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Motor Vehicle Maintenance & Repair

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  • In the first paragraph, do you mean the catalytic converter needs to run inside it's thermal operating range? Commented Jan 26, 2016 at 20:11
  • Actually it's a chemical range as it turns out. The heat is a by product of having the right air / fuel ratio, but the correct ratio is what lets the catalytic work correctly. I believe @Zaid is posting something soon that explains it better than I am here. Commented Jan 26, 2016 at 20:16
  • So in a sense I was correct as it needs to be inside its ideal thermal range as well otherwise as you said the increased temperature will have a knock-on effect? Commented Jan 26, 2016 at 20:27
  • Well, I'm not sure I'm following you. What I'm trying to say, and apparently not well, sorry about that, is that the air fuel ratio being off causes there to be a thermal side effect. But it's the chemical a/f ratio that must be right for the cat to work. Commented Jan 26, 2016 at 20:43
  • The leaner the mixture the more oxygen it has. More oxygen means more 'rapid oxidation' which means more heat. Commented Jan 26, 2016 at 21:52