Hi, I was wondering how the tubular manifolds hold up with the heat our engine's roduce? I am asking because I am thinking about making a manifold for my car. What thickness of tubing is good? Where can I get the flange from the stock s4 turbo?

 

i believe sched 40 pipe (.143 wall?) is what you want, not sure about the flange

 

Durability is in the choice of material and quality of the fabrication, more than the thickness of the material. Material thickness effects more the function of the manifold. You need to have enough thickness to have adequate strength at operating temp, but after that you get into a area where the manifold begins to "wick" heat from the exhaust stream, and heat is the main force in the operation of a turbo.

 

schedual sized wall thickness is relative to the inside diameter of of PIPE. schd 40 2" pipe has a differnet wall thickness than schd 40 8" pipe. Piping measures the inside diameter.

Tubing measures the out side diameter. Tubing also uses measured wall thickness in it's dimensioning.

2" 16ga (.063) 304 S.S. or 321 S.S. is the typical tubing used in manifolds.

 

The flange you can make, if you are going to build a manifold I assume you can make a flange. Lay your stock one down, trace get the required thickness of your metal. Cut, grind, drill and sand the edges if you are perfectionist.

 

.065 is too thin, it heats up too fast and isnt really structurally sound. The big secret is 2" schedule 10. it has a wall thickness of about .120 which is more than thick enough, and you can get 304ss bends from mcmaster for about 8 bucks each. These are cast bends that are already chamfered for welding.... remember to weld with 308 or 316 filler (always use at least 1 grade higher stainless than the base metal)

as for a flange I have mine cut on a waterjet out of 304 plate, but your best bet would be to get them from racingbeat or mazdatrix for the engine side. Doing this for the stock turbo would be a total waste of time since a manifold is one of the more expensive items in a turbo upgrade. Just get a T4 flange and buy a real turbo...

 

I run 16g exhaust pipe and would NEVER build a manifold out of that thickness its far far to thin

I was unaware that schedual wall sizes were measured that way, that was just what i was told to buy (sched 40 1.5" id for my wastegate, and same but 2ish for runners iirc)

 

.065 is plenty good if you are using stainless.
Find a better welder.
Of course thicker is better though.

Crackhead, btw, 16 gauge is .065