Originally Posted by Bosch-Man
...Reyland answer the actual question...why have bigger than 50mm all the way thru..or dont you know?...
I just told you above phil, its resistive, so for top end flow the fewer small sections you have the better.
The other thing people forget is that changes in diameter are as important as the size itself, so if you have a 60mm inlet pipe and stupidly put a 90mm throttle body on it then back to 60mm, it would result in less flow than 60mm all the way.