Universal air filter sizing
 

This is my first car with a universal air filter and I noticed it was pretty nasty. I pulled it off to look for a size or something on it and found nothing. Grabbed a caliper to measure and the intake was 2.5 inches, checked the filter and it had expanded to 3 inches. Is this normal? The collar(?) on the air filter is pretty stretchy, I put it back on and the fastener stretched it down, there aren’t any gaps or anything.

I would like to have another dual cone type, but haven’t found one in 2.5. Wondering if it’s normal for them to be compressed like that? Three inch ones seem abundant.

Sorry for the silly question, but thanks for any help.

I would think the filter's mounting inside diameter would have to be just an rch larger in order to slide over a metal inlet pipe. Have you looked on K&N's website to see if they have anything that would accommodate you?

I personally prefer the original inlet setup as it draws cold air from the outside into the filter rather than relying on drawing in hot air from the engine bay.

It was universal when I got it. Just installed a Koyo radiator and the stock plastic duct doesn’t fit any longer. I need to get one of those panels I guess.
As to the filter, I ordered an AEM that has decent length flange off it and that is 2.75. Thinking the long flange will give more flexibility. I will see how the worm gear clamp seals it. It’s smaller than what came off, so i’m guessing it will be good for the now.

Sounds like it should he good to go. Anything you can do to seal the open filter from the hot engine bay is a good idea. Drawing in a bunch of hot air is not great for volumetric efficiency.

Noted. Currently looking into ducting. Hoping to not have to go front mount, but planning ahead. Getting cold air to the intake is included in that. Maybe intake ducting alone would be good practice.