morrisosu

I have yet to find a positive answer on this question, is the commanded equivalence ratio that is present in your CAN based ScanTool an accurate measure of the A/F ration you are getting when using the idea below or is this what the PCM wants to get instead of what you are really getting?


OL EQ RATIO = EQ_RAT: Commanded equivalence ratio is used to determine the commanded air/fuel ratio of die engine. For conventional oxygen sensor vehicles, die scan tool should display 1.0 in closed-loop and the PCM-commanded EQ ratio during open-loop. Wide-range and linear oxygen sensors will display the PCM-commanded EQ ratio in both open-loop and closed-loop. To calculate the actual A/F ratio being commanded, multiply the stoichiometric A/F ratio by the EQ ratio. For example, stoichiometric is a 14.64:1 ratio for gasoline. If the commanded EQ ratio is .95, the commanded A/F is 14.64 × 0.95 = 13.9 A/F.

Sorry if I missed this in a post somewhere I just can't find a ton of info on it.

Thanks!

mazdatech177

the "commanded" value for anything is what the PCM wants to have, it is by no means what you actually are getting. A/F ratio is a constantly changing figure in a fuel injected engine. the engine will run rich for split second then run lean for a split second. its all about the average. these changes wont show up on an aftermarket A/F ratio gauge, but they are there. to verify this just watch a live action view of your upstream 02 sensor (number 11 on an rx8) and at the same time watch your short term fuel trim value (SHRTFT1). they will be an inverse of each other. as your o2 sensor reads rich, your SHRTFT will be in the minus percentage. its a constant cat and mouse game between the two to achieve stoich ratio

morrisosu

Awesome! Thanks for the info!

mazdatech177

you are welcome

love the STNG quote