I'm going to be putting a larger plenum on a dseries intake mani and I was just wondering what general size I should shoot for, I'm thinking about using 4" irrigation pipe then weld up a throttle body adapter. So far I've cut the runners to about 6" from the head flange. Also, what sensors/ coolant lines do I have to run? Like the coolant hose on the throttle body, can I just block this off? Thanks for the help, If all goes well I'm going to rape somebody on ebay with this.

 

That coolent line is for the EACV. I havent run coolent to my ZC since I put in on in Denver and never had any problem. You need to figure out a idle control system though. If you choose not to run a EACV prepare for shitty cold idle or high warm idle and for it to wonder with time as the throttle body clearence changes.

There are some references to plenem volume, I thin its roughly 1x the displacementfor FI. Dont hold me to that though. GOOGLE. If your doing Hemoltz resonator tuning you need to calculate it based of your runner legnth and target RPM peak.