ju-on

I'm just wondering if anyone has any good links, or experience with building a cheap homemade intake manifold. As far as DSM's go, you really won't find a quality one with any kind of warantee for under $400 unless you buy something used. And we only have 2 cast options as far as I know. One of which I don't want, and the other which is over $500. So I have been looking around a little and have been considering just building my own. Seems like most the DSM Sheet Metal ones use some sort of rectangular plenum design. And it seems that the welds on the edges of the rectangle plenum are the most common cracking points. Some brands seem to crack more then others, but eitherway it seems this is the most common spot that they crack

So I was thinking of just using something like a 4" piece of pipe as the plenum, that way there are no edges that can crack like that. After digging around, I guess something kind of like the OBX ones I see on ebay for some honda applications:
Then just cutting 4 holes in the pipe for the runners. Using 4 pieces of pipe for the runners, and just crushing the ends in a vice until they are the correct shape to match the head ports. I am wondering though if there is an issue with using a round plenum because everyone else seems to use rectangular ones.

Seems pretty simple, but wondering if anyone has made one before and maybe has any pointers. Like how to decide the volume of the plenum. Do you want it to hold a similar volume to your motor? (ie a 2.0L motor so I should size the plenum so it holds appx 2L of air?). Also there are other things such as incorporating velocity stacks, or tapering the runners. I'm going cheap so I may not do either of those unless I can find some velocity stacks cheap, or find a way to taper my runners cheaply.

I'm thinking about making the first one out of mild steel until I get it how I want it. Then make it out of aluminum if I really want to.

Smith-02

i got a few feet of 3".

just ------- make the manifold and shut the ---- up

stillnoturbo

I've never seen an oem manifold crack. Just port it out and call it a day you ------- trick *** bitch.

imburne

^^^ Always so well spoken

stillnoturbo

I only speak the truth my son.

ju-on

Porting the OEM manifold isn't going to get me the results that I want. The plenum is too small, and the runners are too long. It's good for low/mid range, but starts to die in the upper RPM range which is where I want the power to be. I know I need a larger plenum, and shorter runners, but wanted to see if anyone out there just so happens to have a bunch of knowledge on sizing it all.

So before I just go build one and screw something up and waste money, I'd like to know if anyone has any good pointers on plenum sizing, or just the design in general before hand. I've dug through the DSM sites a bit, but people can be very close minded sometimes so I like to see what everone outside the DSM world is doing, and see what kind of pointers and ideas they've tried and had results with.

stillnoturbo

blah blah blah oem ain't cool and just want something bling-blangin'. Just get it extrude honed. It's a 4G so there is no upper RPM range.

jinxy

first one looks like it cracked because they were over zealous with the grinder and polishing. keep it raw and it will be fine.

ju-on

If you've seen pictures of my welds, you'd realise that if I was looking for bling then I'd just buy something. I kind of go by the saying "bigger the glob, the better the job". I don't think anything I've ever built turned out very pretty. And again, porting or extrude honing isn't going to get me what I'm looking for I don't think. But thanks anyway. As of now I'm only revving to about 7.5 because my power band starts dropping off. I'd like to be shifting closer to 8.5k, and I think it's my IM that's part of the reason my power dropping off, hence the reason I'm looking to upgrade. Just don't want to spend 400+ if I can whip something up on my own that works halfway decent.

As for that crack, those specific ones are always cracking on the seams there. So I'm not really sure what the deal is. I just figure I'll use a big old pipe for the plenum, so then there's less seams and welds for cracking to take place at.

Anyhow, doesn't sound like this was the best place to ask this. I was thinking maybe someone here had done this before, and knew of some cheap places to get stuff, or maybe just some pics of some other homemade ones to give me ideas, just some opinions from people who haven't been tainted by know it all DSMers that think there way is the only way. But that's fine, I'll just do it up on my own and post pics up when I get it done and show how I did it all.

90dx

I would just copy one of the common aftermarket intake manis for the DSM and work from that.Really you could build something for fairly cheap that would perform well maybe just not look as baller.Assuming you can weld alum hit up Rossmachine and grab some goodies.For calculations of plenum size vs displacement etc hit up the SAE papers or google i dont really have anything to add there im to lazy to know.Good luck post some results.

http://www.rossmachineracing.com/intakepartspage.html