Tweaked Perspective
 

this may be a bit of a free-for-all thread, but anything that encourages intelligent discussion is a good thing. :)

so, i was thinking about EGR for some reason, had the realization that EGR is quite literally vacuuming out your exhaust, with the engine being the obvious source of vacuum. of course, this is in addition to EGR being used to reduce pumping losses and lower NoX levels.

obviously, this also only applies to engines that operate with a vacuum, so diesels and certain gasoline engines this doesn't apply to.

anyways, the point is that it's reducing backpressure by "venting" a small amount of the exhaust into the intake manifold, so there is probably a small volumetric efficiency increase due to this.



anyone else have any realizations that were kind of obvious but never quite presented themselves? or anybody have anything to counter this theory?

Guess not. :(

When I was a little kid I thought all liquids contained water.

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. :)