth the money in my opinion. Don't ever buy a paper filter again.

[navdoc101]

K&N drop in filter that fits the Festiva air box is part # 33-2222. Same as '93 KIA Pride.