ORIGINAL: Gungadin
Matt,
I was just getting ready to order some teflon tubing from Mc Master Carr for my Focus set up. You say it won't hold up. Are you saying 500 Deg. F isn't good enough, or is there some other issue that causes it not to hold up ?[
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Dan,
Teflon PTFE has a continuous service temp rating of 550F. It will work fine if you use the material directly over the pipe stem and header. But if you use it inside a silicone coupler for example as a spacer, then gasoline exhaust and exhaust from 4 strokes is hot enough to damage it. You see, the silicone will act as insulator and keep the material from getting cooled enough.
Frankly when I melted the PTFE in my set up it actually surprised me since I didn't expect exhaust temp from the 4 stroke to be hotter than 550. But it is. Exhaust temp from gasoline engine is also hotter than 550F. Teflon PTFE will "melt" at around 625F. It doesn't melt in the conventional plastic sense. It doesn't get runny, it just gets soft and gummy and easily conformable. It also expands about 20%, so if it's retained inside silicone rubber, the expanded shape has no place to go so it buckles, blocking off the exhaust port
Matt