I picked things for my truck with performance and low noise in mind ... well, didn't think about noise when ordering AF1 ... performance blurred my view! The first few drives with the AF1 … noticed a power difference! That’s a good thing! The bad thing was it had an awful moan just before going open loop. Was like blowing air over a large bottle or drum. A deep nasty note that hurt the ears! A most uncomfortable tone.

Slid the air filter farther out on the end of the tube … Ah… much better! Most of that really awful sick moan gone … but still hits some of that deep bottle note at times. The bad tone was certainly less but would still hit the ears with just the right throttle … a little more or less and it would go away. The real problem was when that throttle position was what I needed to hold a given speed, usually just before the TQ would unlock … most noticeable when pulling a load and starting to throttle into and up a hill.

So, my thinking is that the end of the tube where the filter mounts is still catching the incoming air. The filter has a rounded funnel type flow as it tapers in to the mount flange. The tube is tapered in like a spinner pipe cut-off was run around to cut the tube off causing a slight edge bend inward on both sides. The slight taper in of the tube made it impossible to mount the filter right on the end because when the clamp tightened it would squeeze right off the rounded end. This means that the tube end sort of hangs an edge out/in inside the filter and catches air flow just right causing that blowing over a bottle tone.

To make this long story short … after many weeks of thinking about the sound and possibly trying a different setup etc… I borrowed a pipe expander and made the filter end of the tube flare just slightly out. While I was at it … I smoothed out both end edges and removed the other ding that I didn’t take out when I first installed. Now the filter mounts tightly on the tube end.

Also I took the rubber elbow off and cleaned up all the flappers and rough blobs it had inside. The rubber on the outside is sooo smooth and finished but the inside was rough and had a pretty good ridge where the two molds were put together. I trimmed stuff down to help make a smoother feel. While I did this with a razor blade and x-acto knife … it might be easier to use the end of a soldering iron to carefully melt the seams smooth? Didn’t think of that then!

Anyway, after all of this … I’ve been driving for a few days and cannot get that bad tone to happen anymore! It sounds SOOO much better! The BhaaaaWaa bottle effect is gone! Yes you can still hear some airflow but it just sounds all good now! You know how many talk about it sounding like old 4 barrel carbs opening up ... well, much of that sound is now gone. In my case ... the AF1 was louder than my exhaust and now it is a nice smooth matched balance.


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I shared this on another forum but I though I'd share it here too...