I kept it open to avoid sucking water in to the intake. Any water that got in to the box just sat at the bottom of it with the open concept, while still delievering cool air to the intake. A little water in the intake wont hurt, but in a rain storm you wont want suction down at bumper level. If your looking for a true ram air, I would do a hood scoop only for the reason you will get alot more volume of air. The max pipe you can really do is 3" from the bumper, and you could get alot more volume through a full sized hood scoop.