Technical Theory : Plenum Design

[bszopi]

Ok, so I know we've discussed this before, but I have a welder now, so ideas have been coimg into my mind (while daydreaming in my boring ass classes...). We have talked before that longer runners means more torque. And more torque never hurt anyone. So, with that in mind, I think I have come up with a design that would lengthen the runners (of a 3400) by about 8-10". The plenum volume itself would remain about the same, if not somewhat larger. I'll try to get a drawing up within the next few days, but with the aforementioned ideas, what is everyone's thoughts?

[ikessky]

Sounds very interesting Brad. Would it affect hood clearance? Are you actually thinking about making a prototype?

[SappySE107]

Why not try a 2 stage setup then, because you are essentially adding low end at the cost of where the 3400 shines, up top. Probably good for an auto though so who knows. You will want to keep the plenum area for sure, and larger would be much better.

[bszopi]

Yes, I do plan on making a prototype. And if everything goes right, there won't be any hood clearance issues. I know that the coils will have to be relocated, but I think that's about it. We'll just have to see once I get a chance to start working on it. I'm gonna try to draw up a rough isometric sketch of it tonight. If I get it done, I'll scan it in and post it.

[ikessky]

Cool. Can't wait to see how this turns out!

[bszopi]

Here is a quick drawing that I did today to try to at least put across my thoughts...

[SappySE107]

Looks good, I just hope longer runners are going to do what you want. Im wondering what would happen if you used extra large runners up top to a bell mouth type opening on the lower. It would be a runner still but also sorta like a plenum volume.

[ikessky]

I see how you are planning it now. I couldn't get it that it was going to have longer runners but still maintain good hood clearance. I think if it was made right, it would definitely do what you are asking it to and would be a great conversation piece when you pop your hood!

[geoffinbc]

Looks like the 3.4L Camaro intake, in a way.

[bszopi]

Yeah, kind of modeled it off of that design. I have thought about making it just a box on the outside with the runners hidden inside. That way, some of the angles areas would add to the volume of the plenum itself. It would look plainer, but that might be an advantage. I dunno... we'll see what I can come up with once I actually start cutting sheet metal.

As far as the velocity stacks go, I have been thinking about that as well. In fact, I'm not 100% sure how I'm going to transition from the runners to the lower manifold. The easiest way to make the runners is rectangular tube steel, but going from a rectangle to a flat oval is going to be a very odd transition. I having been thinking of porting the lower manifold runners to rectangles at the top, transitioning to flat ovals into the runner. But I'm not sure if there is enough material there to do that. I need to look it that area more....

Anyone have ideas of what metal to use? I was thinking 1/8" mild steel, but not sure if that will be thick enough. Suggestions?

[geoffinbc]

ALuminum would be best. It is what all intakes are made from. Plus you can cut it with a chop saw or table saw.

But I guess your concern is the welding.

[SappySE107]

I wouldnt go sharp corners aka rectangles. At least not on any curves. Could you use the rectangle pipe and weld in the corners and then grind it down? Might make the transitions easier anyway. I just bought a lower off ebay but I dunno when Ill have it.

[bszopi]

Yeah, my concern is the welding. Otherwise I would be using aluminum.

I've found a few places that have flat oval tubing, but not sure on the size I need right now (haven't actually gone out and measured). Unfortunately, most of them are overseas, so I don't think it would be worth it. Some of the other ones are stainless, which I don't really want to pay for. I could probably get some J-bends, cut them down the center, then weld in a flat piece to connect them back together.

I dunno, gotta do some more research into the materials...

[geoffinbc]

What kind of welder are you using? Cuz MIG welder will weld aluminum

[bszopi]

Just a cheapy 90A Arc. Got it for $90 mainly just so I could mess around with and learn on. And its an AC, and from what I've seen, aluminum rods require a DC+ type welder (or maybe its DC- either way, I have an AC).