i think someone who specializes in flashing ECUs... i have no experience... but i do know that the SRT-4 PCM OPEN LOOP on my S2 PCM is identical to my S0 PCM OPEN LOOP and dumps in the same amount of fuel (granted the fuel maps are slightly different because of injectors - the % capacity used is lower for the bigger injectors (682s) to give the same amount of gas) the CLOSED LOOP is entirely different... the CLOSED LOOP on the S2 PCM versus the S0 PCM has boost gain map increases, boost peak increases, and several other options. CLOSED LOOP occurs on my SRT-4 with several conditions but typically whenever i hit above 3500rpms (6500 redline) even with 0 boost... now if 10psi is hit anywhere in the rpm range then it goes into CLOSED LOOP... and if the car's engine temp gets over 180- degrees F then it goes into CLOSED LOOP and basically CLOSED LOOP on SRT-4s is for performance and monitors every sensor and makes sure all engine parameters are at peak performance where as OPEN LOOP is more for economy.

so basically if an OPEN LOOP is modified/reflashed you could see differences in mpg if just cruising but if you're in CLOSED LOOP you probably have a very good chance of seeing changes. i usually try to tune my car to about 11.4 AFR at redline and i seem to be getting great results just using a map clamp, fuel return line, FPR, and UEGO w/ datalogger.


can someone else with experience explain this better than me... i'm still a bit of a novice with PCM/ECUs.