[The Former PFR]

Originally Posted by Doc1

My design allows for different length velocity stacks that screw on. The stacks that I will be using will actually sit on the floor of the plenum for turbo applications. With different velocity stack lengths that are interchangeable, one can tune a N/A car for hp and torque at specific rpm levels. It also helps the head porter so that he can easily take the stacks off and port match the runners with the heads. Unlike other company designs, the outside runners start out as oval to match the heads and flare out to a much larger round design that attach to the plenum to create a funnel effect for the air to travel into the cylinder heads. IMO my runner design works better than a straight oval or straight round design but that is only my oppinion. Actually I talked this over with a couple of fluid and thermal dynamic engineers. As far as I know, I'm the only one with a billet design- no welds here buddy. Everyone else uses welded sheet metal. It took my machinest 3 days to do the bottom piece. He said it would take another 1 or so to do the top piece. I wanted to get manifolds from other companies but they told me it would take 6-8 weeks at least. For me to make a replica it would only take less than one week in the cnc machine. And as long as I have the base program, I can make changes on the fly. If I wanted to I can design my fuel rails as part of my top piece cover and when the cover bolts down, it will also be bolting down the rails as well. This is my little pet project. Everything is based on theory but I am going to give it a try. I'm looking to do some R&D against a stock manifold and just see how it goes. It is ~3x the volume as the stock one and by using a 105 mm tb with 5" intake piping, it should flow alot of air through the top mount 91 mm turbos sitting on top of the hood.

While screw in runners may be very nice for NA applications, you really do need to watch. I very strongly predict that given the limited height in a Viper application, you are going to see a lot of flow reducing turbulence caused by the trumpets sticking out like they do. This will of course cause uneven air to fuel. Only making it and testing it will bear this out, but if I were you, I would have individual O2 or EGT's in every runner for testing. However, it is nice to see a plenum for NA performance. I know that's Mitech's is a turbo specific plenum, although it would work well for high revving NA as well.

As far as funneling air down into the engine, I think you will find this to yield little or no improvement...quite possible detrimental effects actually. Causing the air to change shape, and more importantly volume when at a high reynolds number will most likely cause a choking in the throat which will cause the flow to back up and become more turbulent. This will reduce flow and cause the air to heat up more. When given the opportunity, it is generally best to keep your pipe in a short runner the same cross sectional shape as long as the material is super smooth (which it should be). Fluid dynamics are hard to predict and unless your engineers ran CFD, the only way to know for sure is to test it. It sounds like you are going to do just that.

I like the billet idea, I just think it is gonna cost a metic ass ton and end up eating bits and wasting a huge amount of material. However, if you have access to it and have good recycling programs in place, go for it.

Good luck. I anxiously await the results. You should CNC a straight runner and flow bench them both. It would be easy to do and take away the guessing.