[shotgunslade]

There are a couple of issues going on in this thread. First of all, there is a significant difference between the intake path of a forced draft engine and that of an NA engine. On the WRX and the STI, the air filter is on the suction side of the turbo, so that any pressure drop, and resultant density drop in the intake air is overcome after the air passes through the turbo. In an NA intake, pressure drop results in a density decrease that is never overcome. So everything we can do to decrease pressure drop on the intake side increases the density of the intake air charge. Secondly, a major source of pressure drop on the intake side is involved in accelerating the air from rest to 7000 fpm, which is the velocity necessary to get 350 cfm across the MAF and through the snorkus. The trick is to convert that velocity pressure back into static pressure when the air charge hits the cylinder. This phenomenon is known as static regain. Unfortunately, it is never anywhere near perfect, and even in the best of circumstances, 60-70% is the best we can hope for. Why is this of interest. The reason is that the velocity pressure of 7000 fpm is 1.3 psi. That's how much pressure it takes to get the air up to speed to go through the intake system. This pressure drop converts linearly to a drop in density. So, if there were no static regain, given that atmospheric pressure is 14.7 psi, a pressure drop of 1.3 psi, would result in a density drop of 9% in the intake air charge. So, even with a static pressure regain of 60%, we still have a density decrease of 3.5%, and at 7000 fpm, friction and dynamic losses in even a short pathway are large, so i figure another 0.5 to 1 psi drop through the snorkus. So, there is something to be gained by decreasing both velocity and static pressure drop on the intake side.