Stainless or steel exhaust system

[renegade6]

I've been doing some reading and I've seen comments with people having problems with stainless exhaust systems having welds cracking, too much expansion, etc. Is it worth it for stainless or just use steel and have it coated?

[SShep71]

Stainless will expand more than carbon steel, its not uncommon for stainless to expand 1/4"+ over the length of a car. Most of the broken welds I have ever seen in stainless are in poorly designed and fabricated systems, or polished setups where the welds are ground clean and even. Stainless is not forgiving like carbon steel, its the smallest details that lead to problems. A common failure I have seen and dealt with is trying to piece together a system with different grades of stainless (303, 304, 304L ,316, 416,etc) and making it rigid where expansion is constricted to the fastening devices. The different grades of stainless have different expansion coefficients which can cause problems. If you properly designed your system, picked out the proper materials, and properly welded any joints you will have a system that lasts years.

Carbon steel is very forgiving and can be coated, but if you coat it and need to make a change later (cut, grind, modify,etc) you will have problems with the coating. One thing to consider is to do a exhaust setup that incorporated both coated carbon, and stainless. One HUGE drawback of stainless is the cost. Raw material is expensive and because of the problems with working (rolling, bending, forming) it is a struggle to work with. You should always seek advise from experienced fabricators before you start to do any purchasing. This is just my .02 so take it for what its worth.

[Schwartz Performance]

We do stainless pretty much exclusively. If you have steel coated, it'll last a long time- but it all depends on where the car is stored (in a grassy swamp area vs a heated garage) and if it'll ever see salty roads. If you simply can't afford stainless and aren't that great at tig welding, and don't want to learn, I'd go with steel.

-Dale

[parsonsj]

I'm with Dale. I only use stainless, and have built my tool inventory around what's need to do that right. Bandsaw, belt sander, TIG welder, etc.

SS (depending on alloy) has a coefficient of thermal expansion that is less than steel (410) to 30% more (304). 1/4" is about the right amount for total movement based on temps of 1200* at the exhaust flange, 800 at the collector, 400 at axle, and 200 at the tailpipe.

[renegade6]

Gentlemen;

Thanks for the information. What grade should I use and do you all have recommended sources?

[Schwartz Performance]

Stainless works. Were a dealer.... ;)
But really they have great prices. Grade 304 is the most common. 409 will discolor a lot quicker but is cheaper.

-Dale

[renegade6]

I think I'm just going to have to set up a pay allotment to you.

[SShep71]

If you can get it 304L is better than 304. The composition of 304L helps resist a little PITA called IGSCC (Inter-granular Stress Corrosion Cracking). Its kinda on the advanced side of stainless fabrication, however it should be considered if possible. You may be better if you just took it to somone like Dale, and had them do it. You can save some cash if you do it yourself, but doing it twice or having it not turn out right is more expensive in time lost and material wasted. If your fab/TIG skills arent up to it better to not even try.

[Schwartz Performance]

I think I'm just going to have to set up a pay allotment to you.
Hey whatever works... You'll always be a customer ;)

-Dale

[Rich@StainlessWorks]

Stainless works. Were a dealer.... ;)
But really they have great prices. Grade 304 is the most common. 409 will discolor a lot quicker but is cheaper.

-Dale


Thanks for the kind words Dale!

[Schwartz Performance]

Anytime!

Just realized I mentioned 316 is cheaper grade and will corrode easier than 304- oops! I meant to say 409. Too many numbers.
I edited my original post- hope nobody gets confused :)

[alphaenvirmgt]

Mild steel with quality ceramic coating is a great solution.