Not really. The test I've read was comparing various popular filters. They compared K&N washable, APEXi dry cloth, HKS foam, Blitz metal, and an original paper filter. The result was the APEXi provided the best filtering AND surprisingly also matching the rest in terms of power gains over the original filter! K&N came 2nd providing about the same power gain but just slightly more dirt and oil penetration. HKS next with pretty dirty result, then the Blitz was like very dirty and both these filters also surprisingly did not provide additional power over the APEXi or K&N! So in summary using the metal and foam filter is not recommended coz nothing special in terms of power gain yet the filtration were bad.
I saw that test. But the test bed was dated. These days cars have MAF/MAP and adjust based on the amount of O2 and airflow, etc. I've personally tried a few filters and methods :
1. Drop in K&N : normal filter, serviceable but the oiling was tricky. Too much and it'll clog the sensors with oil. Kena a few times before. Performance was better than stock paper but not much. Could just feel less restriction when revving low to mid-high.
2. Drop in metal mesh : mid to high worked better compared to stock paper filter. Free-er to rev in that range and more responsive. But it only filtered out reasonably large stones and leaves. Small dust particles and mud still went through. EO got dirty real fast and kept constantly needing to clean dust from the TB.
3. Apexi Open pod with insulated air ram and CAI hose directing from the front bumper (no heat shield) : This was pretty interesting, lots of revs but no power gain at all. Very loud noises and the high rev range was very responsive but heavy loss of low end torque.
4. Apexi open pod inside stock airbox and stock everything. Original U-snorkel removed so air in bumper was going upwards directly into the airbox. : Loud noises, mid to high rev range was good but still some loss in low end torque.
5. Stock everything except original drop in filter was cut away leaving only the frame and the Apexi open pod was connected to the end of the U-snorkel in the bumper : This setup worked great. Improvement across the rev range and no loud induction noise. Problem was the pod got dirty verrrrrrrrrry fast. Accessing it was easy for me though.
6. Custom piping from the intake all the way down to the bumper (full straight piping and insulated) connected to the Apexi open pod : This worked even better than stock. The setup was flimsy cuz the piping was only held up by cable ties and the clamp at the manifold. Improvements across the whole rev range.
8. No air filter and direct from CAI into the manifold : This was stupid. Loud and no power gain whatsoever but the revs were so light but didn't translate into any usable power. It would rev to kingdom come without any restrictions though, so that was good for high end revving.
All tested in my wira with front bumper that had a hole with a velocity stack type hole directing directly at the u-snorkel / apexi open pod, similar to M3 design. Hehehe.. yeah right. Anyway, worth noting car was not stock. So for it to adjust to the extra air, it did produce some notable differences.
All these tests proved that there were no improvements in power, just shifting the usable torque / powerband and that the stock setup isn't that bad. Also it helped me figure out that if your car isn't modified for that much air, it won't make much of a difference. So morale of the story is mod your car.
---------- Post added at 08:10 AM ---------- 6 hour anti-bump limit - Previous post was at 08:03 AM ----------
Sh*t... I re-read what I typed and even I'm confused. Hope you guys understood all that crap.