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Old 12-24-2021, 10:54 AM   #29 (permalink)
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Merc - '97 Mercedes V230 TD Fashion
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Originally Posted by Autobahnschleicher View Post
The EGR is *not* lowering the EGTs as long as the engine isn't running rich.
Even cooled EGR is hot compared to ambient air/charge air after the intercooler.
The point of EGR in diesels is to get closer to stochiometric ratio to reduce the amount of oxygen that can react with nitrogen, reducing the amount of NOx produced.
However that's a tradeoff with particle emissions as these increase when you run less lean.
I'm not an EGR expert but Wikipedia ("Exhaust gas recirculation") appears to disagree with your first and third statements. Yes, the recirculated gas is hotter than intake air, but it is lowering cylinder temps by reducing available oxygen, and the reduced cylinder temp is the mechanism of reduced NOx emissions. If you can show me a good source to refute this I will happily update the wiki page.
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