pretty much as the title says:

basically i have heard that closed loop on the oem ecu means 14.7:1, and everything richer than that is open loop in nature.

i have also heard that ecutek is currently the only reflash technology that can target a value LEANER than 14.7:1, for closed loop operation.

are these suppositions true?

for reference:

http://forums.nasioc.com/forums/showthread.php?t=837419
http://forums.nasioc.com/forums/showthread.php?t=890303
http://forums.nasioc.com/forums/showthread.php?t=950029

IMHO, this is not true.

The ECU operates in closed loop until it encounters commands to switch to open loop. These commands are based off of calculations/readings of realtime engine/environmental data and preprogrammed values in the ECU calibration. For example, the ECU is targeting 14.7 just driving down the highway. However, the primary fuel table in the STI also has values less than 14.7. Obviously, the ECU shouldn't be allowed to target very rich AFRs because the stock O2 sensor isn't capable of that accuracy. However, the 'near wideband' in the STI is capable of targeting around 14.7 without a problem. SOA has programmed specific algorithms on when to jump out of closed loop and go to open loop. I won't sit here and try to pretend like I know them all. I don't. However, beyond a particular throttle %, the ECU switches to open loop. Once a particular calculated load value is exceeded, the ECU switches to open loop. One a particular RPM is exceeded, the ECU switches to open loop. All of the things together, allow the car to target non 14.7 AFRs in Closed loop ... but allow switching to open loop before targeting very rich AFRs.

In my car, I can easily target rich AFRs in closed loop. On the STI the long term and short term fuel trims go to 0.39 when the ecu switches to open loop operation. I can cruise at 13.xx with long term and short term fuel trims in operation ..... no problem. In fact, for awhile I had my idle configured for 14.07 AFRs just for experimentation with the bigger Nismo Injectors. The ECU had no problem maintaining that. I can easily do this again and grab a log if you would like.

Now, targeting greater than 14.7 (leaner) .. is not possible with StreetTUNER. I physically can't enter in anything leaner.

t

for UTEC, you cant do anything to natively target an AFR other than 14.7...you can, however, trick it into doing other things for you. the only reason you have to target 14.7 with the UTEC is because that is how the stock ecu is set up.

i havent played around with my ST in a long time, but from what wolf is saying apparently in one of the newer releases, they allow the closed loop target to be modified (richer only).

by nature closed loop will target whatever it is set to target based off of what the current AFR is (from its O2 sensor reading). it could be 1:1 or 100:1. alternatively, by nature open loop will just dump x amount of fuel for y amount of air mass...and in the case of the stock ecu, this is actually a calculated estimate AFR value.

much like the UTEC, the stock ECU will kick in to open loop based off of certain conditions such as TPS, RPM, calculated load, etc.

Tim-

How did you change the CL target? You can change injector scaling and MAF calibration, but ultimately, the car will make it's way back to stoich.

Mike