This question about filter quality ignores one of the main causes of particulate matter entering an engine, IMO. By focusing on the filter itself, you are ignoring organic and mechanical failures, to focus solely on the performance of the filter media. This is similar to comparing a Mustang GT and WRX Sti based on paper track numbers in a magazine, and then going to race and finding out a light mist is on the track. Your careful hp/tq/lb calculations just went out the window, and now the AWD of the WRX STi is going to stop a mudhole in that RWD Mustang GT.
Similarly, when focusing on the filter media, you are ignoring the manner in which it is to be used. Most factory induction systems feature an "airbox" and the filter is sandwiched between a lower (dirty) half, and the upper (clean) half. It is secured with several spring-type clamps, typically. The tension on the filter gasket is both imprecise, and minimal. Vibration of the airbox, flex, low tension, varying vacuum, can all then play a role in particulate matter bypassing the media all togather. A chain is only as strong as its weakest link. In comparison, many aftermarket systems feature a much more secure method of attachment, involving T-bolt clamps on every juncture. Note the one below, which I just installed on my turbo CX5:
Also, I took some photos of the inside of the intake tube leading to the turbo, as well as the "clean" side of the filter housing box. The dust on my road is indeed white. The filter is OEM, and has been changed at least once, maybe twice, at regular interval over 35.5K miles I have put on the vehicle. I have done this myself, each time, verifying correct placement of the filter and closure of the clamps, which indeed were properly secured at all times I have inspected them, including this removal. Based on the distribution of the contaminant within the "clean" side of the intake box, one can see and deduce how this contamination got there...it wasn't via passing through the excellent filter media. In each of these photos, I have wiped an area to show surface distribution of contaminate via contrast.
In this way, I feel that it is very deceptive and overlooking the "system as a whole" to fixate upon filter media exclusively, as I am willing to bet that my "99.4% cumulative efficiency down to 1 micron" AEM filter and intake assy. is likely to vastly out-perform my OEM filter and intake assy, even presuming the OEM filter is slightly more "filtery", due to the integrity compromises made in the OEM filter assembly housing.
Also, based on the advertisement from CS's dyno chart, I gained 8-12whp. I independently verified this myself, and have concluded that yes, this is likely accurate, based on acceleration times 20-80mph. Yes, the BOV and turbo are actually quite noticeable with the radio off, as 17psi is 17psi. I am very impressed with the noise cancellation the OEM managed! As far as the filter location being "hot", after driving for an hour, I parked in my garage, popped the hood, and felt the bolts on the clamp near the filter. It felt cool to the touch, as did the rest of the assembly. Ambient was around 60*F, and it felt 60-80*F to my touch. Further, the front mount intercooler post-turbo kindof negates a CAI purpose anyways, even if it did pick up cooler air, which it doesn't seem likely given my observations and track and dyno testing done by CS and their tuner and others, 3rd party.
Originally Posted by OVERKILL
Originally Posted by wemay
While on throttle, every vehicle can take in more air than a typical filter will flow. The less restrictive a filter, the more air that's sucked in.
Nope, that's backwards. Most filter's CFM rating is significantly higher than the flow rate for the TB. For example, I had a 75mm throttle body on my 302, which was mounted to a TFS-R, feeding a set of very heavily massaged GT40's. It was connected through the factory intake plumbing, which was ~90mm in diameter, to the stock Fox panel filter, which was about 12" long by 9" wide (going by memory). IIRC, the flow rating for that panel filter was ~1,250CFM. The maximum that TB would flow was ~920CFM without forced induction (N/A application) and at ~325HP (flywheel) I was consuming nowhere near that.
As I said earlier, you can easily verify if the filter is a problem using a vacuum gauge plumbed into the box or plumbing on the clean side of the filter. The K&N filter restriction gauge is probably an ideal fit, as it is both very sensitive (much more so than the typical diesel ones) and locks in place at the restriction level, so you can go out, do a WOT run and see if it showed any restriction.
Here's a CFM calc:
https://racingcalcs.com/cfm-cubic-feet-per-minute-calculator/
If I plug in my 392, and get ridiculously generous with the VE, putting it at 90%, at 6,500RPM, my air requirements are only 663CFM. The factory filter flows 1,080CFM.
EDIT: Actually, we can get much more accurate here, as they have a displacement + VE to HP calculator too, which also gives CFM requirements:
https://racingcalcs.com/engine-horsepower-calculator/
So, my 392 makes 475HP, so VE is 88%, which pegs my CFM requirements right around 650, meaning the factory filter is VERY generously sized.
Spreadsheet analysis < Results. Better intake setups do make power, and do typically put down 1-3mph trap speeds, depending on the vehicle. It's just how it is.