extractors: stainless or mild steel?

[matrix]

hi all, ive been looking at gifferent extractors (coz i want some) and cant figure out what the performance diferences are between s/steel and mild steel. one exhaust place said that s/steel are not as good because they are a harder steel and dont expand or something? i dont see how this could make a difference as long as the bends are both mandrell done and the internal daimiter is the same.
the reason i want to know is that i can get s/steel lots cheeper than milds but i wont if they are no good.
any thouhgts would be apreciated.

 

[alpinenz]

i have seen alot of people in proformance cars use stainless steel exhaust systems and are rated very well mild steel is there i think as a cheaper option. well thats my thoughts anyway

 

[blofly]

Generally for a street car you don't need stainless steel exhaust systems. The only advantage to stainless is the life span that it has.
You can have a stainless system fitted to your landcruiser, hilux, triton or basically any car that you would use to put your boat in the salt water, off a boat ramp where there is a good chance that salt water will contact the exhaust and possibly cause accelerated oxidation of the system.
But there is an advantage, slight though it may be.
The Catalytic converter in our exhausts has a job to convert the main "problem" exhaust gas (carbon monoxide) into a far less harmful, carbon dioxide and water vapour, as well as producing traces of sulphur dioxide and copper oxides.
There is a disadvantage of this process where the sulphur dioxide mixes with water vapour to produce sulphuric acid. The sulphuric acid has the potential to accelerate corrosion and oxidation in both stainless steel and mild steel exhaust systems, more so in mild steel systems than stainless steel systems.
But that goes for the system after the catalytic converter, before that the exhaust gasses are very hot and do not contain water vapour so the potential for internal oxidation and corrosion are very minimal so the mild steel extractors you ask about would survive at least 7 years of use
But if you use water injection then of course the risk of corrosion and oxidation increase dramatically :my: