RomRaider

Ok I have not seen anyone do this yet. I read you could just trick out the ECU with the O2 sensor scaling.
I just put together a new scaling to try. Before I use it I just wanted a second set of eyes to look at it to make sure I did it right.
The only problem is the ECU should be reading the leaner AF as 14.7. I have no idea how this will effect other areas of the fuel maps.

I expect you'll max out AF Correction #3 on the positive side and you'll see trouble code P2096 - Post Catalyst Fuel Trim System Too Lean Bank 1.

I also expect your AF Learning #1 fuel trims will be reduced by about 10% (i.e. if they are zero now, they'll end up being about -10 after your change). You'll need to redefine AF Learning #1 air flow ranges such that the rightmost AF Learning #1 is never updated (i.e. stays zero). Otherwise, it is applied to your open loop fueling calculation and you don't want to have your fueling reduced by 10% across the board in open loop.

You may have to simulate your rear O2 signal. You can disable P2096, P0420, etc. but the car may still add fuel back to satisfy some unknown logic with regards to the rear O2. I know the car will run rich if you take your rear O2 out of the exhaust (so it always reads lean condition).

The LC-1 or LM-1 analog out, set to simulate the toggling signal at 16.22:1 AFR would do it. I use this to simulate my rear O2 on my own car though I just run 14.7:1.

You will either have to fudge your MAF or fuel injector scalar to get fuel trims back in line. I'm not sure which is worse.

I would probably adjust your fuel injector flow by 14.7/16.22 (tell the ECU they flow less) then either remember to make your open loop fueling maps extremely rich (add about 1-1.5 pts)), or change the conversion factor on the open loop fueling maps by 14.7/16.22.

There is no extremely elegant way to do it.

I am just using romraider for CEL's and below utec crossover(ie. cruise only). I have run lean burn with the utec but because the utec reads TPS from the pedal and not the throttle body you can't use cruise control and get the leaner AFR. Because i use the utec when I am >23% TPS I don't have to worry about any changes that may be needed to the OLF map.

This is an excellent idea. What do you do about the heater circuit?

I disagree here. The negative fuel trims during closed loop are more or less what he's aiming to do and not a problem. The only worry is that the fuel trim applied during open loop needs to be zero. He should not alter MAF or injector scaling.

He will probably need more cold-start enrichment. And he'll definitely need to increase spark advance in the cells where he's in closed loop AFR control.

Does the modified O2 scale look ok? If I did it right the ECU should be targeting 0.24mA instead of 0.0mA. Which would correspond to an AFR of ~16.2:1.
I am having trouble with ECUflash not seeing my openport 1.2 cable so I have not been able to flash the new O2 scaling to my car.

That part looks OK, although 16.2:1 is at the upper end of how lean you can run.

I'd get a benchmark of runs logging Roughness with your current flash and then log Roughness after your flash to see whether you're misfiring because the mixture is too lean.

Like I said i have done lean burn with the utec. I experimented with AFR's from 14.7 to 19. After a lot of tweaking I ended up at 16 to hit max mileage.

And how much did that actually gain?

Leave the O2 sensor ziptied under the car. You just splice in on the signal wire, everything else stays attached. I actually cut the wire at the ECU harness. Maybe a bit daring, but you can't just T it in. You can do it at the sensor. I think you could also fake it out with the correct resistors. The actual heater power wire would want to blow a lot of current, though so it might take a hefty resistor. I haven't done this.

I recall that klatinn at Innovate once suggested that substituting a brake light would work, but I haven't tried that, either. It'd give the car a nice under-glow, though.

The car is targeting 0.25mA from the stock sensor. I have a 3 tank baseline MPG of 25mpg.

nice mark. it looks like it might just work.

it's a bit easier for me with my 16 bitter.

I will see how it goes. The biggest problem is my WBO2 sensor died. I am just using the stock A/F sensor read through the Utec to see the changes in AFR.

Hey good works guys, I've found the same things with gas mileage increases, no problems with rear o2, but occasionally, I get CEL with no code. I haven't narrowed in on it yet. But it may have to do with the AF learning circuit like mentioned. Anyway, I have been working on doing this sort of thing for ALL CARS with narrowband o2's and I came across a product called the EFIEE, which you could add to your rear o2 to "richen up" the signal so it doesn't try to add fuel, if that is still a problem when it reads lean. BTW I started at 20 mpg and now ave 25 with very little highway miles. My target is very close to your's as well at roughly 16.5. I've seen reports from 15.7 - 16.5 for best economy, but from my experiments, EACH car and circumstance is different. I currently haven't modified the maf scale, but have watched it, I run to about 2.6v before I pop out of closed loop, so if you guys find it works well, I would go that route but for now, I don't think I'll mess with with my stock scaling. Oh, I almost forgot, I have noticed, on two occaisions, cold motor, cold morning, ever so slight lean hesitation in the first minute (like first 1/2 mile) driving. What would I change to fix this?