RESULTS ARE IN!
Subaru OEM Catless Up Pipe at 28" - 244.6 CFM
Grimmspeed Up Pipe at 28" - 292.6 CFM
CFM increase of 20% or 48 CFM at 28" of water
I am honestly quite shocked by the difference between the catless oem and an aftermarket up pipe. My initial thought was that the aftermarket version would flow better but not by this much. I can only imagine what the difference is between an aftermarket and a cat'd oem.
Remember, this isnt max flow, this is just the flow at the industry standard of 28" of water...it is used for comparison, not determining max flow.
Subaru OEM Catless Up Pipe
GrimmSpeed Up Pipe
Justin