Quote:
Originally Posted by pgfpro
Thanks for all the great info. I'm going to ponder this for a while. 
What do you think I should do at this point?
I did another run today. At 22:1 A/F I could actually notice a loss of power. So I went back to yesterdays fuel map. It kinda scared me. Something just didn't feel right. But it did get 66.1 mpg today on the old fuel map.
Do you think running more exhaust gas into the engine would help?
quote> Engineering Fundamentals of the Internal Combustion Engine by Willard Pulkrabek "lean mixtures have lower combustion tempertures, caused by the excess nonreacting gases, and this eases the knock problem"
What do they mean by nonreacting gases? |
Spent hydrocarbon gasses. Not having any internal chemical energy available through the spark ignition process or combustion. Nitrogen and Oxygen (NOX). It's inability to do work through this particular process. However still recognized as a gas as their single elements (Gases are considered the lighter element "fuels" ie: CH4 being methane, C3 H8 being propane on up till you get to the C7-9 H8-14 and above being liquid fuels up to thicker Naptha etc. Gas being typically C8H18. Technically speaking "gasoline" is not a gas but should be referred to as a liquid fuel.)
Your EGR valve is what does exactly that. Designed specifically to reduce the NOX emission gasses caused by normal to lean A/R ratios in the combustion processes. (google to read how it does this, there are many engineers who find it counter productive and NOT provide a "complete" burn as suggested) It injects a small amount of exhaust gasses to the intake system or directly to port. Your lean condition, by the way, is creating a very high output of NOX. One of the down sides to the combustion of those A/F ratios. Some try to increase this input but find it WILL limit your ability to run the lean A/F ratios you currently show.
Understand your vehicles engine by design has limitations. Your ECM will not be able to control or keep up past where you are right now. I'm surprised it's running much at all at where you're at with your A/R readings now. A-typical for your type of fuel delivery and management system. You can run into detonation problems due to the fuels characteristics (there still is a surface tension issue even at the mole count that is entering the chamber at this point without further disassociation of the fuel molecules) and duty cycle of the injectors, two quick thoughts to limitations.