Quote:
Originally Posted by Def
Aluminum will have a lighter density, and you can use more material to get a stiffer structure. Strength depends on many factors, but generally Ti will be stronger.
That said, aluminum works fine for a catback exhaust. Melting point for aluminum is in the 1050-1100 deg F range, and it loses significant mechanical strength around 700-800 deg F. So while the exhaust temps might be around the melting temp, aluminum will have a much higher rate of thermal conductivity than any other exhaust material so it will shed more heat to the ambient air and more of it will stay cooler. Lower material temps mean better mechanical properties.
The short of it, aluminum has been shown to work just fine for an exhaust at least a few feet away from the exhaust ports on tons of cars.
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Aluminum has a melting point between 1050 to 1150 degrees Fahrenheit, yet it gets soft and unstable at far lower temps. here is somthing interesting that i found.
ANSI B31.1 (Power Piping Code, 1980 Edition) neither lists allowable stresses for aluminum for temperatures in excess of 400°F nor permits its use at such temperatures. While it's true that exhaust plumbing isn't power piping, it's still a reasonable guideline to follow, and material that's only good to 3000 psi at 400°F will be utterly worthless at 1000°F.
The end near the muffler would corrode do to the combustion gases combined with moisture form Hydrochloric, Sulfuric, Nitric, Carbonic and other acids. That's why the back end of normal carbon steel systems rust out and the real reason stainless steel systems originally started (not the bling factor!)
the bottom line is yes, you can make an exhaust out of aluminum. no, it wont last long. yes, it will be light. yes, you will have to replace it offten.
thanks.
Mike