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Can anyone take a look at my log file and tune? I switched from a truck intake to a fast 78 on my engine,and i went out and did some data logging. my engine was previously tuned with the truck intake. Anyway, I logged about 20 minutes of driving with a few wot runs. During my first wot run, my lc2 wideband recorded an afr of 12.7.....i made a few more runs,and at wot my afr kept getting progressively richer down to 11 to 1 afr. what gives?
First off, need to figure if this is intent or outcome. What
was the AFR commanded doing, while this creep on the WB
is seen?
Cat overtemp protection (COT) is one actor which rolls on
enrichment after time-at-load, progressively and hangs
around for a while once triggered.
Your AFR commanded, if different between PE and the COT
settings, could provide that clue.
Other things like ECT, IAT fuel adders can also be in play
and follow motor activity at some lag. You should be able
to log many of these adders, to see; just takes time and
a methodical approach to debug.
1. I see some "steps" in your a/f ratio, which tell me that your fuel map may not be smooth, or the maf is dirty as in #2,
2. Check your maf ground/shielding if you suspect the maf sensor is picking up noise that is reflected in it's log (there is often a grounded shielded wire for the ECU and the chassis, some maf have both), or try cleaning it and cleaning the air filter and all plumbing in front of the maf.
3. As an engine's internal parts get hotter, that is the intake valve, piston surface, cylinder walls, engine oil, intake ports, etc... This will reflect in the air density and the engine may run richer. There are compensating steps taken with the ECU (such as IAT and CTS adjustments) but these are global and rarely reflect actual increments (your IAT does not directly accurately reflect retained temperature in the cylinder wall for example).
4. Furthermore, as devices heat up, fuel pumps, the fuel itself, the wideband sensor, these will also affect your recorded and established a/f ratio, i.e. resistance in electronics changes with temperature. Especially a wideband that gets too hot (around 900*F-1100*F they begin to wander more rich, with 1250*F They become completely undependable and some such as AEM will continue to read 11:1 while your engine is 16:1)
most of these tiny changes are lost in a sea of global fuel, and maf correctly functioning maf sensors are traditionally very reliable. The couple of percent here or there may only give you a deviation of 0.25 to 0.50 a/f maximum from ideal settings during WOT, however during idle the situation is quite different as a slight wander with a large injector can lead to major differences in idle a/f ratio. The maf itself has a resolution based on the actual flow vs total flow, when actual flow is very low compared to total flow, and the maf itself is very large (many people upgrade them to larger sizes) the resolution may become very low for idle situations that call for more carefully planned duct work or other ideas.
Here is what we have so far, i took my maf out and cleaned. I went for another ride, and logged commanded AFR, and it appears that my afr is just running richer than commanded
Alright so you see some 11.0's and 10.8's, not a bad starting point. You appear to have 26* btdc also, is that an OEM advance? Seems like a lot to me but I do alot of turbocharged engines so maybe I am just ultra cautious.
In any case, your fuel looks valid, that is it looks stable; applicable. All you need to do now is lean it out a little bit, bring it back little by little to where you want it. Depends on your compression ratio but maybe 12:1 is a very safe starting point to pick up power.
I recommend you do it on the dyno, so you can see the difference in power stepping from 11:1 to 12:1 and perhaps 12.8:1, as you will find a diminishing returns at some point, you might decide to keep it a bit on the rich side for safety (if this is a daily driver). In other words, for tuning on the street has its uses, it is not the best place to lean the engine out for it's final power, since A: you cannot see the power increase and B: you have no way to verify the accuracy of your wideband sensor, both very good reasons to seek a chassis dyno for this final step.
I wonder if your Wideband is reading low. In the area where your stock O2 sensors are oscillating (which is normal) the Wideband should be reading around 14.7. Yet the green line is only slightly higher there than when it is reading 11.18 in your last picture.
Why not post your log file so that we can move around in it.
Alright so you see some 11.0's and 10.8's, not a bad starting point. You appear to have 26* btdc also, is that an OEM advance? Seems like a lot to me but I do alot of turbocharged engines so maybe I am just ultra cautious.
In any case, your fuel looks valid, that is it looks stable; applicable. All you need to do now is lean it out a little bit, bring it back little by little to where you want it. Depends on your compression ratio but maybe 12:1 is a very safe starting point to pick up power.
I recommend you do it on the dyno, so you can see the difference in power stepping from 11:1 to 12:1 and perhaps 12.8:1, as you will find a diminishing returns at some point, you might decide to keep it a bit on the rich side for safety (if this is a daily driver). In other words, for tuning on the street has its uses, it is not the best place to lean the engine out for it's final power, since A: you cannot see the power increase and B: you have no way to verify the accuracy of your wideband sensor, both very good reasons to seek a chassis dyno for this final step.
Thats not an oem tune, My engine is a head cam 6.0 that I had professionally tuned. When it was tuned, i was still using the gen 3 truck intake, since then i switched to a fast 78, and im trying to get the tune dialed back in.
What gear are you in for these? Speed seems low. Should be 4th for a t-56 and 3rd for an A4 I believe.
Doing a pull at low speed goes by too fast. Zoom into the WOT range as well. You can zoom in enough to make the WOT pull almost the whole screen wide.
Also overlay Commanded AFR onto the same section as the WB. This will make a comparison much easier.
I have a A4, Everything i logged was done on the street, so all of the WOT pulls that I logged were done in 1st and 2nd gear. For safety reasons, i really cant log a 3rd gear wot pull on the street.
Next time that i log data, i'll overlay commanded afr and actual afr on the same section.
I wonder if your Wideband is reading low. In the area where your stock O2 sensors are oscillating (which is normal) the Wideband should be reading around 14.7. Yet the green line is only slightly higher there than when it is reading 11.18 in your last picture.
Why not post your log file so that we can move around in it.
In my first post, i posted my tune and my log file, But i'll attach another log from a seperate test drive. In the log file above, i wasnt recording commanded afr, In the log in this post, i was recording commanded afr.
What i really find strange is that in my first couple of WOT pulls, my WOT afr was 12.8, which i consider about perfect. But ever since then my WOT afr dropped to around 11. Thanks for taking a look at my log file, i really dont know how to interpret the oscillation of my narrow-band o2s
Sorry, even with your .cfg file I cannot get your Wideband AFR to show.
Perhaps one of the tuning experts here can confirm, but in the area where the stock O2 voltage is oscillating, I think the wideband should be reading around 14.7 (lambda 1.0),
Probably best for me to step out and let one of the more experienced members help you further.
This is a very basic observation and may be way off, but I noticed your long term and short term fuel trims are negative and in some cases rather high.
I wonder if simply multiplying only your long term trims into your VE table while still keeping your short term trims negative would alleviate the problem.
10-09-2015, 08:50 AM
Wot runs get progressively richer 
