Managing EGR for MPG

[rh77]

Originally Posted by MetroMPG

Not sure if you're saying this, Rick, but EGR isn't lean burn.

With EGR, the air/fuel mixture would remain at stoich (in closed loop via the O2 sensor). It's just that with EGR active, there's less o2 in the intake charge as a proportion of total air mass, so less fuel is introduced. Then, yes, less power, and a wider throttle to compensate, with reduced pumping losses (theoretically).

Darin, I'm trying to wrap my brain around this after a long day, and probably can't offer much but uneducated inquiries -- I figured that Stoich is always the goal of the emissions system (unless in open loop) so the term "Lean Burn" should be described as a Leaner Fuel Mixture when adding an abnormally larger EG recirc. This could result in higher IATs, in leaner mixes, the higher risk of detonation, and consequently higher temps within the combustion chamber. When the ECU finds out that the lean situation is occuring does it not dump more fuel in the charge to cool things down? So in some cases the oxygen and knock sensors report to the ECU to change timing, etc. So multiple factors have to be executed to get this complicated system in good working order for optimum FE. Simply, the whole ECU would need to be replaced or reprogrammed to handle the variables. BTW, does it vary where the EG is entered into the system among vehicles -- I assume directly into the intake manifold in most/all cases?

RH77