Quote:
Originally Posted by MKIV
It is the same reason as alum. con rods. Race cars okay, street no unless you like to change your rods with every oil change.
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I don't think that's a relevant analogy. The exhaust pipe is under very little stress. I don't doubt that an aluminum exhaust would probably start developing stress fractures or something after some time (possibly sooner than most owners would be happy with), certainly before any stainless or titanium exhaust, but since there's little structural integrity required from an exhaust pipe I think it's not fair to compare it to a critical engine component.
I have no idea what exhaust temperatures are typically, but I imagine that after the catalyst there should be enough cooling for the exhaust pipe to let it withstand the heat.