EGR

[Wesley]

While I agree that the associated loss from the throttle body is sidestepped, increasing the amount of inert gas also reduces the specific heat ratio of the motor. You do see reduced heat rejection from the lower temperatures, but it seems for every advantage there's a drawback that keeps efficiency around the same.

[bhatia]

EGR increses specific heat of mixture. so rise in temperature are lesser which reduces chances of self ignition. so calibrator may use more advanced ignition timing and improving the efficiency.