Anyone build their own Intake Manifold?
 

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. http://www.jeffgst.com/sitebuilderco...scrkbottom.jpg 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: http://www.fuzionetics.com/ebay/new/MFCV9295_5.jpg
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.

Re: Anyone build their own Intake Manifold?
 

i got a few feet of 3".

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

Re: Anyone build their own Intake Manifold?
 

I've never seen an oem manifold crack. Just port it out and call it a day you ------- trick ass bitch. :6

Re: Anyone build their own Intake Manifold?
 

^^^ Always so well spoken ;)

Re: Anyone build their own Intake Manifold?
 

I only speak the truth my son. :6

Re: Anyone build their own Intake Manifold?
 

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.

Re: Anyone build their own Intake Manifold?
 

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. ::)

Re: Anyone build their own Intake Manifold?
 

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

Re: Anyone build their own Intake Manifold?
 

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.

Re: Anyone build their own Intake Manifold?
 

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

Re: Anyone build their own Intake Manifold?
 

Thanks for the link! It'd be nice if they sold a 2.5" stack though. I think that I need to have a 2.25" tube where it meets the head flange. But I want it to be a little larger coming out of the IM so I can have it taper down to 2.25" gradually all the way to the head flange.

I did find these stacks for pretty cheap, but I'll have to contact them because they don't mention the material it's made of, or the length.

http://216.120.227.145/~racings//prod_velocitystack.php

they are sold at Auto Barn for $23 which is the best price I've found yet.

http://www.archcartpro.com/users/aut...ELOCITY+STACKS

EDIT: Just found them here for even cheaper. http://turbofriendly.com/velocity.html

Re: Anyone build their own Intake Manifold?
 

What size is the stock runner on a DSM intake mani?You going to weld to the stock flange just lop the runners off or buy make a new flange?Mike Weir can probably cut you a flange he is the man for that O0 Is there a benefit to coming out of the intake mani large and tapering down vs just one size the whole way i dont know just asking?I think you want the total volume of plenum and runners to be 2-3 times the displecement but that is just a guess.

Re: Anyone build their own Intake Manifold?
 

Too much reading,now my head hurts

Re: Anyone build their own Intake Manifold?
 

just throwing some parts to gether to make an intake mani isnt a great idea. sure longer runners are better for down low, and big runners are for top end but it is more than just a general statement. there are a lot of things to consider,like, how big can you make the runners w/out sacrificing too much velocity??


there is more to manifolds than just runners and a plenum.

Re: Anyone build their own Intake Manifold?
 

What you should do is look at a stock piece and analyze it while thinking about the objectives of the engine. Like if you have a high revving motor like a B16B you look at the IM design and compare it to a B20 IM. This is just an example, but you get the idea. From there I would go about modifying a stock IM to preserve an OEM look while getting the performance edge a performance IM would give.

Re: Anyone build their own Intake Manifold?
 

IMO, your IM isn't the problem with power dropping off. What size turbo do you have? (FYI, big 16g, isn't "big.") Also, what cams are you running? Tubular or are your still on the crappy log manifold?

Re: Anyone build their own Intake Manifold?
 

http://www.mne.psu.edu/me415/fall05/SAE/intake.html

http://www.dune-buggy.com/turbo/intake.htm

I believe I have some .pdf articles too, if i do I'll pass them on to ya. IF you don't have/cant find some more math formulas I should have them.

Is choping off the stock plenum and welding a larger one on an option? You could add a larger TB of you choice, the runners could be shortened and you know the injectors are at somewhat of a "good" angle.

Re: Anyone build their own Intake Manifold?
 

There are alot of routes to go with manifold work. Plenum volume and velocity are issues that need to be addressed. Really ported properly factory units atleast in the Honda world own most of the stuff out there. My dual throttle body manifold for my b20 is almost done. Naturally asspirateddd junk

Re: Anyone build their own Intake Manifold?
 

This might help https://www.homemadeturbo.com/forum/...?topic=85979.0

Re: Anyone build their own Intake Manifold?
 

Hence the reason I started this. I don't want to just slap together parts. I want to build it myself, yet get some input on some "rights and wrongs" before I do it so that it ends up being worth my time.

In the DSM world, the stock IM is decent until you get into the higher RPM's. Some people have them extrude honed, but for the money that it costs to get it done, an aftermarket SMIM seems the way to go. The runners are just too long, and the plenum too small. Otherwise I'd be all about keeping the stocker.

Right now I'm on a 50 trim setup with the stock manifold at around 26psi. Cams are HKS 272's. But this winter the setup is changing over to an SLS tubular manifold, with an S362 hanging off it. I'm hoping to be flowing right around 60lbs/min with the new turbo, and the stock IM is going to be somewhere that is definately going to need some attention.


Thanks for all the links though, I will be digging through them all!

Re: Anyone build their own Intake Manifold?
 

Austin, btw the injectors on a dsm go straight into the head, not the intake manifold. So one less thing to worry about. But as for chopping apart the stocker, I guess I'd really like to just make a complete one instead of hacking anything apart. The only thing I would consider hacking off it the TB flange, and the head flange, but that's only if I find those flanges to be stupid expensive for new ones.

Re: Anyone build their own Intake Manifold?
 

