Homemade manifold

[dft24ds]

My question is simple has anyone ever made there own manifold at home with a pipe bender, tubing and a welding machine?

If so how did it work? Any problems that you ran into?

The reason why I ask is because I've been looking at a coulple of manifolds and it doesn't seem all that hard to do beside lining everything up right and getting it all to fit.

[eddiec]

unless you already have a bender, using prebent mandrel bends may be more effective. beyond that its seems like a pretty str8t 4ward fab job.

some company offers a kit to make your own log style manifold with weld els.

[4felix20]

http://www.jgstools.com/turbo/thk1.html

here's some kits, if that's what you're looking for...

[dft24ds]

Yeah I've seen those but what I was really asking is if anyone has ever made there own equal length mani?

[Chezedik]

Most people do not have that kind of equipment at their disposal.

[fiznat]

There are some people who have done it. It takes a lot of skill and quite a bit of design work to get everything to work together perfectly. I'd really like to try to do it one of these days, ...once I learn to weld better and have the time to sit down and plan something out.

Do you have the means to do something like that? It would be really cool to see a nice homemade equal length mani come together.

[dft24ds]

Actually I have a whole metal shop to my disposal at the hobby shop on base here, or should I say one of the two bases here. They are about 20min. from each other. I already know how to weld and have fabricated quite a few things in my time so I'm almost certain I can do it by looking at some mani's and getting ideas

[95 kat]

I have a jgs kit that has elbows and straight pipe. It has a flange too. I can weld pretty good being i am into minitrucks also and have built a few cab back frame sections and am rebuilding my whole frame for my s-10. I am going to weld up my kit myself. If you want if I can borow my girfriends camera I wil try to take a few pics when i get done.

[WDRacing]

If you can weld and have the pipe, then its easy...if you can weld and the metals tech guys are going to let you use their shop, hook it up.

Are you using the base hobby shop or the actual sheet metal/machine shop??

[dft24ds]

Actually I'll be using both the hobby shop and a blacksmith's shop that I used to work for in Baton Rogue (I go there quite often)

Hey 95 kat can you take some pics when you finish I'd love to see the final product

[gomdevil]

What about using the lost wax method and casting a manifold?

You build a model of your manifold (with pour veins) out of casting wax using cardboard tubing for support.

Then setup a plaster mold container, place wax model in it and pour plaster.

Then burn off the wax, melt a quality casting iron recipe and pour.

Then bust off the plaster, and grind the imperfections out of your manifold.

Anyone think that would work better? It would certainly be cheap as hell to do.

[toki]

you realize 4 curly pipes in to a collector =/= equal length..right? Hope you're pretty good with CAD if you really want an equal length manifold. Unless you're shooting for upwards of 400whp, there is little reason for an equal length over a log.

[Skidmark]

I second the log suggestion. I made mine in a couple of hours and that includes welding the log to the wrong side of the head flange, cutting it apart with a bandsaw, and reattaching it to the other side, lol. Equal length headers of the proper proportions requires a lot of complicated stuff that I don't know crap about. And I wasn't about to learn it all, THEN sit down and design and fab the header just to gain a few more peak HP & RPM's of spool time. Not to mention it only cost me $100 If you are really determined then more power to you, but I think after many hours of scribbling, cussing, and scratching your head, you'll be chomping at the bit to just buy one. It was a hard lesson learned for me, but one day I realized that some DIY projects are a huge waste of time. If I put in all the hours it took me to make that crap, I could have just been working extra hours at my day job, and I would have been able to buy professionally made stuff with money to spare, LOL. If you do chose to do it, good luck, you'll need it, hehe.

[95 kat]

yeah man i will take pics. I have to get the motor together first and set in the car. I just got most of the block together tonight. I will send you some when i get it done.

[A34D4ME]

Get the JGS kit for $100 + change.

I'd be willing to bet that equal length stuff is mostly BS. Reason being that the pressure will be equal everwhere in the manifold.

I think people conflate the mechanics of equal length exhaust manifolds with equal length intakes which have a completely different dynamic. In an intake things are much more sensative.

It's possible there might be some small difference but I'm sure you'll never notice.

[dft24ds]

I realize that it will take more work but itsn't that the fun in it? Doing something not everyone is capable of? I must say as tempted as I am to bend all the pipes myself and fab. everything up, I believe it will be alot easier to buy pre bent pipes and just weld them up. I'm trying to "emmulate" the groundzero mani if you look at it you can count 12 90 degree elbows two 45 and some straight peices to fill in the gaps.

Ok so I know in a perfect world I would order these peices and weld it up and be done but we don't live in a perfect world so I know there is going to be complications and problems along the way....but thats the fun in doing it yourself. So I'm think I'm ready for the headache and trouble of it I find myself quite creative when it comes to stuff like this so I think I can pull it off......the hardest part will be persuading my wife why I "need" a turbo LOL any suggestions on that?

