Like it says, If one were going to fab their own manifold, which is best, and why. Thanks, Carl

 

Straight from burnsstainless.com:

304 stainless steel tubing combines excellent physical properties with a remarkable resistance to corrosive agents found in automotive exhaust emissions.
304 tube is the most cost-effective grade of nonmagnetic stainless steel for general applications, but some professional racing teams use the higher heat-resistant properties of aircraft grade 321 stainless steel.
We have considerable experience with stainless header fabrication and will gladly advise our valued customers.

321 stainless steel tubing is one of the most desirable materials for exhaust systems because of its excellent resistance to fatigue and cracking at elevated temperatures.
It is usually the material of choice for high temperature turbo applications, unless extreme requirements indicate the use of Inconel.

 

mmmmm..... inconel is sexy

 

Seems to me like the 321 would be the best. However, availability and price seem to play a role too. I haven't been able to find any of the thicker piping 321. So maybe a Schedule 40 304L manifold would be just as crack-resistant as a thinner walled 321? If so, then I would personally go with the 304 due to lack of funds. However, you could prolly save some weight by going with the thinner 321...

I've haven't read much information on the 316, maybe its somewhere inbetween the two in terms of physical properties and cost?

 

http://www.spiusa.com/Ref001/austenitic.html

Looks like 316 is used in the food processing industry due to it's resistance to corrosion, specifically pitting.
316 has added molybdenum.


-Ted

 

My whole turbo system is built from the leftovers of an ice cream/butter plant renovation, its type 321 and is the most heat resistant of all those 3, 304 is very common, 321 is the second easiest to find... I use 316l filler rod with the 321, works well....304 is really easy to find and its cheap, but it breaks down quickly ,and cracks easily under heat stress, not bad for intercooler pipes though, just remember to back purge and allow for the "growth" of the stainless ( it likes to shear bolts off)...Max

 

347 rod works best with 321.
Also 304 when properly built and turbo braced properly will last quite a while.
I use aluminum for intercooler pipes, much easier to work with then stainless.

It's much better to build a manifold with tubing rather then using plumbing pipe.
Money permitting, I would use 321 16 gauge for best results.
otherwise you could get away with using 16ga 304 (again built right and braced properly!)

 

Of those 321 is considered best. 304 or 316 will work fine though I have manifolds made out of 304 here that a years old and havent had problems with them yet. Just depends on how you put them together.

 

How do you brace the manifold?Or maybe I should rephrase it and say where do you brace a stainless manifold?As constraining a stainless manifold from moving can't be good either considering the expansion rate of stainless is double that of mild steel.I've heard some brace the turbo to engine and others weld braces between the flanges(header exh. port flange to turbo flange).Which is best?

 

You need to support the weight of the turbo.
SO you make a brace that allows some movement to allow the header to move since s/s does expand. You don't brace the manifold, you brace the turbo!.
As for where the brace ties into depends.
If your motor has stock motor mounts you will need to brace the turbo to your engine.
If the motor has solid motor mounts you could brace it to the car.

I use rod ends and chromoly tubing for my braces. Adjust the rod ends to allow some movement and you'll be fine.

 

Don't be mad that there not rotary's.
I'll be making a nice setup for my car this winter and i promise to post pics!

Anyhow here's a few:

 

love that 2Jz manifold!

 

notice how the wastegate runners stretch the length of the turbo exhuast housing.

it is almost as if they want an equaled system

 

Those are HIS manifolds

enzo250 - Those are beautiful manifolds regardless of what car they are for!

 

^^I agree!! Hopefully someday, I'll be skilled enough to make something like that.

 

controlling boost is very important. the honda's as you know will spin the tires the whole way down the track. Limiting boost in the lower gears is very important for traction.
It's also very hard to do on a high hp motor without proper wastegate placement.

It's amazing how much more power was made by going to long tube headers.
The motors could finally breathe again. Forcing 35+psi of boost in a motor also needs to come out somehow.

