Air Filter observation

Dec 21, 2009
I just hit 10k miles on these Wix 49362 filters. In my G37 (VQ37VHR) and went to see how dirty they were and hit them with my Wetvac while I was vacuuming the inside of my car.

I noticed both filters show pleats looking like the below which to me looks like this filter is being too restrictive?

I have a monometer and I'm itching to install some barbs on the OEM intake boxes.


Engine flows ~225 CFM per filter(bank of 3cyl) at 7500 RPM, filters are 6.7 x 7.2" from the spec sheet but the dirty area is quiet a bit smaller.
I'd assume the OP is referencing the pleat spacing, but I wouldn't agree it was restrictive.

The pleats did not start out like that :D Only way for them to be moved apart like that is if there is "enough" Dp across the filter causing the pleats to separate. I have not seen a used air filter do this on other cars though, it again is just an observation. Sounds like I will be installing a monometer and getting some data on this used wix and new filters I have on the way.
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Good eye. I wonder how it compares to another brand filter after those miles. Obviously a new filter is going to flow better (well, most of the time).
Sounds like I will be installing a monometer and getting some data on this used wix and new filters I have on the way.
Only way to know ... but you'd have to do it on a new filter and watch it along the way. I highly doubt the pleat spacing is causing any noticeable increase in delta-p across the whole filter.
Got some Data :)

Used Filter : Wix 49362 (60 Pleats/Orange Gasket)- 9505 Miles and 381 days in service.
New Filter: Mahle LX3070 (60 Pleats/Black Gasket)
Data Recorded using EcuTek, HT-1890 Monometer, and a video camera.

70F Exterior Temps and 75F IATs

Test Procedure: Place car in 2nd Gear, Set cruise control at ~30mph. Then hold the cruise control +speed until Redline (7500 RPM). This takes about 20 seconds.


Test Procedure: While in 2nd gear coasting from redline, Go WOT at 6k RPM, record peak pressure delta.

Used Filter: -5.46 inchH20
New Filter -2.205 InchH20
59.6% Reduction in Pressure Drop with new Filter.

Filter Overlay Shots: Note WIX Has a smaller filter area due to gasket thickness/molding process.


IMG_20221025_0005-10.pngIMG_20221025_0006-10.png PXL_20221025_2216504422.jpg


test setup.jpg
I love it! No more guesses, real data! Good work! I've always beleived that a new filter would be less restrictive, makes sense, less dirt. But that's assuming that the filter (old vs new) are the same quality, same air flow. The new one you tested is much better, obviously. It would be interesting to see that now you have a base number to work from, how the new one changes as it loads up with some dirt.. I bet you'll keep us updated.
I applaud you for your efforts. But without any efficiency numbers it’s kinda mute. A screen door will flow more air than an air filter. More flow better or cleaner air better ? Biggest difference at redline. Unless racing you and your motor would never know the difference putting around at 2k rpm.
As the filter media loads up with use of course the pressure differential across the filter will increase with time. Every filter will show this behavior as it is used.

You state "Only way for them to be moved apart like that is if there is "enough" Dp across the filter causing the pleats to separate.". I disagree. That media is essentially paper. Perhaps paper with some synthetic components, but none the less mostly (or completely) paper.

That paper is subject to wild swings in temperature and humidity as you drive through rain, snow, fog, the heat of summer, etc. You take a piece of paper and leave it outside (but protected from rain) for a year and see if it remains nice and flat. Spoiler alert ... it won't. And what that filter will see as you drive around for 10k-20k miles is far worse (what with the heat of your engine bay and all).

Just as a point of reference, the filter in my Honda push mower shows a similar warping/bunching of the pleats over the course of a year and there is almost no pressure across it.

BTW, your worst case 1.4 inH20 is about 0.05 PSI. And that's at an engine rpm that you probably aren't going to be spending a lot of time at.

So the real question is, are your worst case pressure differential numbers excessively high? And the answer is, unless you are tracking the vehicle almost certainly not.
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