AFR Corrections do not make sense - log attached

[jayrex]

Basically my Command Fuel Final value is not driving my afr corrections or learning values correctly. When its richer than target it keeps adding fuel.

Its almost being ignored or modified elsewhere.

 

Is Command Fuel Final the actual final value or are there further modifications to that value during corrections. What could I be missing?

 

I'm using Cobb ATR to tune. I've been doing it a while and I am familiar with just about every table. This happens with gas or E85, pretty much 100% of the time. I can't find anything that would cause this significant of a difference.

05 LGT - lots of mods, big injectors, namebrand fpr, all the fuels.

 

Example: Command Fuel Final is say 14.7 while cruising, but I can't hold anything leaner than 13.9. Idle is the same. open loop targets appears unaffected by the issue.

My Wideband matches my stock sensor.

Thanks for any help

[solidxsnake]

In closed-loop, I believe there are some other compensations related to AF3 (rear O2 sensor) for emissions reasons. Maybe that's causing some of the issue (that's why your measured AFR is fluctuating).

[jayrex]

I believe I zeroed those out to eliminate that, but I will double check. Thanks.

EDIT: Yes they are all zero, any other possibilities?

 

There are a few tables with some slight corrections possible, but nothing that would show .8 to 1.0 rich.

Like Closed Lop Fueling Target Compensation Tables and TPS fuel Adder Tables.

I believe all those calculations are taken into account to create Command Fuel Final.

Edited August 15, 2019 by jayrex

[jayrex]

I posted over at our forum-brother Nasioc to get some more insight.

I ended up figuring some stuff out. Its not epic, just an oversight on my part.

 

I started hijacking the post around #20

https://forums.nasioc.com/forums/showthread.php?t=2857248

 

I'll post my take-aways so if others stumble onto this thread.

 

 

From other thread:

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So my main realization is that Comm Fuel Final is definitely not the same as Closed Loop Fuel Target(CLFT). I think that's my biggest mistake here. It looks like you cannot really the dictate CLFT. You are kind of at the mercy of the ecu?

 

CLFT logs much closer to my actual AFR and is certainly driving the corrections and trims. Maybe others can learn from that mistake.

 

I bet the rest of the discrepancy has to do with the ecu and the magical rear 02 sensor even though I have them zero'd out. Or maybe its just poor injectors settings.

 

I did just try turning off closed loop completely and it made a huge difference. I feel like you can actually see the result of adjustments and control the AFR Targets. Tip In is even easier to see.

 

With open loop only, the AFRs are sitting pretty good, I just need a little better MAF calibration on the low end(a bit too lean). I feel like running open loop 24/7 because of the better control. It may not be the best idea longterm, but we'll see how it works out for a bit.

 

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[xt2005bonbon]

So now my turn to thread jack you

 

 

Exactly which table(s) do you modify in order to improve your long term fuel trims across the board?

[jayrex]

So now my turn to thread jack you

 

 

Exactly which table(s) do you modify in order to improve your long term fuel trims across the board?

 

Lol you can have it, I'm done here.

 

You should be able to clean that up using the maf calibration in the real-time tables folder.

 

You can just multiply the effected cells with x0.95 for 5% less fuel or x1.05 for 5% more. You probably don't want to tinker with the values in open loop unless you have a wideband to read the afr accurately. So like Maf values 80 g/s and lower. Thats about where the fuel trims stop and open loop starts. Smooth out any changes to 1 or 2 adjacent cells.

 

I use the trace function in Cobb ATR so I can see where I'm idling right on the table. You'll need to log those values to see them at higher values.

 

I don't know a lot about opensource, if that's what you're using, but its going to be the same table.

[xt2005bonbon]

Awesome. I will look into it.

[xt2005bonbon]

Just to follow-up... Thanks OP for your explanation about MAF scaling. I have already done a couple of revisions to my MAF scaling. Fuel trim corrections are now hovering right around 0% pretty consistently across the board . Note that I did not change anything above 40 g/s. It's really easy to do actually.