I am going to build a custom turbo manifold because it will be cheaper for me, i have a few questions. One is that the exhaust ports are oval but the manifold tubes are usually perfectly circle, so how do i go about that. The other is how big of tubing should i go and how thick should the tubing be. The story of why it is cheaper is because this guy i am painting cars for owns a welding shop and he said that i could mess around with building a manifold and downpipe if i wanted. So we already plan on making the plates that bolt up to the head and turbo by going off my header and my turbo that i have and cut them out of plates using a plasma cutter, but i dont know any specifics on anything else on the build. I have an eclipse turbo and what psi does the stock internal wastgate open at. Because if it is 6 or 7 then i will keep it. If anyone has links to websites or other forum topics that show the complete process, please put them up. And i tried searching but couldnt find anything.
The manifold that I built wasn’t equal length, but I did make my own so I will chime in. For the tubing I used schedule 40 stainless steel butt-end elbows. I got them from McMaster and they are around $4 or $5 each. I forget what the exact diameter of them is, but they are just big enough to fit over the eliptical exhaust ports. You will also need a short straight piece of the same material.
As far as the flanges go, I used 1/2" thick stainless, but we found that 3/8" would work fine. It’s pretty tough to cut through that stuff with a plasma cutter, and you’ll have to do tons of grinding to make the edges smooth, especially on the ports. What I did is get an exhaust manifold gasket and a turbo gasket and scanned them into a CAD program, made the CAD drawing, and then CNC machined them. They came out gorgeous, but I’m sure most people don’t have access to a CNC. I’m sure the plasma cutter will be fine if you’re carefull and anal enough to make them perfect. You may even be able to do it on a manual mill if you have access to one. The plasma cutter will really come in handy for cutting the elbows into the odd shapes you’ll need to make the collector and runners.
We started by first making the collector, which involves a lot of cutting into weird shapes to make it all work. Then we used a jig to make sure that it would place the turbo where we wanted it, and just started cutting and tacking to get the runners to line up to the collector. If you go with stainless, which I highly recommend, it will definitely have to be TIG welded, and I would even say that you should TIG it no matter what the material is so that you know you’re getting good penetration and a good strong bond.
As far as the turbo, if it’s a 14b (off of a first gen 5 spd) then the wastegate spring is around 9-10 psi.
Hope this all helps. Feel free to ask more if you need any help. Be careful with the heat when welding onto the flanges or you’ll have major warping problems and it won’t seal tight to the head or turbo!
so are the pipes eliptical or circle, and if they are a circle then do you leave a lip on the inside where the pipes meet the plate that bolts up to the head?
The pipes are circular, but they are large enough to completely cover the exhaust port. I am not sure what you mean by leaving a lip though. Go to www.mcmastercarr.com and enter this product number: 45605K515. I’m not sure if that is the right diameter, but it seems pretty close. Just measure the widest part of the exhaust port and get whatever is closest to that measurement.
what i mean by lip is that it doesnt go smoothly from the plate to the pipe, leaving a lip on the inside
You don’t need a lip or anything. Just put the pipe flat to the flange where you want it and weld.
Please, post pictures of your progress I always like seeing people make their own parts, Im sure there are others that would like to see it as well. good luck making a manifold isnt easy
It will be a few weeks for pictures because i need to rebuild my engine really bad. It crossed the 190000 mile mark this morning and it eats oil like it is nothing, 3 days ago my oil was full and i checked it today and you couldnt see it with the dipstick, so that comes first then i will buy the piping. And could i just get the piping for the manifold from my local napa or something, because if i can then that is why i wanted to get specs on all of it. And could someone tell me how many of what bends i need for the manifold and the downpipe. I want a manifold where 1&2 ports go to one side and 3&4 go to the other, do you guys know what i am talking about? I think people call them ram horns? Dont flame me if that is wrong because i never gave a shit about turbos really until i finally got the turbo and intercooler.
yea a ram horn
just keep us posted~!
thats exactly what i wanted and that is what i am going to go off of, thanks bro
I’m not sure if you’ll be able to get the material for the manifold at NAPA. They aren’t just exhaust piping. Shitty manifold companies like SSAutochrome use exhaust piping for their manifolds, and that’s why they suck and break so much. You really should use the schedule 40 stuff i showed you. Most local parts stores also won’t carry any exhaust stuff in 2 1/2 inch or 3 inch which is what you’ll need for you downpipe. If they happen to then it will most likely be expensive. JC Whitney was the best I found for U-bends.
like he said unless, like we have all seen and is damn time consumming making “mandrel” bends from a straight pipe. using a chop saw to cut small angled pieces and arrange them into bends( like a circular pizza, the pieces can be flopped around to form different arrangements)
and a straight piece of 3" piping for your down pipe could be scored at most any exhaust shop let them know the reason why and more often than not they will just give it to you.
You can buy mandrel bends all over the place for not too much. However, making a downpipe to fit properly and put the exhaust where you want it is very time consuming. It’s worth having a shop do it if the price is right.
One more thing to add about the manifold. Most ramhorns aren’t equal length, and to gain the advantages of an equal length, the runners have to be within a tiny fraction of the same length as each other, which is near impossible unless you have a lot of experience. I calculated some flow equations when I didn mine and realized trying to do an equal length was too much of a hassel.
i dont really care if it is perfectly equal length, i just wanted them to be closeer than the ones that normally come in turbo kits, i dont like those and also they sit to high so it wont work for what i am going to do. And i also wanted to say thank you to everybody that is helping me out, it is a big help
In that case, go ahead and get working! Good luck and holler back if you need anymore help. I plan on spending the time to try and make a true equal length ram-horn for my next manifold.
you will need 1 1\2" inside diamater i am currently building one to. but the first one i am going to make is made from mild 3\8 thick steal plate. but my dad can get me a piece of stainless 3\8- 1\2 for my next project manifold. luckily i have stainless wire for our mig welder at work. i hope your project turns out good mine is starting out ok i have the flange cut and grinded down, but i am starting to think that the piece of metal that i am using is to soft and might warp. keep me posted and i will update on my project turbo manny
That 3/8" mild will be very tough to work with without it warping. My 1/2" stainless even warped some just from the welding heat. I’ve never used stainless wire in a MIG before, post some pics on how the welds turn out. I’d just try to keep the heat high and the wire feed on the slow side to make sure it’s penetrating. Those elbows are relatively thick, and you definitely want to make sure it penetrates well into the flange.
If you need a stainless steel plate for flanges, let me know I am selling my left over…about 12x6x.5