Air Filters

[RichardNew]

Here's a recent article I wrote about air filters. Enjoy.



Richard Newton

[Reiver]

I can tell you why K&N won't tell you what filtration level they build to.....
I tried one of their filters, properly lubed/oiled and maintained, in dusty Az on my hot rod with a 4 barrel carb.
My idle jet would contsnatly get fouled/plugged with fine dust.
Switched to the same size paper medium filter and no issues.

[Ferrino]

Thanks for sharing. Very timely for me as I have been considering filters for my ITB project.

Sock type filters or screens affixed over the intake can help engine life but in most cases they will cause a small loss of power.

I can't speak for the sock-type filters, but my understanding is that the screen-type filters can cause significant losses at higher RPMs. One data-point I have is a 16% loss of power (albeit on a 8 KRPM peak power engine).

[Steve@Rennsport]

Whats lacking in the article is the distinction between the filtration requirements for street engines that should last 200K and for race engines which should last anywhere from 25 to 200 hours.

BIG difference.

[Reiver]

Originally Posted by Steve@Rennsport

Whats lacking in the article is the distinction between the filtration requirements for street engines that should last 200K and for race engines which should last anywhere from 25 to 200 hours.

BIG difference.

Weren't K&N's initially sold as race filters?
When I used one there was constant fine grit in the carb, you could see it. I tossed it after 30 days and two plugged idle jets.....no issues since. I was driving it quite a bit tho.
More flow seems to mean much less filtration in this case.

[airfix4]

Given filter surface area is constant, more filtration, i.e. lesser micron rating, equates to more restriction, i.e. less flow/potential power. Running no filter will always provide most power, but also highest engine wear.

In dusty areas where more filtration is needed, performance will be sacrificed, but engine life increased. These areas also cause filter to load quicker so replacement/cleaning more often is necessary.

It would be nice if the "cleanable" filter companies put differential pressure indicators on the filters to let the operator know how loaded they are. This is standard in the aerospace industry.

There is also a centricep, maintenance free, design which is interesting but debatable for turbines and not suited for IC engines.

[Steve@Rennsport]

Originally Posted by Reiver

Weren't K&N's initially sold as race filters?
When I used one there was constant fine grit in the carb, you could see it. I tossed it after 30 days and two plugged idle jets.....no issues since. I was driving it quite a bit tho.
More flow seems to mean much less filtration in this case.

Yep,..we use them on race cars only where engine life is not an issue. All the rest get OEM paper filters.

[82 SC]

On several other forums some of the conclusions were to keep the stock paper filter. Unless you have a all out race motor. A stock filter will do better in the long run and you can still do quite a bit of mods and use as a daily driver. Since I am a do it yourselfer/low budget guy I will stick with the stock filter due to the fact the motors cost more than my purchase price of my 1982!

[KTL]

Problem for a lot of folks is the K&N is the simplest & most effective way to go for Webers or PMOs, if you want to use the rain shields. The ITG filters are nice but if I run my car in the rain its going to ingest water. I suppose I could swap between the ITG and the K&N depending on the weather.......

Has anybody sourced a paper filter for the Webers yet? Last I saw, there was a suggestion to modify a round filter by cutting the exterior screen off of it. I did this with a Wix 42088 and it was a PITA to remove the screen and it doesn't re-shape itself into an oval all that well.