Could someone give me the run down on swain coatings please?

Reason I ask is I'm having an exhaust header made for one of my cars, and one of the people I spoke with said I should have it made in mild steel rather than stainless steel

His reasoning was that stainless steel has half the heat transfer rate of mild steel, meaning the exhaust gases in a stainless steel would remain hotter, and since the hotter gases would be less dense theyll take up more volume and will take longer to exit the exhaust system

He told me if you use a mild steel exhaust the heat transfer rate will be higher, meaning the gases would be cooler and therefore denser, so whilst they'd be moving slower theyd still exit the exhaust quicker as they'd take up less room

Now, my thinking was that you would actually want the gases to remain hot
A hotter gas would have more energy/speed and so exit the system faster

This then got me thinking about the swain coatings

I'm guessing the exhaust coatings are used to keep the heat/energy in the system......but then, why do they treat intercoolers?

Wouldn't you want an intercooler to give-up its temperature to the intake gases stay cool?

Questions....

What are the benefits of mild steel vs stainless steel exhausts with regards to the information above?

How do swain coatings work?


As you can tell, I am an idiot and I know nothing

 

On all my turbo builds, I always use 321ss and in tight area's where there is a chance of melting something or fire, I use coatings and or shielding. The coatings work pretty good as tested. As far as keeping the heat/energy in the exhaust gas, that is a very good thing.

I got away from Swain and Jet Hot brands because I have a great powder coat guy near me and I use Cerakote http://www.cerakotehightemp.com/ They make a great high temp coating that works great.

I have also used their piston coatings and bearing coatings with great success.

 

HI,,If you are doing normal steel , not SS , Its a win win to coat the inside and outside of any headers..
Our stock exhaust manifolds retain heat very well because of design and SS dual walled..

 

The thing I don't understand is, why would this exhaust guy tell me mild is the way to go, and that you want the gases to cool down, not retain their heat?

 

Its easier to build a mild steel header that wont crack then with ss but that doesnt doesnt mean its better. Heat maintained in the exhaust preturbo is a good thing.

 

Maybe he is mis informed? Mild steel is cheap and easy to work with so, maybe that is why he likes it? I would never build a turbo header or outlet out of mild steel.

I wouldn't feel comfortable about coating the inside of any pipe prior to the turbo. Should it come loose, it gets thrown into your turbine wheel!

 

If it makes any difference, the header is going on an old naturally aspirated car

The guy says I should have a mild steel exhaust not a stainless one

He said stainless can crack, and that it holds too much heat

He said a mild steel system will transfer more heat, and that that is want a good system should do

He also reinforces the header flanges with brazing

 

Ok, big difference. Mild steel is fine for n/a but, it will rust so, perhaps coat it if you want it to look nice and not rust out.

Personally, I would still do a SS header and just put in some expansion bellows to help with the natural movement of SS.

 

Swain is a company - they offer myriad coatings. Their exhaust coating is completely different from their intercooler coating, for example.

 

My initial thinking was to buy an off the shelf stainless one
But the problem with them is poor design and fitment

This guy makes very nice systems, but only does them in mild steel as he says they give better results

The thing is, my friend has one of his exhausts, and noticed a 30hp increased on the dyno when compared to his old stainless system

Not sure if it's the design or the materials, but this mild steel system gives much more power

Maybe I should coat the mild steel system
Maybe I should buy it and have it copied in stainless

Why would this guy say mild is better than stainless?
He maintains that an exhaust system should allow the gases to cool as quickly as possible

I don't think his logic is right - but the performance improvements from his systems are very well documented

Hmmmmm

 

You have a point there about coating the inside of a turbo header..
I went thru that with coating the turbos IPD plenum's inside also...Calico didnt want to..But Swain said no problem?..I only went with outside coating from Calico because of the quicker turn around time..
I guess it all depends on the coaters advice with his product?

 

Some people can only achieve the temp rating by coating inside and out. My guy will do both but, only coat the inside if it is new and very short tube design so, he can make sure it was applied properly. His inside coating is a "pour in", bake in an oven product. It looked very nice but, I would only do it after the turbo.

To the OP, I'm not sure why your guy is requesting Mild tubing. As long as the design is good and he has good merge collectors, I can't see a big if any performance gain (if any) between the two metals.

Personally, I would split hairs on a few hp and go with whatever will last the longest in your enviroment.

 

SS does crack easier than mild steel, but is the superior material to use. That said many of the headers on the market are mild steel and coated. MS will stand up just fine to n/a exhaust temps. Go MS with a good coating and you should be happy for years.

On a turbo it is completely different. Evil 996tt is exactly correct, 321SS is the material that should be used for tubular exhaust manifolds. It has some titanium in it which helps to stabilize the material at higher temps, providing greater strength, less fatigue and less cracking. There are some even better materials available, but most are very hard to work with (such as inconel). There are also a few trade secrets to help prevent cracking in exhaust manifolds, but few put the extra work in or are not aware of them.