Air filters on a dirt track car???

[BLstangin]

What filter do you guys recommend for a dirt track car that gets raced on dry tracked. I had a motor I built fresh this winter and it got 18 nights on it and started using oil when I took it apart I found about .0015 bore wear and the rings had opened up to .100 gap and the tops and bottoms of the rings were shiney.When I inspected the carb I found the inside of the carb throat had actual dirt stuck to it, the guy racing it was using a paper partsmaster air filter from the local race trailer and changing it every couple nights, we have the filter sealed up tight to the lid and base and the base sealed up to the carb, at least as far as I can tell, you can see a clean ring on the filter where it looks like it seats down and a shiney spot on the lid and base all the way around like it's touching everywhere. I'm just wondering if the cheap paper filter is letting all kinds of dirt by? Would a oiled filter such as a k&n be a better solution for a dirt track? My though is the oil catches the really fine stuff, does that make any sense? What does everyone else use on the dirt track?

[englertracing]

Knn is the worst filter for dirt......

[pamotorman]

I used a firewall air cleaner where we picked the air up from inside the car. this was on a late model type car . sealed the air cleaner to the carb and filter to the air cleaner housing with auto body non hardening dum dum

[MadBill]

Knn is the worst filter for dirt......

But K&N was designed for dirt(desert) racing and some feel it is by far the best for both filtration and minimal restriction...

[midnightbluS10]

Huh? I thought everybody knew they were originally made for racing and then street motorcycles. I don't think they ever claimed to be the best, either. Only that they lasted longer and were reusable and were high(not highest) flow. At least in the beginning, IIRC. I could be wrong, though.

[Krooser]

Lots of guys swear by the R2c filters and the Outerwear filter covers.

http://www.outerwearsracing.com

[Momus]

Take your cue from off road racing motorcycles. Without exception they use oiled foam, often multilayer. No one uses paper elements because they leak fine particles. I make my own foam filters from a 16 mm foam supplied by UNI for the purpose. Joining is done with contact adhesive.

[Sodbuster]

I'm no expert by any means, but we won 2 track championships (on dirt) and ran the same engine (383 SBC) for, four seasons using a generic KN type filter with an outerwear. When the engine was freshened each winter there was no abnormal wear. The filter element was cleaned and oiled before each race.

[MadBill]

I've seen a lot of guys running K&Ns dry. It does make a difference!

[pcnsd]

I like pamotorman's solution. It shines a light in the right direction IMO. Air filters on dirt is a controversial subject. Like oils, the arguments are supported mostly by testimonials. Little real testing is available from anyone other than manufacturers, which are likely biased to their benefit. Dirt racers need to be, regardless of their filter choices, relentless air filter cleaners and changers.
I am a dirt guy, I change or clean air filters about every 2 hours of run time, less if it works out that way. There is benefit in pre-filtering or filtering in stages or drawing from a cleaner source air if it can be found. I have seen some interesting fresh air draw locations. Some other things to consider: Dirt is heavy and effected by gravity and time. The finer the filtration the more restricted the air flow path and the sooner the filter will clog or be overcome. The greater the filter area the more air and filter holding capacity for a given filter media type.
On the MC side, Pro MX racers universally run foam filters. On the FT side, Pro FT racers universally run pleated gauze filters with a pre-filter sock. Both are using oil on their filters. Both are as stated, relentless filter changers.

[englertracing]

Knn is the worst filter for dirt......

But K&N was designed for dirt(desert) racing and some feel it is by far the best for both filtration and minimal restriction...

They pass fines like nobodys business.
On titanium valved motocross bikes you get to change your valves and do a valve job twice a season Vs once or going multiple seasons with foam filters.
All 2 strokers know the knn silt means death to their bottom ends.

[ptuomov]

I have an idea and a question.

The question is that if you stack paper, oiled foam etc filters, in which order should you stack them? Which needs the most area and which filters only large particles?

The idea is to create a large air box base that draws the air up from a high pressure area at the front of the car. Then make the base thru which the air is drawn from the air oil separator multitwister plate. Make it large. As long as velocity doesn’t go too high, large dirt particles drop down.

[ZIGGY]

We touched on this subject in at least one thread several years ago, and there was no consensus then either IIRC.
(BTW the OP did not mention sealing the filter housing hold down stud, assuming its use, with a grommet or tight rubber washer,)
Regardless, my experience has been that on a track where the dust is really fine & dry, like talc, an oiled K&N WILL pass dirt. I don't recall
ever seeing or trying one dry on dirt. I will do that soon. IME R2C's are marginally better but no cigar. (Didn't they go out of business for a while or change hands?) Outerwears are good for stopping the clods. I've probably got half-dozen in different colors . I think the cycle and awd guys have the best materials.

[JDR Performance]

Most people have gone to Wix or Napa paper filters with a thin layer of grease on the top and bottom to stop anything from getting past imperfections in the lid, base, or filter. Run it for a night, replace it.

[JDR Performance]

Make sure it's sealed around the stud too. That is oftentimes overlooked.