[jmhalder]

its not that "equal length" is BS, its just too damn expensive for most of us, i am personally going the JGS log mani route

[WDRacing]

Look at the fastest turbo cars ever built on the planet. The Buick Grand National. Thye used the a design that most people would laugh at. Two log manifolds, the one on the drivers side has an outlet pipe that came under the motor and attached directly to the back of the passenger side log. Which has a flange on the front side for the turbo. Most GN guys don't even think about a mani swap until they hit the 650whp mark.

[Titan]

I'd be willing to bet that equal length stuff is mostly BS. Reason being that the pressure will be equal everwhere in the manifold.

Wrong. You are confusing static pressure with dynamic pressure.

Because of this, you have to take flow characteristics into account.

You can see this by doing a fluid dynamics comparison of the two, where you will see the equal-length manifold vastly outflows a log.

However, I personally believe you do not need an equal length design to improve the flow characteristics dramatically. I think a tubular manifold would do just fine, regardless if the runners are slightly different length.

Look at the fastest turbo cars ever built on the planet. The Buick Grand National. Thye used the a design that most people would laugh at. Two log manifolds, the one on the drivers side has an outlet pipe that came under the motor and attached directly to the back of the passenger side log. Which has a flange on the front side for the turbo. Most GN guys don't even think about a mani swap until they hit the 650whp mark.

Simply because GN's make great power on log manifolds does not mean there is no room for improvement. Sure they work, but they are hardly the ideal solution.

Examine a formula 1 turbo manifold from the turbo era of the late 70's/early 80's. These machines produced 1500hp on 1.5 liters!!I guarantee you these manifolds did not resemble a log.

I realize this is an exotic example, but it gives an indication to what the pinnacle of motor sports considers to be a proper manifold.

Renault RE20



And just on wow factor, the charge pipe setup:




Modified by Titan at 4:38 PM 12/27/2005

[Titan]

On a more realistic note, here is a comparison between a log manifold and an equal length Full-Race manifold on an SR. This test was done by Enthalpy and Matt-Back.

Exact same setup, test was performed by swapping manifold on the exact same motor.



Log: 300.14 rwhp 231.72 rwtq

Full-Race: 360.12 rwhp 266.79 rwtq

A gain of 60 rwhp and 35 rwtq. Not bad.

[A34D4ME]

That is impressive. Which manifolds were used? Was the "log" type a POS that used restrictive piping or had leaks?

The reason I ask is because any time numbers come up that are that significant, it's usually a sign of error or some overlooked factor.

I highly doubt a well made "log" type such as the JGS tool would lag that far behind if all else was truely equal.

[Titan]

That is impressive. Which manifolds were used? Was the "log" type a POS that used restrictive piping or had leaks?

The reason I ask is because any time numbers come up that are that significant, it's usually a sign of error or some overlooked factor.

I highly doubt a well made "log" type such as the JGS tool would lag that far behind if all else was truely equal.

The log manifold was a JGS tools manifold.

From the post in the link:

We (Myself and Mattback) built a car for a customer that wanted 500whp. Specs are as follows:

CP Pistons 9.0:1 CRStock Rods w/ ARP rod boltsARP HeadstudsGreddy HeadgasketHKS 264 Step 2'sRASGreddy valvespringsGreddy Intake ManifoldGarrett GT3040R TurboROM tune - Z32 MAF, 96# injectorsJGS Tools Log ManifoldHKS Intercooler

It is not so much the nature of the bends in the log manifold that create the restriction. A log manifold by definition is more restrictive then one of tubular nature.

[A34D4ME]

I wonder how a tubular manifold with softer bends but not necessarily equal length would compare?

I bet the major difference is in the tight bends. Still seems hard to believe though - 60HP!

[Iamjohnhayes]

are there any pics of this manifold that they made?also what boost level was done at each run?

[WDRacing]

Titan, I never said that the log was the eend all to tuning, nor did I say that it could not be improved upon. I simply gave an example of a log setup that is of very poor design that works very well.

The equal length vs log mani has another thread on here that is several pages long. If someone would like to dig that up, great, if not, lets just keep this thread on topic...which is building a home made style manifold.

WD

[A34D4ME]

Well, it's hard to overlook those results. After seeing that, I'd defenitly keep my angles below 45 degrees. I'd be willing to bet that is the major factor.

[Iamjohnhayes]

just keep it smooth. you can use 90 degree bends just make sure they are wide and it should be fine

[WDRacing]

The collector is also a MAJOR flow restriction if built wrong.

[A34D4ME]

I bet a lot of it has to do with how the collector flows into the flange. The particular log manifold in question just uses a flat flange welded onto the side of a tube. There has to be a huge lip there that causes all kinds of turbulance with streams of gas running into each other from every angle.

Seems like this type would need to build pressure where the other type could depend on the force of the gas volocity with out so much pressure.

[eddiec]

yes, if i was a exaust gas molecule i would hate having to take a hard 90 turn to get to the turbine. that and slamming into my fellow exhaust gas molecules would suck as well.

so the collector is important for performance. but for cheapness easy to manufactuer the log wins unfortunately.