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blue2000s · 10-26-2007, 05:11 PM

Water is a byproduct of combustion, in a VERY simplified form,

2HC + 5/2O2 -> H2O + 2CO2

When the exhaust isn't warmed up, the H2O from combustion can become cool enough to condense on the inside walls of the exhaust tubes and muffler. The further down the exhaust you go, the more likely the exhaust will be cooler, and the more likely it is to find water. Ever wonder why mufflers rust out before anything else? This is one of the reasons (not the only one, of course).

In order for the water to completely re-vaporize, the entire exhaust system has to reach at least 212F. This amount of time varies with the engine, the exhaust system, the way it's driven, the conditions outside and a few other things.

There's really no set amount of time that you can say for sure that the muffler's up to temp, but 10 minutes might be on the short side, especially on cold days. You could measure the muffler in an unshielded location to tell if it's reached this point.

Zinc plating (galvanizing) works great initially to protect steel if the surface is well protected and metal forming is done either before plating or is fairly minor. A lot of times, holes are drilled or bends are made after the plating process, exposing the steel to the environment.

But zinc plating wears out eventually, the speed of which is dependent on the environment to which it's exposed. But the more often the exhaust is exposed to moisture, the shorter the amount of time it will be protected by the plating.

10-26-2007, 05:11 PM	#14
blue2000s Porscheectomy Join Date: Mar 2006 Location: Seattle Area Posts: 3,011	Water is a byproduct of combustion, in a VERY simplified form, 2HC + 5/2O2 -> H2O + 2CO2 When the exhaust isn't warmed up, the H2O from combustion can become cool enough to condense on the inside walls of the exhaust tubes and muffler. The further down the exhaust you go, the more likely the exhaust will be cooler, and the more likely it is to find water. Ever wonder why mufflers rust out before anything else? This is one of the reasons (not the only one, of course). In order for the water to completely re-vaporize, the entire exhaust system has to reach at least 212F. This amount of time varies with the engine, the exhaust system, the way it's driven, the conditions outside and a few other things. There's really no set amount of time that you can say for sure that the muffler's up to temp, but 10 minutes might be on the short side, especially on cold days. You could measure the muffler in an unshielded location to tell if it's reached this point. Zinc plating (galvanizing) works great initially to protect steel if the surface is well protected and metal forming is done either before plating or is fairly minor. A lot of times, holes are drilled or bends are made after the plating process, exposing the steel to the environment. But zinc plating wears out eventually, the speed of which is dependent on the environment to which it's exposed. But the more often the exhaust is exposed to moisture, the shorter the amount of time it will be protected by the plating.