AFR in Closed Loop

[Toyota John]

Has anyone messed with the afr's in closed loop to increase MPG? I was reading on the mr2 forums that on closed loop they were running e85 as lean as 17 afr (on a wideband set for pump gas) to try to get some of the mpg back they lost. I don't know and think that i should run 93 pump that lean because egt would be high but i think we could run it leaner the 14.7 standard afr in closed loop fueling? Anyone try? I bet we could get close to 40 mpg?

[Kodename47]

I don't think you can set the CL fueling tables to leaner than 14.7. The only way to do it would be to offset the O2 sensor scaling.

[arghx7]

For what it's worth, I did it a long time ago on a 2005 Legacy GT with an older version of Cobb Accesstuner. There were some tables labeled as closed loop target AFR on that version (this was before Bill from RomRaider joined Cobb and redid a bunch of stuff). I leaned it out enough to help gas mileage but not enough to cause misfire. I just dug up an old screenshot of a log I made.

[gonzo]

Originally Posted by Toyota John

to try to get some of the mpg back they lost.

This would be amazing. I'm thinking of flashing back to 91 with this e85 price increase. It was $3.20 just a few weeks ago and now $3.70. And I'm only getting 14-16 mpg

[Toyota John]

I talked to my turner friend and he said the only way he got it to work was to turn off O2 feed back. But this wasn't on an frs. I think he said it was on an older sti. The mr2 guys that were doing it didn't have the ability to change closed loop fueling but they could turn it off and run from just the fuel table. I would like to try and see if I can change closed loop and have it make a change.

[Kodename47]

Originally Posted by Toyota John

I talked to my turner friend and he said the only way he got it to work was to turn off O2 feed back. But this wasn't on an frs. I think he said it was on an older sti. The mr2 guys that were doing it didn't have the ability to change closed loop fueling but they could turn it off and run from just the fuel table. I would like to try and see if I can change closed loop and have it make a change.

AFAIK you can't set the open loop fuel table to leaner than 14.7 too so even if you running full time open loop you can't do it. Unless of course you skew the MAF scaling....

[Toyota John]

I tried to change the closed loop fueling table and nothing happened. AFR stayed at 14.7. I guess that table does nothing? The main fueling table can not be changed to anything higher then 14.7 ether. Only lower numbers are accepted.

[Kodename47]

Originally Posted by Toyota John

I tried to change the closed loop fueling table and nothing happened. AFR stayed at 14.7. I guess that table does nothing? The main fueling table can not be changed to anything higher then 14.7 ether. Only lower numbers are accepted.

From what I've read on previous ECUs, the CL fueling table is basically CL enrichment. There was a table to set the base CL fuel target as @arghx7 said. However this may not be the same on our ECU, it's not been defined yet if it is.

[Ross]

You would have to completely disable the factory closed loop system to do this. It is doable, I have not done any long term testing so I can not give a good answer on reliability.

[spitfire481]

Originally Posted by gonzo

This would be amazing. I'm thinking of flashing back to 91 with this e85 price increase. It was $3.20 just a few weeks ago and now $3.70. And I'm only getting 14-16 mpg

man thats low mpg. my average on 93 pump is 30.5. average on e78-85 is 24. i reset it once a week and calculate when i fill up so i know the gauge is somewhat accurate. my driving is about 50/50 highway/city.

[mad_sb]

Originally Posted by Ross

You would have to completely disable the factory closed loop system to do this. It is doable, I have not done any long term testing so I can not give a good answer on reliability.

Actually, you don't have to disable anything.

you can do this using the coolant temp based target offset tables. I forget the names right now. As others have said the closed loop target afr is not what the name would indicate and you cannot set a value leaner than 14.7 without error. I saw some strange fuel trim stack-up when i messed with it and have not bothered to try again.

[Toyota John]

The more I learn about this car the less i seem to understand.

[Kodename47]

Thread revival. Thought that this is the best place for this. Having some wierd closed loop fueling issues that I've finally decided to tackle, seems like the ECU targets around 13.8 for a while before reverting to the CL fuel table target, which I have set mostly to 14.7. You can see in the graph below that the AFR tracks pretty well, but it always goes to 13.8 when changing to Fuel System Status 2.

Blue is Commanded AFR / Yellow is AFR


This chart the load and RPM are not changing much, in fact the earlier part of the chart is at lower RPM and loads so should be hitting 14.7.

I have tried changing the minimum open loop enrichment value and the closed loop targets are never that rich.

Map is A02G

I'm no running a rear O2 sensor, I wonder if that makes a difference?

Ideas?

[504]

Originally Posted by Kodename47

Thread revival. Thought that this is the best place for this. Having some wierd closed loop fueling issues that I've finally decided to tackle, seems like the ECU targets around 13.8 for a while before reverting to the CL fuel table target, which I have set mostly to 14.7. You can see in the graph below that the AFR tracks pretty well, but it always goes to 13.8 when changing to Fuel System Status 2.

Blue is Commanded AFR / Yellow is AFR


This chart the load and RPM are not changing much, in fact the earlier part of the chart is at lower RPM and loads so should be hitting 14.7.

I have tried changing the minimum open loop enrichment value and the closed loop targets are never that rich.

Map is A02G

I'm no running a rear O2 sensor, I wonder if that makes a difference?

Ideas?

Did you find a solution to this? I'm having similar issue as my fuel goes down to E3 (flex tune). 13.7 commanded on light cruise then when idles, it shoots back to 14.7, it's pretty annoying

Certain, my closed loop fuelling is not targetting lower than 14.7 and temp comps are all set to 0