[cwtt]

My question is simple, however I have a feeling the answer is complex.

When does the stock ECU switch from closed loop to open loop?


Is it based on:
Throttle position input
RPM level input
Airflow meter input
Speed sensor input
????

Any input would be greatly appreciated.

I want to do some tuning on my SAFC, but I want to make sure I am not touching any part of the closed loop fuel mapping.

 

[supra400hptt]

http://www.supraforums.com/forum/showthread.php?t=218023&highlight=open+loop

http://www.supraforums.com/forum/showthread.php?t=203026&highlight=open+loop

http://www.supraforums.com/forum/showthread.php?t=68426&highlight=open+loop

http://www.supraforums.com/forum/showthread.php?t=68426&highlight=open+loop

You can use the search function and search old posts to get answers to many questions. Throttle postion seems to play the biggest role.

 

[jam98tt]

Go to this site,it has a lot about tuning.If you want you can read the whole thing or go to page 9 and read ECU Operating Modes.

http://www.gadgetonline.com/U-Tune.pdf

 

[chevyeater-on-sf]

Go to this site,it has a lot about tuning.If you want you can read the whole thing or go to page 9 and read ECU Operating Modes.

http://www.gadgetonline.com/U-Tune.pdf

From that PDF:

I tuned a customer’s truck with one of URD’s Supercharger Performance
Upgrade Kits on it. The customer was very excited about the dramatic increase
in performance, but the next day he called with a concern. He has a PLX wide
band unit hard wired in his truck and he told me that his engine was seriously
leaning out at high RPM. He said that he tested this about 20 times and it was
always the same. This is kind of like hitting your thumb with a hammer. If it
hurts really badly the first time, you do not need 20 more times to confirm it, hurt
hurts…

:lol: :lol: That was good.

Regarding the question posed, one of the few things those blinky light A/F meters are good for is knowing when the ECU is in closed loop. With a SAFC, you ought to be safe setting the high/low throttle setting to 80%.