Aftermarket Air Intakes/Filters - Do They Work? - Diesel Place : Chevrolet and GMC Diesel Truck Forums
Home Forum Market Place Garage Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > Power, Performance & Tuning > Fuel System, Air, Exhaust, & Emissions Upgrades
Register FAQ Forum Rules My Replies My Threads Mark Forums Read Advertise

Fuel System, Air, Exhaust, & Emissions Upgrades Discuss upgrades to the Duramax fuel system and air system. Bigger turbochargers, more turbo chargers, air boxes, exhaust systems, emissions systems, and fuel pumps all go here. is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Closed Thread
LinkBack Thread Tools
Old 11-21-2006, 05:56 PM   #1 (permalink)
Diesel Master
INTJ's Avatar
Join Date: Jan 2004
Location: Roseburg, OR
Posts: 1,858
iTrader Score: 0 reviews

Armed Forces Club Member

Aftermarket Air Intakes/Filters - Do They Work?

My goal here is to make sure guys know what they are getting into when they consider changing the intake of their DMax. At the bottom of this post I have include the only independent, scientific, extensive test of DMax air filters that I know of.

I want to emphasize that there has been a lot of dyno testing over the last few years to see if there are any HP gains with an intake for the DMax. The tests repeatedly show no significant—if any at all—increase in HP regardless of the intake system or filter used. Perhaps at power levels in excess of 500 RWHP—and most likely running a bigger turbo–there would be an HP increase.

What is controversial is whether or not turbo spool up time is improved with an aftermarket intake. The problem is there is no real way to test for that and seat-of-the-pants is not a reliable indicator. The aftermarket intakes do increase turbo noise, and some take that to be an increase in responsiveness. However we don’t know for sure. Also, if someone does the exhaust and intake at the same time, then there is no way to know which caused what “feels” to be an improvement.

Another controversial area is the claimed increase in fuel mileage an aftermarket intake supposedly provides. It is very hard to verify small improvements in mpg, especially over a couple tanks of fuel. Again, if someone does the exhaust and intake at the same time, then there is no way to know which caused the improvement.

I installed a K&N Aircharger (the 2002 version of the FIPK) on my 2002 the day after I got it. My mileage constantly improved with the truck for around 18,000 miles. Somewhere around that time I learned of the massive amount of dirt the K&N can let into a DMax so I went to an Amsoil air filter in a swiss-cheesed airbox. My mileage did not change, though the turbo was quieter. When I saw the results of Spicer’s test I changed back to a stock Delco paper air filter. My mileage did not change then either. This has been verified over many tanks of fuel calculated by hand.

Most aftermarket intakes do seal off under hood air. For a couple months I monitored my intake air temps and I found a direct correlation between EGT and outside air temps (OAT). The hotter the OAT the higher the EGT. I installed a TX Christopher Cold Air Intake kit, which is a rubber gasket that seals off the stock airbox, and it did keep the intake air cooler. So I think we can say an aftermarket intake will help lower EGTs by sealing off hot, under hood air.

WARNING—OPINION!! Given there is no HP increase and the MPG and turbo response improvements are questionable, I don’t think an aftermarket intake allows any more air into an engine equipped with a stock turbo. If it doesn’t allow any more air into the engine it is worthless.

What we do know—and what the test below shows—is that the aftermarket air filters do pass more dirt than the stock AC Delco filter.

The question you need to ask is: Is it worth risking more dirt into my engine for no HP gain and questionable gains in MPG and turbo response? That is a personal decision. Perhaps you do not drive in dusty conditions and for you ANY air filter would filter adequately. Regardless, don’t be mad when my Delco paper filtered DMax—running it’s “Kennedy Race Tune”—blows by you, your noisy turbo notwithstanding.....

Here is the air filter test Spicer reported on a couple years ago. This is basically a cut and paste of what is posted at:

NOTE: The pretty color graphs didn’t post—I’ll have to work on that later. However, the graphs are available at the link.

