I don't have a lot of space to work with in terms of filter height. It is looking like I'm going to have to go with some sort of K&N. Ran the calculations and it looks like both of these can flow enough air for 450-500 bhp, which is a good bit more than what I am going to be looking at.

http://store.knfilters.com/search/pr...x?Prod=RC-9480
http://www.knfilters.com/search/prod...Prod=RX-3900-1

One is just a regular cone filter and the other is the x-stream.

Any opinions? Thanks!

 

The RC9480 looks bigger and should flow more. Contact K&N and they can provide you with the flow rating for both.

 

Well after a bit of digging I was able to find a flow rating/area constant that k&n released some time ago and then was easily able to determine the surface area of the filters. Like I said, they both appear to flow more than enough for what I need, but I was just wondering if there were any issues with Xstream filters not holding up and wanting to cave in or something.

I'll give them a call either way.

 

Ok just got off the phone with them. Turns out they gave me much more conservative numbers. They said that for a 1.8L engine with around a 7800 RPM redline running a GT28RS at around 16 psi boost, the filter would need to flow approximately 510-520 cfm.

The filters listed above will do 349 and 458, respectively.

The only other one that they had that looked like it will fit is:

http://store.knfilters.com/search/pr...x?prod=ra-0990

Which will flow 520. However, it has an offset flange. Will this offset flange affect the linearity of air coming into the intake? That was the whole reason that the intake was adjusted was to get the MAF right behind the filter so that the air is more linear.

 

I have noticed too the smaller filters like that seem to get dirty much quicker. Before the turbo I would clean mine one a year or so it would start to turn black. Now, its every oil change. I have wondered if a larger filter would spread the dirt out more? lol

 

I'll happily clean my filter 3 or 4 times a year if need be. I just need to find one that will flow enough air!

 

You can only run what you can fit. 458 is in the ballpark anyways.
No the offset flange wont hurt air flow.

 

A b16 does not have a mass airflow sensor.

 

Nvm I read 16 psi and thought you were using a b16.

 

I swear...I see tons of pictures of Hondas on here running much larger turbos with itty bitty filters and have never heard of them complaining about not getting enough air. Am I missing something?

This is a Toyota 2zz-ge on a Lotus Exige.