Quote:
Originally Posted by Dave-ROR
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. |
Aluminum is more expensive than mild steel, and is less durable at temperature, that's why they don't use it in street cars.
But what's a reasonable length of time? A street car is run mostly at part load where exhaust temperatures are low. Vibration and other stresses can be dealt with in the mounting system, at least enough to extend the life of the exhaust. Where I'd be rather concerned is a racetrack, where the exhaust temperatures are consistently high enough to melt aluminum. In the future as we see forms of exhaust heat regeneration that reject exhaust at temperatures that look more like 200-300C instead of 800C, then I think aluminum would be competitive against Ti/steel in all respects.