Aluminium piping. Is it a mistake or not?

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Forerunner to V-Tec and VVT-i. The manifold is designed in such a way that a large butterfly valve in the surge tank can be used to emulate long or short runners as needed. Without it your power below 4000RPM takes a hit. MKIII and MKIV N/A's both have this system. Other 7M-GE equipped engines (such as that from the Cressida) do not have it and it's part of the reason they make less power.


EDIT: You could of course go with a completely custom FFIM with multiple runners and valving such as the manifolds BMW used with a couple of their newer inline 6's... you're going to need one hell of a crew to help you calculate and cut everything to the precise lengths needed though... If you tipped the engine a decent amount you could build something similar to the old BMW manifolds, but it'll have to be tipped further to still accommodate the stock ACIS valving. BMW M3