The intake runners are all tuned for max power at a certain rpm. This is based off of port timing and has nothing to do with the fact that only 2 runners may or may not be getting air full time. The stock primary and secondary intake runners on the S4 are an average of 1 in. difference in length between primary and secondary. None of them is quite equal length anyways. You can not tune 2 runners to 2500 rpm and then the other 2 to 7500 rpm and expect it to work properly. Again, look at the Renesis. When all of the ports are open the engine is tuned to its power peak. All of the runners are tuned to this point. The only reason that it has different intake runners is that each pair of ports has different timing durations and therefore runner length requirements. They all still tune for the same rpm though. When only 2 runners or 4 runners are open, those runners are still tuned for max power higher up in the power band. The fact that all of the air is flowing through a smaller area of ports though is what gives better low end power. In this case it is velocity over rpm tuning at low rpms. If you did tune the runners for max length at a lower rpm then yes power would go up there but would sacrifice up high. It has nothing to do with VDI even though the Renesis does have it. FWIW the S5 VDI manifold always has long intake runners. The runner lengths do not change. What does change is the distance that the reflected acoutic waves have to travel to get back to the other side. This is also how it works in the Renesis. The aux ports though are not affected by the VDI valve in the manifold. Their VDI gain comes from where the individual runners split up from the main aux runner. The idea is sound and does work. We have proof. The question is can we make it work in even a limited fashion on an older manifold? It is worth trying even if it fails.

 

reguardless of how long the runners are or how big they are in diameter this "idea" isnt going to change the max power about 2300 rpm. it will stay the same as if you never do this "idea" the 5/6th port and VDI would still open at the right rpm. To make a smooth transition from the ports being closed and then opening may be a problem. So the only change in power would be below 2300 rpm

but like i said before there was a small increase, nothing to jump up and down for but it may be just the much more if you want to get the most out an FC if i do get this to work.

Justin