 

The best is Inconel 625. Better materials are available but you and I can’t afford it. Inconel is over kill. A little difficult to weld. (The puddle looks like it is full of SHT. Like you didn’t clean your material before welding.) Very good for prolonged temps above 1750 degrees F. Yes it has better mechanical attributes but cost per weight savings in my opinion is not worth it. Very kool stuff though. Next is 347SS. I haven’t found anyone that has mandrel bends of this material. Next is 321SS my choice. (Use 347 filler rod) Very good corrosion resistance when exposed to higher temps. A Thermally wrapped exhaust system (For Rotary use) should not be a prob with 18 gauge. Keep an eye on your exhaust temps. Quite a few hours of run time can be expected before any serious deterioration will affect the structural integrity of the manifold. Support braces should be made to support the turbo’s weight. Lastly 304. Very good stuff can be purchased anywhere in STD pipe sizes. Sch 10 will last a very long time Cheap but heavy. SCH 40 is over kill. Yes people will argue but these are my opinions and I am and have always been weight continence.

 

Iconel is useful when you need more mechanical stability, e.g,: an absolute minimum of expansion/contraction. It doesn't move very much with thermal cycling.

I would use whatever 3xx series stainless you happen to have on hand. Just don't go too thin on flanges or sections exposed to constant high temps. The exact alloy is not going to make a lot of difference since the hot exhaust gases don't (or shouldn't) have much oxygen in them to react with the alloy.

Stainless is also relatively poor conductor of heat, which makes it a good choice for exhaust applications. (Similar to cast iron in this respect) Certainly better than plain, low carbon (1018 type) steel.

 

Find some Mar-M material ... just kidding, who wants a manifold worth more then their car?

Good info guys, its good to see a LOt of people that understand how design a optimum manifold. One thing I never seem to see and should be consided in a good designed/engineered turbo manifold is were the turbo flange meets the pipe/tube. I see a lot now using at least 3" section of pipe straight off the motor to avoid turbulance in the actual port which is good and a no brainer, but I also see a lot of people neglecting this same princable near the turbo flange. There should be a 3" straight section that has a gradual taper to the turbo flange as well to minimise turbulance into the turbine as well so it works like it was designed to. (rule of thumb already mentioned by someon els, 1.5 times the ID after a bend to allow the flow to stablise). Im not saying if you skip this and put a bend right at the flange it wont work or make great numbers, but optimumly you'd want a straight section here also. McMaster also sells coned sections of pipe that mate up perfectly to the pipe sections that people are using for their manifolds. If your using the 2" pipe as opposed to the 1.5" as primaries, you'll find that when you sqeeze it into a square (actually rectangle) port shape to mate to the turbine flange that it will have a slighlty larger ID then the port in the flange/turbine entrance. Get the taper/coned section of pipe as well and squish it (heat it with a torch, use a vice to squeeze, or a hammer, or make your own square shaped mantril and force it into the pipe so it makes a square) and cut the top down till the ID matches the ID of the flange port. This also benifits you cause now you have a straight section before the flange and a nice smooth taper into the turbine .

~Mike...............

~Mike..............

 

Awesome information in this thread guys.

 

Dear Sir,

We take the liberty of introducing ourselves as manufacturer and exporter of
Flanges (including Exhaust Flange) – Hose Fittings- CNC Machined Components and are supplying regularly to US, European Countries. Our major clients are Flexible Hoses, Expansion Joint and Bellows Manufacturers

We have well equipped workshop including facility for CNC Machining.

Our main objective is to provide full satisfaction to our customer in terms on quality, timely delivery,

We request you to send us your valued inquiry.

Thanking you


Satnam Singh

 

Dear Sir,

We take the liberty of introducing ourselves as manufacturer and exporter of
Flanges (including Exhaust Flange) – Hose Fittings- CNC Machined Components and are supplying regularly to US, European Countries. Our major clients are Flexible Hoses, Expansion Joint and Bellows Manufacturers

We have well equipped workshop including facility for CNC Machining.

Our main objective is to provide full satisfaction to our customer in terms on quality, timely delivery,

We request you to send us your valued inquiry.

Thanking you


Satnam Singh