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Old 11-26-2008, 02:45 AM   #14 (permalink)
Christ
Moderate your Moderation.
 
Join Date: Nov 2008
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Herbie - '86 Golf Diesel
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Problem with pre-heating the cat - Engines run slightly richer during warm up as a means to heat the cat quickly. A cold cat can handle the excess fuel without gross pollution.

Pre-warmed cat + cold engine == engine still running rich and cat over heating.

At least I think. I have no proof to back this up, other than what I know about excess fuel entering the catalyst, and causing it to heat up substantially.
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