Hey wes.
My stock intake runners are only 170 mm long which means about 6.5 ". And I'm rememberig that diameter of runners were quite close to 35 mm (1,35").
And then to simulation engine of my program. This isn't based on facts but I believe that program uses Helmholtz theory, standard formulas for wave calculations. Program uses the plenum volume but does not take into account the shape of plenum. So I'm guessing it just assums that there are no sharp edges or something. But on the otherhand I haven't yet ffound reliable information about how the plenum shape would affect to whole package. I have thougth that it's more important to have correct volume than some special shape because the volume inside the plenum stil is on the most important role considering the waves and reflections and pulses that are moving and facing each other inside the plenum.
At this moment it seems that I will have about 400 mm (15,4") long runners and at the same time as I attach my new intake I will have to do some head work because it seems that headwork will significantly improve the power at higher rpms. And I'm talking only making the head to flow better from intake side not to grind much material out of it. To make it as god as some race heads are would be the best.
If doing only the head work or only the intake it won't give you not nearly as much pleasure. But combined effect with both of these mods will give you significant boost.
I'll post you later some simulated dyno pics.
- No-Pain -