06-20-2015, 10:09 PM
The absolute best performance occurs at a slightly richer mixture than 14.7 to 1 but this will result in higher levels of carbon monoxide in the exhaust stream as there will not be enough oxygen atoms to combine with all the carbon and CO readings will be elevated as seen by the 5 gas analyzer.
"immgunn" said it well in his earlier post. As fuel pumps weaken or air leaks occur the O2 sensor reads the amount of oxygen in the exhaust and is constantly trying to alter the fuel ratio to eliminate Hydro Carbons and NOX. This makes the EPA happy but weakens performance but only slightly.
Engineers spend a lot of time creating fuel maps but it is a compromise and their primary objective is to satisfy the EPA. After market tuners are more concerned with performance and want to provide a margin of error as well. Lean conditions are dangerous as they lead to higher combustion temperatures. After market tuners richen up the fuel maps and turn off the O2 sensor as they do not want the ECU to take control and try to achieve the 14.7 to 1 ratio again. This would ruin all the time they spent creating the fuel maps.
If anyone is interested JD Halderman has some great books on drivability and electronics.
"immgunn" said it well in his earlier post. As fuel pumps weaken or air leaks occur the O2 sensor reads the amount of oxygen in the exhaust and is constantly trying to alter the fuel ratio to eliminate Hydro Carbons and NOX. This makes the EPA happy but weakens performance but only slightly.
Engineers spend a lot of time creating fuel maps but it is a compromise and their primary objective is to satisfy the EPA. After market tuners are more concerned with performance and want to provide a margin of error as well. Lean conditions are dangerous as they lead to higher combustion temperatures. After market tuners richen up the fuel maps and turn off the O2 sensor as they do not want the ECU to take control and try to achieve the 14.7 to 1 ratio again. This would ruin all the time they spent creating the fuel maps.
If anyone is interested JD Halderman has some great books on drivability and electronics.