The ignition table has nothing to do with what we're talking about. VE has everything to do with what we are talking about. That's why the fuel map is sometimes referred to as the VE table. The PCM uses the table values to modify the base injector pulse-width based on what point in the table the engine is operating at. The base injector pulse-width is the amount of fuel required to produce a stoich mixture at 100%VE and a certain temperature, given a specific injector flow rate and engine displacement.Low-Speed wrote:you have 2 tables. One for spark, one for fuel. VE doesn't directly factor. The mappings on the fuel table and spark table correlate a MAP and RPM point with a fuel injector pulsewidth. Its a very simple system. The MAP indicates load, at a given RPM.
If you understand what I just wrote, your theory of Chrysler switching injector sizes between model years becomes more plausible. A switch to a different size injector would simply require a modification to the base pulse-width rather than having to modify the entire VE table. I think its worth while to investigate further into it.
In open loop operation, the PCM has no feedback from the O2 sensors. It has no idea what the air/fuel ratio is. Since airflow is calculated based on pre-determined values as I explained earlier, it will not provide enrichment if airflow is increased over what the stock engine normally generates. This is where a piggy-back computer can help control enrichment (as long as the MAP sensor range is not exceeded).The reason 25 percent is the limit regardless of open/closed loop operation, is the factory calibrates for 75% duty as the normal max on the injectors. That leaves margin. from there, it applies a percentage richening based on IAT, etc. But, the table runs a percentage.