Hello, I am working on building some intake manifolds for an I4 2.0L street car project. The engine is being built for maximum power output, using a larger turbocharger. My basic plan was a log style, tapered plenum manifold, as you can see here: http://www.xmission.com/~eblais/intakemani/20vintakemani.jpg http://www.xmission.com/~eblais/intakemani/20vintakemani2.jpg http://www.xmission.com/~eblais/intakemani/20vintakemani3.jpg This uses very short runners (4" in that version) which weld to a european "shorty" manifold cast aluminum piece which has a runner length of approximatly 3" and incorperates the fuel injector seats and mounts etc. Because i'm using that european shorty piece, the ID of the bottom of the runners is already set at approximatly 40mm, it could change slightly but pretty much defined by the casting. My question is this... where can i find information on various inlet bell or runner designs? What you see there is a slightly tapered runner with a 180 degree curve lip on the top. However i have seen some runners which have a much more gradual curve as seen here... http://www.dtafast.co.uk/jenvey/drawings/AH_Al.gif I think i'm probably splitting hairs here but am trying to find out what the absolute ideal design would be for maximum power. A broad powerband is not a huge concern as the engine will be drag raced and kept in a very narrow powerband between 6000 and 8000 rpm. Also really trying to figure out some guidelines to determine the shape... I see a lot of talk of diameter and length odviously, but am having trouble finding this.