The whole EGR "business"

This article explains it better than I could.

Wikipedia EGR

The basic idea is that the less excess oxygen in the power stroke, the less nitrous oxide emissions. I think. So it isn't about re-burning some of the exhaust, it's about keeping the excess oxygen from forming oxides of nitrogen (talking strictly about diesels here). All this makes for a less efficient burn, which actually makes more particulate emissions (soot) which is why the '07 emissions trucks have DPFs. As far as the timeline goes, EGR on diesels started with what was supposed to be 2004 emission standards, but as part of a lawsuit between EPA, CARB, and the engine makers, the '04 standards were pushed up to October '02. Everybody but Cat went with EGR, Cat went with a two turbo setup (Acert).

So I probably haven't done anything but put a bunch more questions in your brain, but there you go.

 

To put it simply in a modern electronic engine EGR is used to control the combustion temperature with the fundamental goal to reduce NOx generation.

For EPA2010 emissions using SCR to control NOx the EGR can be significantly reduced, though it still serves a valuable purpose of reducing cylinder (and exhaust) temperatures.

 

In a nutshell, exhaust is re-introduced back into the engine to kill the oxygen that creates unacceptable levels of NOx. This kills power, creates massive amounts of soot and heat, and slowly and systematically kills your engine oil.
The new SCR engines are the way to go. Yeah the surcharge sucks as well as maintaining SCR fluid levels, but all of the engine killing heat, and the power robbing byproducts of EGR are greatly reduced to where we have our powerful and efficient engines back.

 

Unfortunately there is a lot misinformation here. EGR lowers the combustion temperature, which creates soot. The higher heat rejection requirements are because of the EGR cooler, the engine itself is using less of the cooling capacity than its non-EGR equivalent. The modern EGR engines will produce more power and torque than a non-EGR equivalent at the same emissions output.

Obviously I am not talking about the first generation engines, only the most modern.

 

...which raises EGTs due to slower burn.

 

Still wrong. Diesel doesn't "burn" like a gasoline engine, it explodes, hence the distinctive sound and much much higher cylinder head pressures.

The engine will control EGT to make sure it is high enough to continue the reaction in the DPF, but it is not doing that through EGR, but through back-pressure and timing.

What's the last truck you saw with a pyrometer? Modern engines don't need them, most truck manufacturers don't even offer the option anymore.

 

cool driven trucks with the stuff on it just did not know how it worked. i just knew when it stopped. lots of black smoke lol

 

They both "burn", diesel sound comes from accumulated fuel from ignition delay.

Egts are not kept high for DPF, we don't even have DPFs in Europe. Re tarded timing and EGR have same effect, lower combustion temperature and slover combustion and higher EGTs. Higher EGTs are just a negative side effect of this emission crap, no-one wants it. No-one wants backpressure either.

I have never seen a truck with EGT from the factory, European trucks and drivers have never needed them.

 

Then your EGR stuck open. If it stopped working your smoke levels would be lower.