[C3H8]

what does running shell rotella diesel fuel additive, which is a diesel additive, not actual diesel fuel, have to do with me running actual diesel? not much. you are trying to compare a diesel fuel additive, to actual diesel fuel. thats an apples and oranges comparison. they are 2 different things. i dont know how a diesel fuel additive effects youre engine but i do know that i can get away with 15% diesel in my engine without pinging or any effect on fuel economy. i simply run a bit of diesel because its about 60 cents cheaper per gallon at the place i get it. it doesnt really help economy any, but it doesnt hurt either.

egr is an easy system to bypass without the computer knowing. i simply measured the resistance of the egr solenoid when in cruise with the egr valve open, (which was about 40 ohms btw) and duplicated that with a resistor soldered in place of said solenoid. this allowed me to remove the egr system and not have any check engine light or retarded ignition timing. and yes i did check ign timing before and after with a scan tool. running without egr resulted in increased ign timing because as you said, the throttle will be closed more. computer reads the throttle as being a few degrees extra closed (compared to egr on) and advances the timing a bit. (again compared to egr on)

i dont even believe there is ANY pumping losses with egr disabled and removed. yes it is true that egr increases the throttle opening. but did you stop to think why it does that? it's because the egr dilutes the incoming air with inert used up air that has no combustive value. the egr air simply takes up space in the intake manifold and combustion chamber that would normally have been filled with fresh clean air. in other words, you need X amount of air and X amount of fuel to maintain X amount of speed. with egr on or off you are still using the same amount of air and fuel to go the same speed. the only difference is that some of the air is diluted and the throttle is held open a bit more resulting in less timing. this doesnt magically reduce the combustion chamber volume. it simply renders some of the air that is mixed in, un combustable. and as such it lowers combustion chamber temps. lower cc temps? that doesn't sound good for FE to me. and it isnt. so yes with egr working the throttle is held open more, but you are getting less clean air. the 2 cancel each other out. in the end the same amount of clean air enters the engine, with egr on or off, it doesnt matter. only difference is, ignition timing is being retarded a bit with egr on from the throttle being held open.

i get better mileage with the egr removed and my resistor in place, then with the egr properly functioning. and i havent had a check engine light in a few thousand miles that was egr related. and my scan gauge does show increased ign timing during the same drive with i have egr disabled. and my mpg display shows increased mpg's.
i would hazard a guess that egr is nothing more then an emissions control device. it actually increases fuel consumption on my engine. not a good thing for an ecomodder.


keep in mind also that i don't have a little metro engine. maybe things work differently on small vs larger engines.