I'm curious about how to select the appropriate throotle body size for any particular engine setup. I'm more interested in theory than in one specific setup, and I'm hoping to come away from this with knowledge that will help me no matter what setups I choose to run in the future.

When I searched for this info, some things that came up were revs, turbo vs. N/A, displacement, IM runner length, and quantity (4 ITB's) vs 1 with a quality design. There was also mention of a spoon TB that tapered 8mm - from a 70mm opening to a 62mm plate. Since noone seemed to be offering solid info an how to select a throttle body, I've come to you guys. Teach me what variables matter for this, and how to apply that knowledge.

 

Maybe I should simplify my question... How big is too big, and what problems does it cause?