The Story behind the test:

First of all, many thanks to Arlen Spicer and Ken at Testand for organizing and facilitating the test. Arlen is a professional Firefighter who also operates a small tree service on the side. The tree service is the reason he owns a diesel truck. This study was the result of nearly a year of work by Arlen to get accurate independent data on air filters for the GM Duramax Diesel. Arlen originally set out to build his own Filter Test Stand so that he could perform accurate, repeatable and independent measurements on the various filters available for the Duramax. Arlen questioned the claims made by aftermarket filter manufacturers that their filters were superior to the conventional OEM style paper filters. After spending many months, hours and a considerable amount of his own money, he learned first hand how difficult it was to perform an accurate air filter test. He found it was difficult to maintain all the necessary controls to insure an accurate measurement. It was at this juncture that Arlen received a call from Ken at Testand offering to perform the ISO 5011 test free of charge. Ken found Arlen’s idea for an independent comparison study very interesting and offered to do the ISO 5011 testing using one of Testand’s industrial Filter Test Machines. Arlen posted the news in an internet forum and immediately the offers by forum members to purchase and send filters for the test started rolling in. Some members purchased and donated filters and others made contributions to cover the expenses and the cost of shipping the filters to Teststand. It was truly a team effort. The end result is the top quality data presented in this report. The following is a quote from a post in the forum.

(Arlen) SPICER wrote,
“Now that I am not doing the tests and my objectivity is not necessary, let me explain my motivation. The reason I started this crusade was that I was seeing people spend a lot of money on aftermarket filters based on the word of a salesperson or based on the misleading, incomplete or outright deceiving information printed on boxes and in sales literature. Gentlemen and Ladies, Marketing and the lure of profit is VERY POWERFUL! It is amazing how many people believe that better airflow = more power! Unless you have modifications out the wazoo, a more porous filter will just dirty your oil! Some will say " I have used aftermarket brand X for XXX # years with no problems. The PROBLEM is you spent a chunk of ching on a product that not only DID NOT increase your horsepower, but also let in a lot of dirt while doing it! Now how much is a lot? ANY MORE THAN NECESSARY is TOO MUCH!

Others are persuaded by the claims of aftermarket manufacturers that their filters filter dirt "better than any other filter on the market." Sounds very enticing. To small timers like you and me, spending $1500 to test a filter sounds like a lot. But if you were a filter manufacturer and you believed your filter could filter dirt better than any other media on the market, wouldn't you want to prove it? Guess what. Test your filter vs. the OE paper. It will cost you $3000 and for that price you will have the data that you can use in your advertisements. Your investment will be returned a thousand fold! EASIER than shooting fish in a barrel! So why don't these manufacturers do this? Hmmm? Probably not because they would feel guilty about taking more market share.

Now I am not saying that ALL aftermarket filters are useless. A paper filter does not do well if directly wetted or muddy. It may collapse. This is why many off-road filters are foam. It is a compromise between filtering efficiency and protection from a collapsed filter. Now how many of our trucks collapse their filters from mud and water? However, if a filter is using "better airflow" as their marketing tool, remember this....Does it flow better? At very high airflow volumes, probably. BUT, Our trucks CAN'T flow that much air unless super-modified, so what is the point? The stock filter will flow MORE THAN ENOUGH AIR to give you ALL THE HORSEPOWER the engine has to give. And this remains true until the filter is dirty enough to trip the air filter life indicator. At that point performance will decline somewhat. Replace the filter and get on with it.

Hopefully the results of this test will do 2 things. Shed some light on the misleading marketing claims of some aftermarket manufacturers and/or give us new insight on products already on the market that are superior to our OE filter. I stand for truth and will eat my words publicly if my statements prove wrong. I appreciate all of the help and support that you members have offered in this project. It would simply be impossible without your help. A huge thanks to Ken at Testand for his willingness to take on this project. I would be spinning my wheels from here to eternity without his help… SPICER”

Our thanks to Arlen and Ken for making the test happen and providing the valuable test results for the benefit of all.

