I have a short ram air intake currently with an oiled Stillen filter (with a length of 6 inches), was thinking about changing it to a AEM dry flow when I noticed the available dimensions included different filter lengths without changing the flange diameter.

How do I tell which size air filter would be the best? I'm assuming that a larger filter would have less performance improvement and a small filter may not provide the needed airflow when required.

To make things more complicated, I remember seeing the following picture of infinimax96's intake below. It looks smaller in length then the stillen cone I have.

 

As long as the base of the filter where it clamps is the same outer diameter as the maf adapter or velocity stack you're using then it doesn't matter. If you go for a larger one, just make sure that it will fit in your engine bay.

 

It absolutely does matter ...

Regardless of the diameter of your intake tube, the volume of air that can be drawn is dictated by the volume of air that can pass through your filter element.

The volume of air that can pass through your filter element is dictated by the material used as the element (i.e. material flow) and it's surface area.

With most cone or panel filters advertised as "performance" filters, I'd imagine that the filter material would be at least as flowable as the OE paper material but the surface area is another matter.

Certainly don't use a filter element with a surface area that's less that an OE filter.

But ... point being ... the size does matter.

 

bigger and longer = better

 

If you're trans is auto, put the stock filter setup back in and say hello once again to the throttle response of the VQ.

 

Wonder why the need to rotate the battery 90 degrees in the photos.? Surely that short ram would of fit behind the battery as originally installed. Perhaps for air fow.?

 

Probably thinking the air would have a more direct, non-blocked path between the front of the car and the filter cone.