Just thinking
08-22-2002, 11:24 PM
#1
Racer
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Just thinking
First I was watching the Gumball movie on AMC(maybe TMC) and it made me think:
Why aren't there any aluminum headers and exhausts?
The only answer I can come up with is cost, but it really isn't that much more than stainless.
One other thought I came up with is the Al is a better heat conductor, thus the egt out the tail pipe would be lower. Haven't done anymore analysis thermo and stuff, but like your input.
thanks
Why aren't there any aluminum headers and exhausts?
The only answer I can come up with is cost, but it really isn't that much more than stainless.
One other thought I came up with is the Al is a better heat conductor, thus the egt out the tail pipe would be lower. Haven't done anymore analysis thermo and stuff, but like your input.
thanks
08-22-2002, 11:54 PM
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Perry's got it... plus, aluminum weakens at rather low temps, much lower than ferrous metals, well below what you see near the head ports. Note how much mass & cooling you have around the exhaust ports & cylinder walls... Not sure how well it'd do with the corrosive elements in exhaust gasses. It also handles fatigue cycles poorly (vibration and heating /cooling).
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08-23-2002, 12:58 AM
#4
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Aluminium conducts heat about 5x faster than steel, so you'll end up with a hotter engine bay. Plus exhaust gas temperatures can actually be hot enough to MELT aluminium.
Not that steel is completely impervious to the heat either. Stainless 304 can have carbon-migration issues with the heat from headers (321-SS is better). In fact, the best material for exhaust headers would be titanium. Right in between steel and aluminum in density and conducts heat slower than both of them. Ceramic coat some Ti headers and you can probably touch it with your bare hands at full-throttle!
Not that steel is completely impervious to the heat either. Stainless 304 can have carbon-migration issues with the heat from headers (321-SS is better). In fact, the best material for exhaust headers would be titanium. Right in between steel and aluminum in density and conducts heat slower than both of them. Ceramic coat some Ti headers and you can probably touch it with your bare hands at full-throttle!
08-23-2002, 01:08 AM
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they have a somewhat new method of ceramic coating aluminum. I think this might be the next gen. of headers. Lighter, coated on the outside and inside so they hold the heat well. The coatings they put on aluminum are a powder coat type coating but its ceramic and holds up under high heat. Higher heat than the melting temp of the aluminum. They say it works out great and lets you use aluminum for higher heat applications than you usualy can. Do a search on the net for ceramic coating aluminum and it should come up. There are a few places in the US and some in the UK that do this type of coating now.