But the exhaust is traveling at high rate of speed and will take the path of least resistance to the low pressure area of the expansion cone. The wastegate is shut on spool up and when it reaches full spool and the wastegate opens it is simply limiting the airflow through the turbo to keep from over boosting. The major flow that matters is what is going through the turbine wheel and it always has a direct path to the expansion pipe. In a open mouth pipe the turbulence is extreme. We have performed many different tests on the dyno and splitting vs. open is huge. I was surprised myself that removing the divider did not cause a bigger issue, but back to back testing with the 3 inch downpipes with and without the separator showed the same spool, removing fixed the issue of boost creep with breather mods.
