Hi. I checked my air filter that looked dirty and after washing it 2 times in special K&N liquid it still leaves dirt when I run my finger over it... So I thought that maybe better solution would be to replace it. It has no mark on it or even serial number, so I measured it and send to some companies I know. Everyone said that they never saw filter of those dimensions before so I guess I wont get it.

Will it have any impact on my engine tune if I replace my air filter for smaller one? Or maybe getting bigger one is better idea? One that I have is pretty big. It sits on 3.54 in pipe with 7.87 in of filter length and width of 6.29 in thickest point and 5.11 in thinnest. With this rubber adaptor the total length of filter is 9.44 in. This is how it looked before cleaning:



I want to use it while looking for new one but I'm not even sure if it's dry or oiled type Should I oil it?

 

Too much oil can mess with your MAF sensor. I prefer a good dry filter (which one can argue filters better). You can match your size (as close as can be) on the AFE website. Only the pipe really needs to be 100% match as it needs to seal there.

Advanced FLOW Engineering | aFe POWER

 

I searched all internet, mailed one hundred companies and NOBODY saw or heard about filter with that dimensions that I need Probably this filter was made especially in one piece for my car in the light of the full moon on the slope of Mount Fuji. Anyway, I need to find something similar, and from my calculations the most similar filter has a smaller side surface by 59 cm2 (9.14 square inches).

Will this change be big enough to cause harm on engine performance?

 

many filters come with adjustable flanges. how about this one
https://a.co/d/2f4YZ34

or just search this on amazon if the link wont work

High Performance Universal Clamp-on Cone Air Filter 4“ Flange, fit Flange ID 3" Air filter/Flange ID 3.5" Air filter, Height 9" (230 mm), Top 4.65" (118 mm), Base 6" (118 mm), Red

 

Flange isn't a problem, most of manufacturers makes different sizes for one model. The bigger problem is the space I have for installing the filter - 200 mm of height is max



As I mentioned before I cannot find air filter with exact same dimensions. There are thinner, larger but not exact same. I assumed that only solution will be to find filter of same lateral surface area, then it will be just like mine, but with different dimensions. I found equation for lateral surface of truncated cone:

lateral surface = π × (R + r) × s

where:
s = √((R - r)² + h²)


My filter

r - 65 mm
R - 75 mm
h - 200 mm

lateral surface = 880 cm2

The most similar filter I found




r - 55 mm
R - 75 mm
h - 200 mm

lateral surface = 821 cm2

So I lose 59 cm2 by using most similar filter.


.. but then I found that type of filter with open front



I cannot calculate this one if it's cone inside the cone but I think the purpose of such a construction is to increase surface area without increasing the size of filter? I think that would be best solution, what do you think?

 

you already have more space than most people
mine is 4.5 flange and is quite common

 

Just match the pipe diameter connection correctly, and choose the largest AFE dry filter that will fit in that space. I think you are over thinking this....

Jam the biggest that will fit....

LIKE THIS!!!
LOL

 

lol this filter is the size of a KFC bucket

 

It fits just fine! Here is a pic of the test fitment using my kids play-dough to see if it hits the hood... which it cleared (play-dough remained turd shaped after closing hood)....

 

This is the best measurement method I have ever heard of! I don't have kids but I used my dog's turd instead and it fits perfectly! Thanks!