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Scott, you're starting to get a handle on it.

Greg, essentially the analogy with ambient temps and water condensates is not where this issue is. High temperature acid dew points and ambient temp water dew points are miles apart.

If you have the time and for others that have an interest in this subject, please read material in the following links to help you get your head around it. The examples provided are centred around industrial combustion processes and stacks but the fundamental issue of combustion, the formation of acidic gases and the effects of acid dew points on metals is the same as it is for cars.

http://www.hbscc.nl/publications/56%20c ... ingscc.htm
http://www.landinst.com/combustion/prod ... wpoint.htm
http://www.bycosin.se/Deposits_more.htm

Ok, I'll buy that. In your earlier post you said "dewpoint". That's a pretty strictly defined term relating to air's ability to hold water. The term "acid dewpoint" is something else. I agree it's possible that acid dewpoint could be the issue here.

Scott,
Condensation is the result of air being cooled below the dewpoint. If condensation occurs in the exhaust (or anywhere on the car) it's because the car has cooled off and is at or below the current dew point temperature. That can easily happen when the car is parked overnight.

Greg,
just what I was thinking there.

as for what acid.....well...I work in an acid plant. We make nitric acid in particular by burning ammonia on a platnum gauze (think catalitic converter here) which makes oxides of nitrogen (nox). That nox is then bubbled through an absorber tower....water is the initial liquid in the tower and nitric acid is the product that comes out.

Nox is one of several exhaust gasses, but combined with water makes nitric acid....and boy does it rot carbon steel fast!!!!

Scott

Looking back into my chemical compatibility charts, aluminium or 304 stainless will react much the same in sulphuric acid - badly
So the answer here is - keep the exhaust gasses hot near the tail pipe by keeping the throttle WFO - no problem.

Anyone know if how Jarles headers performed? Looked like a great design but I didnt see any posts for the results.
-Tom P.