Josh’s bigger throttle bodies project

[jikemenkins]

When measuring the ID of the stock throttle body casting directly, the bores are roughly 30.5mm at the exit. When measuring the ID of the stock intake funnels, they taper to a minor diameter of ~25mm before beginning to taper open again, expanding to roughly 30.5mm.

After exploring several other Honda intake funnels and also some aftermarket options I determined that boring the ID of the stock funnels very nearly maximizes what is possible when attempting to increase intake cross-sectional area via different or modified intake funnels. Whether it be done via a sandpaper drum or flap-wheel, or more sophisticated methods, opening the stock intake funnels to roughly 30.5mm buys you all the intake area that you can possibly achieve with the stock throttle bodies.

To anyone who would attempt such a modification, be aware that at a 30.5mm ID bore, the walls of the stock intake funnels will taper down to ~1mm (.040") wall thickness.