The outlet of the box will have a suedo v stack. The pictures may be confusing without a first person vantage point. Air will enter the box via the 4" v-stack. It will exit the box via a 3" v-stack post / in the filter. Shape of the filter isn't critical here, surface area is, and to be honest, if I ever do drive her in inclement weather I'd prefer the filter stay dry-ish. Hopefully this cut away gives better perspective. Besides the agressive look and "in yer face" factor, the black external v-stack will provide a smoothed contoured inlet into the box, and the V-stack or bellmouth filter should smooth the transition into the 12" of 3" pipe before the turbo inlet. Hope thats clear as mud LOL! Whatcha think Wicked?
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I suspected the filter may have had an internal stack(good ones generally do) but airflow to the stack is still disrupted....the filter material is always too close to the stack in them....that being said though, again, this is a turbo application and that type of thing makes very little difference when it comes to forced induction...the turbo doesn't really care, its still going to pull air however it can to maintain whatever the wastegate pressure is set to. Still, that filter may actually hit the magical 3/4" measurement if you are measuring from the apex....and the people who quote that number are never very clear whether they mean from the apex or the lip. It not like we are talking any significant power difference anyway, more of a theoretical optimum as applicable to NA engines.