My point was that higher CFM isn't a reliable indicator of superior boosted flow. The infamous 2JZ-GTE Supra factory twin turbo head needs no mods, not even a valve job, to produce 700 hp from 183" on high boost. The extremely similar (by flow and mean cross-sectional area) RB26, 7M, etc. are down by hundreds of hp under the same conditions.
Why is the GTE head so superior? Toyota doesn't know, the port locations were compromised to allow larger water jackets (the N/A GE head has better ports, but only NA). It was an accident.
,,That is very interesting and I did not know that.
I don't keep up with Japanese performance.
Id suspect it has something to do with the lack of low lift exhaust flow, port velocity, and cam profile.
