Quote:
Originally Posted by Isaac Zackary
Yes, NOx increases with temp. But doesn't it increase with more available oxygen too? All I know is that a lot of guys report lower temps at 16:1 AFR and leaner. Please correct me if I'm wrong. Of course there's more to it then just AFRs. There's load and timing too. The guys reporting lower EGR's while running 16.5:1 AFRs are for the most part doing that at part throttle, but enriching it to 13-12.5:1 for full throttle.
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Basically the more excess oxygen going through the engine the less effective the catalyst becomes. So a lower and lower percentage of that NOx produced gets treated.
16:1 is about where the flame temperature is hottest, but combustion temperature and exhaust temperature are very different. Under heavy load the exhaust temperature at slightly lean conditions will be quite high.