so i'm in the home stretch with acquiring parts and whatnot for my install, and one of the last things i need to do is get the manifold kit finished by a buddy of mine who's a pretty damn good welder.
My question is about the transition between the log and the turbo flange. I bought a JGS Stg II manifold kit some time ago, and since i am using a WRX turbo, i had them send me the kit with no flange, instead sourcing a turbo flange from a stock WRX uppipe. Now, it seems like most of the turbos people flange these manifolds for have rectangular turbine inlets, which works well with the rectangular radius plate they ship with the kit, as shown in the below picture:
JGS Stg II manifold kit
But on the WRX td04-13t, the turbine inlet is circular, as shown in the next pic (this is an updrade hybrid turbo, but it has a standard turbine side, from what i understand).
My question is whether i should even bother worrying about using a round section of pipe to connect the flange to the log or if i'm overthinking it and i should just use the rectangular plate and let the exhaust find its way into the turbine inlet's round opening. My gut tells me i should try and match the turbine inlet's dimension as much as possible, but again, i could be worrying about a flow difference small enough to not matter too much (since i have other factors working against me anyway with the log manifold in the first place).