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Author Topic:   Outerwears/Prefilters restrictive?
Dirt Freak

Total posts: 279
posted February 24, 2003 11:24 AM  
I Hate what a few nights of dirt racing does to a good K+N air cleaner and I don't really want to replace a new paper filter every show. Do you guys know if there is an appreciable power loss or air restriction using an Outerwear screen over a 4" element with the filter top?

Dirt Roller

Total posts: 23
posted February 24, 2003 11:32 AM  
I don't think that they are that resrtictive, but if you have a filter top and a 4in. filter then it don't really matter, there is no way that your carb flows as much air as is being let thru your breather now. What I'm trying to say is you should still get pleny of air even if it was somewhat restrictive. Plus a dirty k&n is going to restrict also and the pre filter is easier to clean.

2002 H.O.T. Street Stock Champion
M&R Racing

Dirt Roller

Total posts: 21
posted February 24, 2003 11:52 AM  
I have switched to the K&N foam pre filter. I tried the outer wears and they seemed to pack with dust. The foam style seemed to keep the air cleaner alot cleaner too. Just have to wash the pre cleaner out everynight.

Dirt Forum Champ
Total posts: 5390
posted February 24, 2003 02:57 PM  
I used to have to clean the clay out of my k+n every other week but now I can go a lot longer. If you don't have any leaks your outerwears shouldn't need cleaned that often. I figure I would rather have a little bit of restriction w/outerwears than a bunch more when it gets covered up with clayduring the race.

Dirt Forum Champ
Total posts: 968
posted February 24, 2003 06:50 PM  
I saw an ad for Amsoil filters.they say they're lots better than K&N Any of you tried them?

Dirt Full Roller

Total posts: 68
posted February 24, 2003 11:12 PM  
I used to run an outerwears on my truck all the time, but it wouldn't pass smog at idle (to rich) until I took it off, so i think it blocks enough air that I wouldn't use one on my race car. I still use it on the truck when I go ripping up the fire roads in the desert though, it keeps the air cleaner, uh, well,......cleaner. I run a stock class so all the power advantage i can get helps me, but maybe you guys in the faster classes don't care so much about 25 or so cfm? just my .02

Dirt Freak

Total posts: 337
posted February 25, 2003 08:44 AM  
I used to run a k&n but after reading on the net and talking to others I changed to amsoil 2 stage foam filter.K&n flows a little more air but also lets dirt get by.I didn't see any signs of dirt damage internally when I tore it down.Have seen others take there k&n filters off and have some dirt and oil mixed laying on the carb, this is not good.Foam filters of the past where marginal but now they are alot better .Take a look at dirt bikes they use to use foam filters.Alot of people at my local track use paper and change it every race.Amsoil filters in independent studies are supposed to flow more air than paper and filter dirt out at about the same percent .The amsoil filter is supposed to last longer than paper before it gets restricted enough to be a problem.I will use the amsoil filter again this year.clean it after evry race and be amazed at all the dirt in the bucket afterwards, use there oil to put back on it which is a little more tacky than k&n oil.this is an area that needs to be right dirt in the motor = dead motor

[This message has been edited by dirtracer7 (edited February 25, 2003).]
Dirt Newbie

Total posts: 2
posted October 06, 2004 03:21 PM  
AMSOIL 2 Stage is the way to go. Check out this article


Dirt Freak

Total posts: 370
posted October 06, 2004 03:50 PM  
Ive been told by my engine builder that he talked to a representative? or someone and they said yes they were. He cleans the one on the mod every week. Washes it and oils it and all that. He also has a spare just incase it gets really dirty in hot laps or heat races.

Dirt Full Roller

Total posts: 33
posted October 09, 2004 01:24 AM  
you guys might find this informative:
It's tests of various air filters including OEM paper for a Duramax. IT deals with exactly this kind of thing- trapping particulate dirt etc.

Outerwears seem to plug up as well with fine dust from what I've seen. I started to use a K&N foam prefilter unoiled over top of a stock paper filter to keep it from damage, seems okay so far.

If you think a K&N lets in no dirt particles, try one on a turbo diesel and inspect the turbo blades for erosion a year later.

Here's the link:

Dirt Freak

Total posts: 226
posted October 09, 2004 05:40 AM  
so what is better K&N or Amsoil??


Dirt Freak

Total posts: 372
posted October 09, 2004 06:31 AM  
i use a k@n and clean i after every race, i ran all last saeson and this season on the same motor, over 40 races combined including a 100 lapper last year and another one next week and the in side of my carb and air cleaner housing still looks like new, i remeber my dads toyota mini having a film of dirt on the carb every night using just a paper filter.jmo

Dirt Forum Champ
Total posts: 968
posted October 09, 2004 06:38 AM  
Great article Mechanist! I've been using the Amsoil for a couple seasons now and enjoy the ease of cleaning and oiling over the gauze K5N. Now I am wondering whether I am going to check out an AC Delco paper...


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