I don't know anything about volumetric efficiencies and so forth, but after reading various EGR related posts, I was prompted to check when my Datsun is actually using the EGR system.
I hooked a vacuum gauge into the hose that operates the EGR valve diaphram to see what happens.
It seems to only have vacuum (a stable 20kpa or 1/3 full manifold vacuum) in cruise conditions, nothing at idle or during over run and only after the engine is warmed up.
I'm not making any particular point with this, I just thought others may be interested in checking when their car's EGR is actually working.
