[Dave-ROR]

Originally Posted by serialk11r

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.

You are forgetting about vibration :P

An aluminum exhaust simply won't last any reasonable length of time on a street car.

Perhaps a mix of SS and AL with SS closer to the cat, but that probably has it's own issues.

Let's face it, there's plenty of reasons why manufacturers don't do it, it's not because no one has thought of it before

If you want light, Ti is the answer. It's not cheap though obviously.