Some people( at least one db comes to mind) are confusing AIR FLOW with AIR RESISTANCE.
Make your 90 degree to 45 degrees or less at the box. The straighter the better With the new bend so close to the entry point (external filter) the bend there will have very little, if any, effect. For a 1000cc engine, a 3" intake over such a short run is more than big enough to worry about materials. You could still get away with 2.5 inch, but never go smaller than factory as a rule of thumb. The sharp bends is what you need to eliminate.
I prefer a relatively massive K&N filter with the screen for this. My box is open both at the bottom and end with a smidge of filter showing. The screen keeps water spray/snow out so you can have the full effect of the filter with no water entry...something the UNI in the box may not stop.
Your factory roof plays a huge role in this too...those vents in the rear direct air downward to help with dust swirling up from behind. When enclosed with a windshield and back window, it is really important to keep this effect. Aftermarket roofs remove this effect so keep the air intake towards the side of the vehicle, not inside the bed area if ypu want to keep the cleaning down to a minimum.(Open machine then any location towards the front of the bed area is fine)
We get serious dust on strip mine cuts as well as coal dust which makes regular dust look appealing. If bad conditions or multi-day trips are in order and the dust starts overtaking the filter, with K&N you simply remove, take off screen, wash in a creek, dry with a towel, reinstall and ready to go.
I have appx. $200 in building everything but will never have to buy another filter again so it will pay for itself easily.
Where you ride dictates the amount of filtering you want...the internal UNI simply will not hold up to a days riding up here. Coal dust is hell!
If I don't know something I have no problem admitting it..but when im 100 percent on the know...well..
I did the math... .212.051 cu.in of non-mobile air volume..@4500 RPM it requires 64 CFM...easily handled with a 2.5 inch pipe, ID.... Expandable hoses with corrugated sides on a run less than 30 inches hurts NOTHING nor restricts any airflow...true mechanics only need to see that "hat" to know there is a lot less resistance without the in-up and over flow required by the factory set up. Not everyone has master ASE certs...which is why I came here. I'd hate to see someone miss out on an awesome setup because of misinformation.
