Originally Posted by Big Will 85
Say on a 2 litre, 4 cylinder engine you had a plenum with a narrowest diameter of 56mm on the entry - and it couldn't be opened out any more...
At what power would it 'cap' at?
It's going to be a bit of a restriction at 500bhp, you'd be better off with a 60mm one. You'd be seeing gas velocities in excess of 500ft/sec with the 56, and ideally you want to keep it 350 ish. It depends on so many things. Ultimately yes, you could do it, if you had a turbo big enough to push it through.