PorKen

Is it cost? Difficulty welding/forming? Loses heat too rapidly? Erosion/burning? Expansion/cracking?

I can't think of a good reason not too have an aluminum exhaust system, besides cost or welding issues.

After the exhaust goes through cast iron manifolds/steel headers, there shouldn't be a heat problem?

ErnestSw

Wouldn't uncoated aluminum oxidize to powder very quickly with the heat cycling?

heinrich

Ken if you look at early test pics, you see the entire system glowing ... i suppose it may be ok, and certainly weight-saving in production implementations. Certainly shouldn't corrode as easily as others.

http://www.yamaha-motor.com/sport/ac.../0/detail.aspx
http://www.muzzys.com/160605-99/

jpitman2

Why stop there? We use carbon fibre tuned pipes in Model aero engines.....that would really save some weight!
http://www.bolly.com.au/book/Book.js...er=7&Section=2
jp 83 Euro S AT 49k.

slate blue

Well this could be the reason.

FlyingDog

I've seen carbon fiber BMW exhausts. Titanium seems to be becoming more popular for exhausts.

PorKen

I still don't see a reason not to use it.

Googling, I see many mufflers, some manifolds, and water jacketed aluminum marine manifolds.

I haven't found any full aluminum car exhausts yet.
...

Greg,

Heat may be a problem with alumin(i)um. Not to the structure of the exhaust, but radiating to the car body, or wires, etc.

SharkSkin

Water-jacketed manifold, sure. It never gets very hot. But aluminum tends to begin weakening at relatively low temperatures, ~250°C. In the pic above, the downpipe adjacent to the manifold looks to be over 1200°C if it's steel. It's still 1000°C going into the muffler. If it's Titanium, then it's even hotter than that. I doubt you'll find any aluminum exhaust parts forward of the muffler that are going to last, even in street use.

If you want to save weight, run a straight pipe!

EB338

The aluminum would have to be so thinck to withstand the heat that it wouldnt end up too much lighter than the thin wall steel, not to mention bulky.......

cobalt

Temperature way to hot. Thickness doesn't matter. Exhaust temperatures are at or exceed Aluminum's liquidous temperature. Most cast aluminum is poured around 1300-1400 degrees F. At 1200 degrees you would have a hell of a mess to clean up.

Fabio421

The heads on our cars are aluminum. The exhaust gasses should be at their hottest right at the exhaust port of the head. The heads don't degrade because of it.

EB338

The heads are liquid cooled, and they are a much thicker piece of aluminum

PorKen

The heads are water cooled though. I have not seen them, but I understand that euro engines with air injection after the exhaust valve have stainless steel inserts, to combat, I assume, heat from residual gas being burnt.

Would a water jacketed complete exhaust system make any sense? If coolant were pumped front to back, it would even out the temperature of the exhaust, and keep the gas speed high?

Would water would make a resonance free muffler?

I've been wrestling with the idea of making a one-piece exhaust system (no cat), with valved sections that would keep the gas speed constant, and be very quiet.

EB338

a water cooling jacket would add weight to say the least and thus totally defeat the whole point wouldnt it?

PorKen

I think only the manifold and front pipes would be a problem. The front muffler, maybe.

Past the front muffler or cats, the exhaust temperature plummets, and I think aluminum would be doable.

I was more postulating using water for rear warming, and sound deadening, as part of a complete system. With thinner water cooled aluminum pipes, the system should not be too heavy.