Hi,

I've read many posts about EGRs here, and I know it is a controversial topic. But, I was reading the newspaper today and saw this definition of an EGR valve by the Auto Doctor:

"The purpose of the EGR valve is to cool down the internal engine temperature and lower the very harmful NOX coming out the exhaust. Lowering the internal temperature keeps the spark plugs, piston and valves at correct temperature as well. The EGR valve and operation are essential for long-term engine life." (Junior Damato)

Assume that EGRs in diesels and gasoline engines do the same thing, I make the following points:

1. The exhaust coming out of the engine is hotter the intake air. The first things that comes to mind is that it is not possible for the hot exhaust to cool the engine. So why send it back to burn again? It would be like inhaling your own breath.
2. However, hot exhaust theoretically continues no oxygen. Less oxygen in the intake air causes the combustion process to burn cooler.
3. But, more oxygen makes more horsepower in a diesel since the molecules of diesel can more easily find a molecule of oxygen combine with.
4. So, if we disconnect the EGR, we would be causing the engine to operate at a temperature higher than what is was designed for.
5. Or, we get more economy and horsepower without an EGR valve.

What's your opinion?