Just wondering why there aren't any aluminum alloys used in exhaust. I understand that heat would be a factor close to the engine, but what about say, a catback or true dual system, from the headers or even just the y-pipe back?

 

It's a heat issue. Aluminum has a melting point of 1220* F and it's a fairly easy to warp. You would have a hell of a time keeping it from getting exhaust leaks and if you ever had a cat go bad you might even build up enough heat to melt it...

 

How about for a cat free exhaust, and say after the y pipe back or even just true duals? The exhaust heat should be lower at the back of the exhaust, right? I just figured a true dual or even catback could be made and shed some weight vs steel.

 

Even for a catback, when compared to steel it would still be more brittle if it is cast tubing and easier to bend if rolled. Not to mention the greater cost and aluminum does oxidize.

 

If you're that into weight savings, you'd be better off running open headers or just dumping true duals before the axle...

 

Just wondering, I figured it would be a good way to keep weight down, guess other alternatives would have to be looked at.

 

Are you planning on clamping the entire exhaust system to piece it together? Welding aluminum isn't as easy as welding steel.

 

I was thinking of a clamped aluminum catback or duals over the axle. That way duals could be done without the extra weight.

 

It all comes down to how thin you can make the aluminum pipe. Then compare it to a very thin (e.g. - 16ga) S/S pipe. The weight advantage might not be as great as you assume. If you live in the snow belt, the aluminum isn't going to stand up very well to road salt.

As an example, a 6-ft length of 2.5" diam. 16ga S/S tubing weighs about 10.8#. A similar length of the same diameter, but 0.125" wall thickness aluminum pipe will weigh about 7.0#.