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Discussion Starter · #1 ·
Ok...In gas engines....K&N Air Filters are supposed to be the BOMB. But what about in a diesel engine....I hear NOTHING about air filters. Are they worth replacing? And is K&N good?
 

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stay away from K&N filters for the diesels they let to much dirt past them in to the turbo housing..
 

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Yes, stay away from the k&n....in most cases you do not "need" to replace the air filter, people just do. I bought an AFE intake with their proguard 7 filter because I thought it would give me some gain...really the only thing I gained was more turbo noise, which is nice. I still run my stock intake when I drive a lot of dirt roads since you can't beat the stock filter on keeping dirt out of the engine.
 

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I just want to say THANX to you guys....this forum and all your posts help me out ALOT. I was going to buy one yesterday...and thought I better ask the pros first. I'm glad I didn't. THANX
 

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Their cold air intakes are a little different....I know they used to throw MAF sensor codes. Try holding the filter up to the sun or a light and see how many pinholes you see light through. The K&N filter flows better, but lets more dirt in initially. Why do you think they tell you they filter better the dirtier they get? Go to Yahoo or google and do a search on "Spicer filter study." You will be surprised at what you find out.
 

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I put a Fram Pro Guard filter in mine over 4000 miles ago and it barely looks dirty. I also did the Kennedy airbox upgrade the other day with some screening around it to keep the bugs out. Seems like letting more of that air in now has changed my shifting points on the tranny. Guess I will go to the stealership and see if the can upgrade the computer and for how much?
 

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with a stock duramax and stock turbo you don't need a CAI but if you want to make a small improvement you can do a drop in filter from AFE,S&B,Amsoil and there a few others that build them..
 

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Out of curiosity, did you do the same test with a CAI? I don't think it would make much of a difference sitting at a light with either intake unless you had a functional ram air hood.
 

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i have never seen a diference in performance with or with out a CAI untill i did a turbo upgrade on my 05 LLY i noticed it sucked really hard so i did a S&B CAI and it ran better..now i don't know about the aftermarket CAI verse stock CAI temps..this info is just from my experience..
 

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Out of curiosity, did you do the same test with a CAI? I don't think it would make much of a difference sitting at a light with either intake unless you had a functional ram air hood.
I did. i would see 190 at lights, stock. After the CAI that I use was installed, it never gets above 130. It still rises, but not near the kind of peaks I was seeing.

It turns out, this IAT rise is so important, it even makes a difference on how much fan you get. I don't have a scientific result to show you, but my fan time running in town is much less than before the intake.

Think about it also. That 200 degree airbox air gets even hotter in the turbo and heats the CAC more. The CAC sheds this heat, past the radiator to the fan clutch, and then the fan comes on.

That stock box is a menace, but probably not so much so in alaska. :)

I did tow in 100 degree weather. And from stop light to stoplight, the IAT heated up to 260 degrees. When I tried to pull away from that light, it just hickuped. It was so slow to accelerate, till I got to 40 mph or so, i thought it was going to just quit. Thats when I got the intake, and that hasn't happened since.
 

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AFE all the way!

K&N in the duramax can get sucked in and lets in dirt
 
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