Sept 2004

This report presents the results of an ISO 5011 test of several air filters designed for the GM Duramax Diesel. The test was independently performed under controlled conditions using a $285,000 machine at Testand Corp of Rhode Island (manufacturer of the machine). Arlen Spicer, a GM Duramax Diesel owner/enthusiast organized the test. Ken an employee of Testand offered to perform the tests at no charge. (These tests typically cost approx $1700.00 per filter). Ken, also a Diesel enthusiast and owner of a Ford Power Stroke Diesel, shared Arlen’s interest in performing an accurate unbiased test of different types and brands of diesel engine air filters. The filters used in the test were purchased retail and donated by Arlen and other individual Duramax Diesel owners. The detailed reports from the test have been compiled and are presented in the following pages. The final pages of this report present the interesting story how and why Arlen organized the test.

ISO 5011 Test:
The ISO 5011 Standard (formerly SAE J726) defines a precise filter test using precision measurements under controlled conditions. Temperature & humidity of the test dust and air used in the test are strictly monitored and controlled. As Arlen learned in attempting his own tests, there are many variables that can adversely affect filter test results. A small temperature change or a small change in humidity can cause the mass of a paper filter to change by several grams. To obtain an accurate measure of filter efficiency, it’s critical to know the EXACT amount of test dust being fed into the filter during the test. By following the ISO 5011 standard, a filter tested in Germany can be compared directly compared to another filter tested 5 years later in Rhode Island. The ISO 5011 filter test data for each filter is contained in two test reports; Capacity-Efficiency and Flow Restriction.

Capacity and Efficiency:
The Capacity and Efficiency test report presents the test results of feeding an initially clean filter with PTI Course Test Dust (dirt) at a constant rate and airflow. The course test dust has a specific distribution of particle sizes ranging from less than 2.5 microns to greater than 80 microns (see table below). Every filter is initially tested at 350 CFM and the Initial Restriction or differential pressure across the filter is recorded in IN-H20 (Inches of Water). The filter is then tested by feeding test dust at a nominal rate of 9.8 grams per minute with a constant airflow of 350 CFM. The test is continued until the flow restriction exceeds the Initial Restriction + 10 IN-H20. At this point the test is terminated and the amount dust passed through the filter - Accumulative Gain - is measured. Dirt passing through the filter is captured in the Test Station’s Post Filter. The exact amount of dirt passed is determined by measuring the before and after weight of the Post Filter. Similarly, the amount of dirt retained by the Filter under test - Accumulative Capacity – is measured by taking the difference between the before and after weights of the Filter. From these results the overall % Efficiency of the filter is calculated. This test also indicates how long a Filter will last before replacement is required (or cleaning for reusable filters).

Flow Restriction:
This report presents flow restriction of a clean filter resulting from an increasing airflow. The differential pressure restriction across the filter is reported in inches of water (IN H2O) versus Air Flow in cubic feet per minute CFM.

Data from these reports has been compiled and presented in the following bar graphs, Plots and data tables.

Filter Efficiency:
Filter efficiency is a measure of the filters overall ability to capture dirt.

Accumulative Capacity:
“Accumulative Capacity” is a measure of dirt holding/loading capacity before reaching the maximum restriction limit - Initial Restriction + 10 IN-H20.

Accumulative Gain:
"Accumulative Gain" is the total amount of dirt that passed through the filter during the test.

(Note: The Purolator was reported to have a seal malfunction during the test and passed more dirt than it would have with a good seal.)

Initial Restriction:
Initial Restriction is the Filter under test’s resistance to flow at 350 CFM.

Dirt Passed Versus Total Test Time

This graph shows each the duration of each filter’s test versus dirt passed (Accumulative Gain).
(Note: The Purolator was reported to have a seal malfunction during the test and passed more dirt than it would have with a good seal.)

In the chart above it’s important to note the different test durations for each filter. The AC Delco filter test ran for 60 minutes before exceeding the restriction limit while the AMSOIL and K&N tests each ran for 20 and 24 minutes respectively before reaching max restriction. In 60 minutes the AC Filter accumulated 574gms of dirt and passed only 0.4gms. After only 24 minutes the K&N had accumulated 221gms of dirt but passed 7.0gms. Compared to the AC, the K&N “plugged up” nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt. See the data tables for a complete summary of these comparisons.

Dust Loading:
The dust loading curves show graphically how each filter responded to a constant 9.8 gms/min dust flow before reaching the maximum restriction limit.

