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Old 12-24-2021, 11:19 AM   #30 (permalink)
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Originally Posted by clarknova View Post
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.
I could dig out a german textbook on internal combustion engines, but you'll likely not understand it because it's in german.
Regarding the temperature:
As long as all the fuel combusts, EGR does not lower combustion temperatures in *diesel* engines as the same amount of fuel combustion produces the same amount of heat.
It is different in gasoiline engines as here it dilutes the air/fuel mixture while keeping it stochiometric and thereby reduces combustion temperatures, where as in diesels it replaces intake air and enriches the air/fuel ratio.

In gasoiline engines it also improves efficiency under low load as it reduces pumping losses as the engine doesn't have to work against as much of a vacuum.
Meanwhile in diesel engines the engine doesn't have to work gaianst a vacuum to begin with.
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