Quote Originally Posted by daleulan View Post
That being said, with EGR there is a peak efficiency point where you've lowered NOx as much as you can and advanced the timing as much as you can and if you increase the flow rate any more then you get an efficiency drop - if some is good, more is not necessarily better. Just like tequila. It also should help lower the exhaust temperatures at part-throttle.
IIRC, that threshold is where the amount of exhaust gasses in the chamber make up so much of the air/fuel charge where misfires are inevitable. i would take a guess at saying that a stronger ignition system would allow higher concentrations.