Also I've been finding tthourhat as far as runner length tuning goes, it's much less involved in a FI setup then in a NA setup. In a NA setup you want to calculate the lengths based on the pulse created by the intake valve. While on a FI setup it isn't nearly as important. So those helmzholtz equations and what not for determining when the pulse will arrive back at the intake valve, really aren't needed to much in a boost application.

As for runner tapering. The reason I heard to do it is because it increases velocity of the air. The air on the edges touching the walls will move slower because of the friction, so you taper the runners to help speed it all up. Again from reading it would appear a 2-3* taper is ideal. My problem is, I have no clue how to calculate that. If I have a 7" length of 2.5" pipe, tapering to 2.25", what degree of taper is that?

Re: Anyone build their own Intake Manifold?
 

don't do a box plenum... hand form it into the shape you want to get the best/even flow to all runners. too many homebrew manifolds (including my first attempt) are built without flow equalization in mind. i have an idea for my next manifold, but it will probably be a couple years before i get a chance to build it.

Re: Anyone build their own Intake Manifold?
 

ITB's FTW!

Re: Anyone build their own Intake Manifold?
 

What A/R is the exhaust side? If its .48, i'd be willing to bet that your problem. D-series run out of room about 350whp on .48, .63 is much better suited as it creates quite a bit less exhaust reversion effectively extending the powerband. I'm sure switching to a tubular would help quite a bit too though. Whats your power numbers look like right now? 272's will help alot when it comes to making power past 7k as well.

Re: Anyone build their own Intake Manifold?
 

I know plenty about my car, it's setup, and it's strengths and weaknesses. I didn't just wake up last week and slap random parts on a car I know nothing about, which is what you seem to be insinuating here.

What I am interested in, is hearing any other advice on making my own intake manifold. I have a few different designs in mind. All of them being pretty simple. The main jist being slightly larger plenum, and tapered 6-7" runners. Just want to figure out the shape I want to make the plenum, keep it simple and cheap and minimal amount of welds.

Thanks for everyones input. It'll be months before I actually get it built since I travel a ton with my job, but I'll post up pics of it when I'm done.

Re: Anyone build their own Intake Manifold?
 

Re: Anyone build their own Intake Manifold?
 

Hardly. IDK, we'll see but I think you may be unpleasantly surprised with the results of a custom IM. Slower spool, and no effect on extending power although you probably will see in increase in power. Not exactly the results you (expressed you were) looking for. Sorry thats the way you received my constructive criticism.

Re: Anyone build their own Intake Manifold?
 

You're saying a SMIM won't move my power band right? And won't help me maintain my power levels at the higher RPM's? OK you're advice is noted, but I completely disagree.

But again I don't care what you think about my car, I'm looking for input on making my manifold. I've gotten a couple good links, and talked with some people, and I think I have a good idea of what I'd like to do now. I will hopefully have it done sometime in December, and will put up pics showing how I did it. Thanks all!

Re: Anyone build their own Intake Manifold?
 

Here is mine, I just made what ever would fit :y This motor never came efi so it had to be a diy
http://www.eville140.com/plugs/bigplenum.jpg

Re: Anyone build their own Intake Manifold?
 

this is old, but i saw a cool ass intake made from a spearco intercooler endtank, apparently you just by one end tank and it is already shaped and has a opening at the end, looked good to me. like this but it was cast alum, http://www.roadraceengineering.com/p...tank-17-lt.jpg

Re: Anyone build their own Intake Manifold?
 

That's a sweet idea, as long as the endtank has plenty of volume to act as a intake manifold plenum. Anyone know any decent and cheap end tank suppliers other than treadstone?

Re: Anyone build their own Intake Manifold?
 

here is mine that corey and i made (mostly corey). we made the calculations for the runner size out of a efi tuning book tyler had. had a whole chapter on intake manifold fabrication. its got vstacks, 9" runners, and a ls1 75mm tb

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Re: Anyone build their own Intake Manifold?
 

^ that looks good :6

Re: Anyone build their own Intake Manifold?
 

can you post of the formulas you used or the title of the book maybe?

Was it called Herllmholtz tuning or something like that?

Looks like good fab and should work nicely.

Re: Anyone build their own Intake Manifold?
 

I'm curious as to why the v-stack would be any different than a standard convergent design from plenum to runners?

Re: Anyone build their own Intake Manifold?
 

It has to do with the S type motion for better flow.
I don't know exactly why but thats all I could find on the subject.

Re: Anyone build their own Intake Manifold?
 

Where'd you get those velocity stacks? I've been reading around, and people are using measuring cups, metal egg trays, all sorts of crazy cheap crap that you can find in walmart for velocity stacks.

Re: Anyone build their own Intake Manifold?
 

I made one for a guy a while back, it's on a 2l Golf X-flow motor the guy used on an ovals track racecar....

https://farm3.static.flickr.com/2102...058b7b88b6.jpg
https://farm3.static.flickr.com/2184...19743569c6.jpg
https://farm3.static.flickr.com/2138...de4e8f3e90.jpg
https://farm3.static.flickr.com/2181...6f339140ff.jpg
https://farm3.static.flickr.com/2420...ed136700f6.jpg

Re: Anyone build their own Intake Manifold?
 

so ARE these better for flow than the runners being flush? i mean, it looks to me like they would screw up the flow cause they are sticking up halfway to the top of the mani..or does it have something to do with the #4 runner not getting enough air?