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I read through this thread but did not delve into all the links. EGR in my understanding reduces peak combustion chamber temperatures, to avoid pre ignition, and allow more timing advance and higher compression, without exceeding NOX emission standards.
Adding EGR will decrease peak combustion chamber temperatures, which will directly affect the power produced.
Most EGR systems are designed to allow EGR introduction when manifold vacuum is low to non existent. They work with a combination of ported and manifold vacuum working against each other. Modern systems use computer controls to accomplish basically the same thing.
Peak combustion chamber temps only occur when timing is close to max and effective compression is also close to max. This is when NOX levels really jump.
EGR's purpose is to reduce peak temperatures from 3500 to about 3200 degrees. This is one of the main reasons why engine performance has increased so much since the first anemic emission choked engines of the early 1970s.
Think of it this way. If you eliminate EGR you would have to retard ignition timing or reduce engine compression to prevent pre ignition.
In my opinion adding significantly more EGR under conditions other than very low manifold vacuum and very advanced timing will reduce peak combustion chamber temperatures when high temperatures are necessary for best power for fuel consumed.
You may find a better balance, with a slight increase in efficiency, by tweaking the factory systems, but it will probably be insignificant. There may be a balance point that is more economical, but it would have to be where the factory specs were more performance based.
As always these are just my opinions, take them with that in mind.
regards
Mech
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