Magnum Force
Performance Air Intake Systems by AFE
for the Duramax Diesel

By Jim Bigley

Squeezing the last bit of performance out of a turbo diesel involves improving exhaust flow and intake airflow. Performance air intake systems are the best way to help your engine breathe, and AFE produces a line of products to help achieve maximum intake airflow. Documenting performance improvements using a chassis dyno helps answer many questions, and we thought you might be interested to learn what we discovered after installing an AFE Stage II performance air intake system on our 2001 GMC 2500HD equipped with the Duramax/Allison.



Large diameter, powder-coated and mandrel bent steel tubing included in the Stage II kit provides minimal restriction between the air filter element and the turbo inlet flange. It is more important to have a low restriction flow path on the low pressure side of the turbo than on the high pressure side. A large diameter and smooth flowing tube helps achieve maximum airflow.




There are three different versions of the AFE oiled-gauze filter element. There is the standard 4-ply blue media shown on the right in this image, the 7-ply Pro-Guard 7 tan colored media and another 4-ply blue version that has an open end with an inverted cone filter element inside for even more element surface area. The first two have a respective part number of 24-90008 for the 4-ply version with blue colored pleats (the high-flow element), and the 72-9008 for the 7-ply Pro-Guard version. The 7-layer Pro-Guard element is tan in color, and would be better suited to severe dust conditions or for those seeking maximum dirt capturing effectiveness.



You'll need to remove the Mass airflow sensor from the factory air box, and then re-install it in the new AFE inlet tube. GM uses the odd tamper resistant Torx screws to secure the MAF sensor to the air box. Luckily, AFE includes the special Torx bit in the kit.






This is the factory air box mounting bracket. Remove the five bolts, then lift the plate out of the truck.








Apply the larger rubber seal around the top of the AFE air box, and the smaller rubber seal around the inside of the air tube opening. The steel AFE air box will then bolt on using four of the original bolts - using the same bolt pattern.








Insert the rubber isolation mount into the side of the air box, then slide the end of the AFE inlet tube into the opening.







Don't tighten any clamps or hardware till you've successfully attached the opposite end to the turbo inlet using the included rubber adapter and clamps. Once the tube is positioned where you want it, tighten all clamps and the nuts on the rubber isolation mount.

Now, re-install the MAF sensor using the new screws included with the kit, then install the new AFE air filter.






Aside from looking cool, the free-flowing design is evident from this image - maximum airflow through minimal restriction. While not shown in this image, the AFE Stage II kit allows you to retain the factory engine cover.







AFE also produces a Stage I air intake system for those who wish to retain their factory air inlet duct between the air box and the turbo. We used an AFE Stage I system for our current Duramax powered 1989 Chevy Hot-Rod due to a lack of hood clearance for the 4" mandrel bent tubing included with the Stage II kit. Both kits include a steel element housing that seals out hot under-hood air when the hood is closed. Cooler intake air means more power.





We ran our 2001 GMC with stock power and again with a DSG PowerBox on a chassis dyno to compare the Magnum Force AFE Stage II air intake system to a stock air box equipped with a Uni-Foam air filter element. Our dyno tests at stock power showed the AFE kit produced a gain of 7 horsepower. When ran with the DSG Powerbox set to its highest setting, we recorded a gain of 5.2 horsepower above the level produced with the factory air box and a clean Uni-Foam air filter element. The power gain would have been even higher if we had compared the AFE to a factory AC air filter element. The Uni-Foam air filter is a low restriction element, and does a pretty good job, but a 5-7 horsepower gain produced by the AFE Magnum Force kit is only part of the story.


While running this truck on the dyno, shop owner Jeff Davis also reported the AFE intake systems lowered exhaust temperature by 50° F. When combined with a noticeable improvement in turbo response and a bump in power, the AFE air intake system becomes an excellent addition to any turbo diesel performance improvement program.  TDP


Advanced Flow Engineering
Call: 1-909-898-3569 -- Fax: 1-909-489-8705

AFE Retailer:

US Diesel Parts
2400 Palmer - Missoula, Montana 59808
Call: 1-800-823-4444 -- Fax: 1-406-721-5097

DSG Powerbox Retailer:

Diesel Services Group
230-29th Street East
Saskatoon, Saskatchewan Canada S7L-6Y6
Call: 1-800-667-6879 Fax: 1-306-242-5457

Spokane, Washington area chassis dyno:

Davis Diesel
7503 E. Sprague Avenue
Spokane, Washington 99212
Call: 1-509-892-3836

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