I have a set of hyabusa 46MM throttle bodies and plan on making my contribution to H-T DIY ITB's. I will be using 2" outside diameter aluminum runners. My biggest question would be how long to make the ITB's with velocity stacks? This will be used on a stock internal'd H22 hatch. Eventually cams will be in the future mods but for now stock internals. Now I have asked a number of people that have done some very nice DIY setups and my replies have been from 7 inches to 9 inches from flange to tip of the velocity stack. Any ideas? Any dyno proven results out there for DIY? also when tuning for harmonics (resonate tuning) which is the best harmonic to tune from? Also once the correct harmonic is tuned for, what RPM range would be the most beneficial to tune for (I would think around the 5000-6000 RPM range on a stock cammed H22)? Anyone have any formulas? Thanks.

 

anyone?

 

about 9-9.5" is what seems to be working best lately.