How do I choose the proper diameter throttle body for my application?
Think of your engine as a big air pump. The more air and fuel introduced into the cylinders for combustion, the more horsepower the engine will make. (This is true only when other items such as the intake manifold, exhaust, and camshaft are also sized properly). Vehicle manufacturers normally undersize the OEM throttle body slightly to maximize low-end throttle response, so an upgrade to the next largest size--from 500 cfm to 600 cfm, for example-- will normally net 6-10 more horsepower.