It’s interesting to note the shape of these Dust Loading Curves. The AC and Baldwin filters each had near linear responses until reaching maximum restriction. Restriction for these filters increased at a constant rate versus the 9.8 gms/min dust feed rate. The other filters, most notably the oiled reusable types, had an exponential loading response before reaching maximum restriction. These filters had a lower initial restriction, but they became exponentially more restrictive under a constant flow of dirt. Also notice the length of the curves as it shows the relative test time for each filter (time to max restriction).

Restriction to Flow:
The Restriction to Flow curves graphically show how each “clean” filter responded to a steadily increasing flow of air up to 350 CFM.

The Flow Restriction response curves for each filter have the same basic shape. However, note how the AC Filter, which passed the smallest amount of dirt and had the highest dirt capacity and efficiency, also had the highest relative restriction to flow. The less efficient filters correspondingly had less restriction to flow. This illustrates the apparent trade-offs between optimizing a filter for dirt capturing ability and maximum airflow.

Test Data Tables:

Test Data Tables:

Test Data Tables:

Test Data Tables:

Test Data Tables:

Test Data Tables:

To be consistent with common industry practice all filters were tested using PTI Course Test Dust. Course dust is more commonly used since it will produce higher % efficiency numbers.

Attached Images
File Type: jpg accumulativecapacity.jpg (35.4 KB, 32842 views)
File Type: jpg accumulativegain.jpg (33.6 KB, 32930 views)
File Type: jpg datatable1.jpg (79.0 KB, 32558 views)
File Type: jpg datatable2.jpg (69.0 KB, 32396 views)
File Type: jpg datatable3.jpg (94.3 KB, 32392 views)
File Type: jpg datatable4.jpg (76.7 KB, 32176 views)
File Type: jpg datatable5.jpg (75.7 KB, 32082 views)
File Type: jpg datatable6.jpg (59.1 KB, 31978 views)
File Type: jpg dirtpassed.jpg (41.1 KB, 32723 views)
File Type: jpg dustloading.jpg (38.5 KB, 32621 views)
File Type: jpg dustspecs.jpg (13.2 KB, 31819 views)
File Type: jpg filterefficiency.jpg (36.3 KB, 34534 views)
File Type: jpg initialrestriction.jpg (35.4 KB, 32606 views)
File Type: jpg restrictiontoflow.jpg (36.4 KB, 32653 views)
2011 CCSB Z71. Duramax Tuner, FASS, Banks Intake, Edge Insight CTS.

Previous Trucks:
- 2002 CCSB 4x4 w/Sun Coast Stage IV, Kennedy Race Tune, Tuff Country Lift, Kennedy Lift Pump, Nicktane, 4.1 Gears
- 2009 XCLB Z71, Banks Six Gun
Quick reply to this message
Sponsored Links
Old 11-27-2006, 03:46 PM   #2 (permalink)
RickDLance's Avatar
Join Date: May 2004
Location: Holden, MO
Posts: 10,624
iTrader Score: 1 reviews

General discussion concerning this can be found here;

Please feel free to voice your opinion. Thanks!


27 Duramax's so far!!

We also handle S & B filters, Air Dog lift pumps, and Kraftwerks Superchargers.

Special Thanks to my Sponsors!!
Danville Performance, SoCal Diesel, Vibrant Performance, & ProFab Performance!!
Offline   Quick reply to this message
Sponsored Links
Closed Thread

Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Aftermarket Air intakes? Who's runnin one? Freestylest22 Fuel System, Air, Exhaust, & Emissions Upgrades 18 03-25-2011 08:13 PM
True Flow intakes and filters---good or bad??? wveric Fuel System, Air, Exhaust, & Emissions Upgrades 3 07-18-2007 04:32 PM
New AFE Pro Dry S Filters & Intakes gautoparts Fuel System, Air, Exhaust, & Emissions Upgrades 0 02-09-2007 10:03 PM
Air Filters and Intakes effect on EGT? Highmark Fuel System, Air, Exhaust, & Emissions Upgrades 6 03-06-2005 02:02 AM

All times are GMT -4. The time now is 12:27 AM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide