Helmholtz resonator??? Intake manifold design Hi guys, I'm doing a bit of research into engine intake manifolds. The information I've found so far looks staright forward, but it's given out by turners and cottage industry designers, rather than engineers or physicists, so it's basic. I understand the fact that air will stack at the valve when it closes and the reflected columns will ocsillate up and down the intake runners until the valve opens. The issue I have is that there are various runner length formulas that calculate the resultant length based on an assumption that there will be a clear reflection from inside the plenum. Now I'm no PhD, but clearly the air leaving the runner trumpet will slow down by virtue of the venturi effect then carry on to the roof of the plenum at the lowwer speed. Then it will be reflected from the concave roof which will not have a clean reflection. Infact I would expect it to be rather turbulant, seeing as air will be flowing from a side direction as well from the intake. So after all this, what's left of the returning wave of air will then enter the runner venturi and accelerate, but now with a altered volume, velocity and wave characteristics etc. None of these issues are taken into account by the basic principals of the intake design formulas I've seen. Now, seeing as intake design seems of be more art than science, I'm not sure what I'm asking really. Basically, if anyone has any more advanced knowledge of intake design and could point me in the right direction for further research, then that would be most helpful. Thanks for your help.