SGKent wrote:Here is a post from our beloved Karl re EGR before he passed on to the Light:
Karl wrote:Not quite what the EGR system does.howiesfamily wrote:EGT stands for Exhaust Gas Recirculation. It is supposed to take any unburned gas from the exhaust and run it back through the engine so that it doesn't get vented out into the air and hopefully give you another mile or two.
EGR was designed to stop the formation of Oxides of Nitrogen, NoX for short. The 3rd bad boy of smog pollution, behind CO and HC.
NoX is formed when the combustion temps exceed 2500 deg F.
The EGR valve lets in spent exhaust into the mixture to lower combustion temps.
On American made cars, the engines are borderline lean to pass smog check. If you cap off the EGR valve, the engine pings and slowly destroys itself. 99% of the old timer mechanics don't have a clue and then they create more problems.
When the bus engine has all it's smog systems working together at 100%, it runs the best it was designed.
It sounds like a working EGR system makes the engine run cooler because the engine is not using as much combustable oxygen as it does without an EGR. Cooler is better right? Plus, there is the benefit of not polluting NoX.