closed loop and open loop switching

[minytrker]

I have a 99 vette thats maf-less but is in semi closed I guess you would call it. How often should it switch between closed and open loop and long should it take. I had a 02 sensor go bad so after changing it I was watching the 02's and cl and ol. When you start the car hot it stays in ol till you drive sometimes, other times it will switch right after you start it up. Whats making it stay in ol sometimes?

[ringram]

Seems to switch faster when driving. But not so fast at idle. Take a look at the closed loop modes, switchpoints, min and max adjustments etc.
Perhaps its because LTIT and STIT take over at idle and O2 control takes over above that?

[SSpdDmon]

The OL timer determines how long the car waits before kicking into CL. It's based on ECT at the time of startup (see B4202, B4204 and B4205). Basically, the car is allowing time for the NBO2's to warm up before trusting the information it receives from them. That's why you're in OL after startup. All of our cars do this. Those who choose to run OL just don't see it kick into CL once the timer is up.


BTW...is this a mistake GMPX? I don't remember it being there...

[minytrker]

The OL timer determines how long the car waits before kicking into CL. It's based on ECT at the time of startup (see B4202, B4204 and B4205). Basically, the car is allowing time for the NBO2's to warm up before trusting the information it receives from them. That's why you're in OL after startup. All of our cars do this. Those who choose to run OL just don't see it kick into CL once the timer is up


I understand all that, the part I don't is what is changing the amount of time before it switches? For example drove the car 25 miles, it was in CL when I cut the car off. A few mins later started the car back up and its in OL and it stayed there till after I drove for awhile and hit 40mph. Pulled back over and shut off the car. Then started it back up with a few mins like before this time it switched to CL in less than a min.

[SSpdDmon]

Mods, anyone?

http://forum.efilive.com/attachment.php?attachmentid=747&d=1152537485

[joecar]

I think that's right, ECT vs IAT.

[SSpdDmon]

Guess I never noticed the IAT part. Thought it was strictly ECT. Funny to think about though....where do the IAT's get up over 266*F on this planet? :)

[minytrker]

The car is running a little off from 1500rpm and below. All this started after a 02 got burned by the headers. We installed a new set of rear z06 o2's back in the front with the plug adapter that came with the headers. I was told the rear o2's for a z06 have a hotter heater in them and work better with headers. Is it possible that these o2's are making it run weird and keep switching from OL to CL.