Choice of materials for exhaust manifold.
 

I am wondering why you guys are using stainless steel?Mild steel will give you guys better results for longevity and easier for non pros to work with.I personally use mild steel on all log manifolds.

Re: Choice of materials for exhaust manifold.
 

it depends on the budget... :y

Re: Choice of materials for exhaust manifold.
 

sched 10 stainless els on everything.

mild steel isnt any cheaper so why ever use it.

Re: Choice of materials for exhaust manifold.
 

Because to weld stainless properly it should be back gassed.

Stainless expands and contracts much more under heat than mild steel.

Machine tools suffer while cutting stainless steel.

Mild steel manifolds last longer.

Re: Choice of materials for exhaust manifold.
 

but if you havent noticed, noone gets a hardon for mild steel, its not jdm.

im setting up my backpurge tank monday.

remember its gotta be jdm yo, or noone wants it.

Re: Choice of materials for exhaust manifold.
 

Is leaking out the #1 and #4 runners JDM?Building log manifolds also leads to banana shaped head flanges and pulling out of head studs.

Re: Choice of materials for exhaust manifold.
 

maybe for you it does, i have a surfacing tool *if a flange happens to warp, but i havent had to use it yet. my plates that i weld to do th etrick nicely,

and i have triple check every manifold and have never had a leak, crack or anything of that nature.

Re: Choice of materials for exhaust manifold.
 

You will start having problems.The manifold warps after being heat cycled on the car.It will start with a leak when cold and then seal itself up when hot.Eventually it will ---- out the gasket and then it never stops leaking.

If you are questioning what I know,I have been doing this for a while and was once at your level.

Re: Choice of materials for exhaust manifold.
 

Stainless steel retains heat approximately 30% better than mild steel. This makes for faster spool times on turbo manifolds and less engine bay heat for all cars. Stainless steel is overall just much stronger.

Stainless steel doesnt need special gasses. However because it expands much more under heat, it makes it even more crucial for welds to penetrate 100%. Thats pretty easy to take care of though.

The one thing you don't want stainless steel for is in the header flanges.
Because of the expansion, it can pop off the nuts destroying the studs and cause all kinds of nasty stuff.

At the current cost of steel, SS is barely more expensive than mild for our application.
Even if it was more expensive, the performance gains and strength would still be worth it.

Re: Choice of materials for exhaust manifold.
 

So are you trying to say that this makes a difference in a log manifold?Not that it matters because I use sch40 material with is much thicker.

It does not take special gasses to weld stainless,but it does take proper technique to weld with is time consuming and costs money(unless you want brittle welds with big carbon chunks inside your manifold ready to break off and destroy your turbo).

Its the extra expansion and contraction that causes manifold failure.When the log expands and contracts it causes nuts to start to loosen up and causes a host of other problems related to expansion.

Most of these problems are reduced in equal length manifolds because of the load being ------ out over a greater area.