Building custom intake.

interex · 05-17-2008, 04:42 AM

Okay... So I have this idea about building a custom intake manifold.
Before we get started let me state that I do work in a machine shop part time, I do know how to weld, and have done quite a bit of welding projects in the past. I also know that building a custom intake sounds easy but isnt exactly cake. Anyway I have this Idea about building a twin throttle-body SMIM. I'm not too sure about what size of TBs would be used or the size of the stacks needed to be used as this is just an idea and I've not really researched into it a whole lot yet. On the Chrysler 3.5L they run twin TBs and I think I could probably make something to do the same. Either the TBs sitting stacked or side/side. I took a few minutes to make a little drawing in GIMP to give a small idea... Anyway I intend to research this later and figure out just exactly what is in store for this project. I can make the flange if I have to but will probably just order one and go from there... I'll decide when I figure out what I'm going to do.

EagleTalonTim · 05-17-2008, 07:11 AM

I would be a little worried if the air flow on one side is more than the other side. Looks as though tuning would be a pain in the @$$. If you get it built and working, post some pics and some times in the 1/4.

90laserRSfwd · 05-17-2008, 07:24 AM

I'm not knocking you or your ability. I'm just going to put this out there for you. I know everyone likes to be different and all but I'm just wondering what you think the gain would be vrs. ordering a SMIM from on of our supporting venders? I'm not trying to shoot you down like I said before, just trying to understand why you would want to invest such a great deal of time, money, and effort into something like this?

Marcus92 · 05-17-2008, 08:00 AM

It would probably be more ideal to not run the air flow into cylinders that are right next to one another for airflow reasons. I would split them 1-3 and 2-4 would be one way you could do it. Probably also a better idea to run them stacked, not side by side because that would lengthen your outside one to an undesirable length probably making it harder to tune like someone previously said. Its a shame hood clearance is an issue or you could run one like the oldschool 80's turbo cars with the TB above the VC and you could have an equal length runner type setup using 2 tbs and then your Y pipe. Personally Sounds like alot of work for unknown gains.

interex · 05-17-2008, 09:02 AM

Hmm, Well I was thinking of a turbular intake manifold. using 2.67" (68mm) stainless steel. Doing it in a cross pattern would work also, like 1/3 and 2/4 having the same TB. I could stack them so there isnt a lot of extra flow required for the 2/4 ports, or even just a standard 1/2 and 3/4 being on the same TB. I know this is an exhaust header (at bottom) but I think the same concept could be put into making a twin-tb manifold for the 2.0L.

It wouldnt cost me very much at all to make it as we can do it all in the shop, the weld time wouldnt be that bad, and the material would probably just come from the shop. as for bending that would take a little time to get measured properly. And... a SMIM from the vendors are all very expensive and I'm a creative person so if I can do it, why not?

tkelly27 · 05-17-2008, 09:27 AM

What are you hoping for, benefit wise? I'm not under the impression you will see any over stock. Some reading about intake manifolds will explain the resonance theory behind the standard chambered design, and why you won't find an aftermarket equal length style. Also, dual throttle bodies, why? Synchronizing is not something I'm into. My gut feeling is that 2.5" would be too big for intake runners too.

Where were you planning on getting a SS intake manifold flange? TB flanges? You'd want at least 1/8th, if not 3/16" plate for those. I dunno, I think a mild steel intake manifold is a good, cheap, easy to make idea compared to aluminum. Thick SS is kind of like working with mild steel, welding wise, for me at least.

interex · 05-17-2008, 09:41 AM

I can make a manifold like Magnus easily. I just thought making a twin-TB intake manifold would help with air flow on an engine with an extremely ported head, with larger valves. I dunno was only having ideas. I might just make one like the Magnus one everyone talks about.

Black95awd · 05-17-2008, 09:46 AM

Quote:

Originally Posted by interex

I can make a manifold like Magnus easily. I just thought making a twin-TB intake manifold would help with air flow on an engine with an extremely ported head, with larger valves. I dunno was only having ideas. I might just make one like the Magnus one everyone talks about.

you are lacking plenum volume, and that it key.

tkelly27 · 05-17-2008, 10:34 AM

I wasn't trying to say you idea is bad, but there is good reason nearly all intake manifolds designed for making power have plenums.
http://www.carbodydesign.com/archive...-engine-lg.jpg
That is one instance where dual TB's are deemed required. Look up some other designs and it's mostly that style on V type configurations where the intake ports spaced out on two different axes. I'm of the opinion that the dual TB setup on those is to maintain plenum volume without having to resort to shapes that hurt flow.

There is a mazda or something like that, that has equal length tubular cast aluminum intake manifold. I don't know what the design intent is though, as you diminish the ability to do resonance tuning without significantly adding to the flow properties.

As you increase the area of a TB, the flow increase is nonlinear. The same reason a single 3" exhuast has comparable flow to dual 2.25" pipes. Cheap 70 and 75mm TB's are abound for mustangs. If you can make a magnus IM, you can make it fit a mustang TB.

interex · 05-17-2008, 12:40 PM

Hmm, Sounds like I'll just go with the standard Magnus style plenum/intake setup. I can make one that isnt the problem. The problem is making sure the stacks are the right size and that the taper??? to the end of the plenum is proper for my setup. I'll look up the specs if I can find them and see what I can do. I'll be sure to take pics of my work in progress IF I decide to go this route.

kenamond · 05-17-2008, 02:36 PM

There's a lot of R/D and testing in intake design. If you start with something brand new, you don't have any idea how it'll perform. I like your DIY attitude, but I'd think that you might just want to *copy* (yes copy) an existing SMIM and get the benefits of doing it yourself, saving money, but getting the R/D/testing benefits at the same time.

If you decide to go with 2 TBs, I'd think you'd want to pair (1,4) and (2,3) together, as these are 360* out of phase. If you pair things any other way, the TB has to flow air for two cylinders that somewhat overlap in timing. If you pair like the stock exhaust, each TB is only flowing for 1 cylinder at a time which would flow better for a given TB. But that's my gut feel.