RNSAK

So i went a little far down the rabbit hole researching air filters for my truck, found some interesting info. Long story short it appears most Silverados, Tahoes, escalades bla bla 4.8/5.3/6.0/6.2 2000-2018 use WIX 42488, that means the factory filter my truck came with is at the very least good enough to support 420hp/460ftlbs (output of new 6.2). But I also discovered the 01 to 05 duramax's used WIX 46678 which is basically the exact same dimensions as 42488. I contacted wix to find out the differences between the two, without much help but I did find out how they calculate the CFM of their filters, and it would appear according to their calculation the 42488 filter will flow substantially more CFM than the 46678. Which seems counter intuitive considering it's on a turbo charged diesel with much higher power output than the gas motors. The 46678 has 41 pleats, the 42488 has 77, but all the CFM calculations I come up with for 42488 are nowhere near the 320CFM the rockauto page lists?? I realize most of this is fairly redundant but I thought id share none the less.





WIX CFM CALCULATION (42488 pleats 77, Length 12.2, Depth 2.4) LD
(46678 pleats 41, Length 12.25, Depth 2.375) HD


PLEATS X 2 X Length X Depth


Divide by 144


Multiply by 7 for HD filters
Multiply by 30 for LD filters

RNSAK

R U Jimmy Ray

So, do more pleats ADD CFM (more surface area), or do the restrict the airflow (packed in there too tight)? I'm interested....

RNSAK

generally speaking yes I believe so, more pleats means more filter media surface area/more CFM and according to WIX's formula as well. I compared the two filters side by side and other than the pleat count the only other difference I saw was the filter media on the 6678 appeared to be slightly more course..........however the 6678 is listed as having a 99.7% efficiency rating while the 2488 is right at 99%

RNSAK

ISO 5011 Duramax Air Filter Test Report


heres a great write up on air filter performance using the 46678 against K&N, AFE and many others.


Also heres some fun math, assuming a 6.0 is about 85% volumetric efficient which is generous, that means it will displace 5.1L per combustion cycle, which is two crankshaft revolutions.


5.1L is .18 cubic feet, .18 X 1800 (3600RPM)= 324 cubic feet a minute (CFM)


with a max of 495 CFM at 5500 RPM, so even at red line the factory air filter rated at 320CFM should be plenty sufficient for any HP needs, at the worst its pulling a very slight vacuum.

05GMC4.8

Pretty cool info

RNSAK

So I finally heard back from WIX regarding the inconsistencies in their CFM calculation they cited. Thats just a rough calculation, their actual listed CFM rating is done through various dirt loading tests to give real world CFM ratings. Also regarding filter 46678 according to WIX they rate it at 500 CFM, so anyone looking for a high flow drop in replacement filter, the 46678 should be a good replacement for the factory 42488 which is rated at 320 CFM by WIX. Now would that net any real power gains in a lightly modified truck? No probably not, but IMO its a far superior alternative to any aftermarket cotton gauze oiled/unoiled filters available. I hope to be doing before and after dyno runs in the next month or so after a cam and intake swap and I will be testing the two filters just to see if any difference is seen.

akcooper9

Have you tried the 46678 filter?

RNSAK

No I haven't yet, between work and family life I haven't had any time to play, hopefully this next time I'm home for R&R I can get into it..........at the very least I can monitor g/s through the MAF with my trinity to see if there's any difference. Like I said before I don't feel like it will as the air flow demand of a mostly stock LQ4 is no where near the limits of the factory 42488. But all the same ill probably start running the 46678 to eliminate the possibility not to mention its air flow/dirt loading performance curve is superior to any aftermarket drop in IMO.

R U Jimmy Ray

I just purchased an AC Delco A1618C for my SSS.