I am trying to decide on an air filter for my cold air set up. I know everyone on this forum says for the short ram get the tried and true ru-3530. I also read that it doesn�t fit properly on the MAF adaptor (with out cranking it down). Thinking to my self and seeing the K&N makes a ton of different filters, there has to be one that fits better and has very similar surface area. I went thru some calculations and found that the surface area of the ru-3530 (tapered cylinder) is about 114.83 in^2. The next filter that is now being recommended more is the ru-1785 (straight cylinder), this filter has a surface area of 133.51 in^2. Assuming someone did the flow calculations to prove these filters will be able to flow enough for our engines I am comparing filters to similar surface area and just different flange sizes.
I think that some MAF adaptors are larger then 3 inches but I do know the one that came with my GMK CAI and eBay ones are 3 inches.
Starting with 3 inch I.D. flanges you have:
Straight cylinder:
RC-2530 has a surface area of 141.37 in^2 (metal)
RD-1300 has a surface area of 131.95 in^2 (metal)
RU-9004 has a surface area of 131.95 in^2 (rubber)
Tapered cylinder:
RC-4690 has a surface area of 116.80 in^2 (metal)
RE-0910 has a surface area or 126.72 in^2 (rubber)
RE-0810 has a surface area of 141.22 in^2 (rubber)
There are also many more choices; these are just examples of what might fit better depending on your flange size. If someone would like to know the surface area of a certain filter PM me with the part number or the dimensions and I can do the calculations and get back to.
