tuning with a 3 speed automatic, 2nd gear has different AFR than 3rd gear

[Matt_lq4]

When I go for my scans to tune the maf in 2nd gear and input the data into my tune, my maf lambda error % is almost dead on in 2nd gear. Unfortunately when I wind out 3rd gear from similar rpm until my limiter, I get more lambda error % despite being at extremely similar maf frequencies.

The opposite is true when I am on a dyno in 3rd gear or on a highway and scan WOT from 2500 rpm to my 6600 rpm redline and input the data into my tune. In this situation when in 3rd gear, lambda error % is very good as I scanned in 3rd but my 2nd gear lambda error % suffers.

Is this just the reality of not having closed loop feedback at WOT/PE?

Attached is a blended scan and tune however I suppose it doesn't matter that it's not MAF ONLY as after 4000 rpm my maf should be responsible for fueling.

[Matt_lq4]

Does this sound like a maf turbulence issue, injector data issue or a normal occurrence?

[dermotw]

Well, as far as I know, MAF issues with flow variations show up better at idle/cruise (they do show under power as well). You don't appear to have anything happening at low rpm... Your log MAF values look a bit odd though, specifically the way it "jumps up", initially. The variations later on don't look so unusual to me, although they are quite sharp, which isn't how mine looks, see below, same scale, see how mine still changes, but more smoothly, I have a honeycomb as well - anyway, hopefully someone who knows more than I do will say! One thing is, the IAT is quite likely different between a static run and driving, and it has some impact, it also shifts during a run, if you were static/moving slowly beforehand...

Capture.JPG

[Matt_lq4]

Well, as far as I know, MAF issues with flow variations show up better at idle/cruise (they do show under power as well). You don't appear to have anything happening at low rpm... Your log MAF values look a bit odd though, specifically the way it "jumps up", initially. The variations later on don't look so unusual to me, although they are quite sharp, which isn't how mine looks, see below, same scale, see how mine still changes, but more smoothly, I have a honeycomb as well - anyway, hopefully someone who knows more than I do will say! One thing is, the IAT is quite likely different between a static run and driving, and it has some impact, it also shifts during a run, if you were static/moving slowly beforehand...

Capture.JPG

If it is turbulence then it's a nuisance but I'll have to live with it. I look for 100% perfection but sometimes you just have to accept the results you get

[IARLLC]

I have noticed on several occasions that I will have exactly 12.7 or 12.8 all of the way through second then as it continues up through third it starts to show me 12.9 or 13. Since I have seen it several times and I know my fuel system is up to the task I have figured that the richer PE fuel mixture may affect the wb sensor after several seconds straight. I have yet to lock it in third and start out low to see if it starts to show leaner mixtures after several seconds in PE. One other idea would be to check the injector pulse-width at the exact same RPM/cylinder airmass when you are getting strange lambda errors in both second and third. I am wondering if your actual AFR is not changing....just being reported inaccurately.

[mbray01]

because loading is different, afr's can and will change, When tuning I try to tune from the highest gear possible. Now having said this afr changes you see in the trims should not be huge, typically under 5%, but there will be trim differences between gears.

[Montecarlodrag]

It's not MAF turbulence, the same thing happens with SD. I think there are a few tables that we don't have access to.
For the same KPa and g/cyl the AFR is richer at high gear even when it's referencing the same MAF or SD cells.
I have seen up to 0.5 AFR difference with all adders disabled.

[Matt_lq4]

It's not MAF turbulence, the same thing happens with SD. I think there are a few tables that we don't have access to.
For the same KPa and g/cyl the AFR is richer at high gear even when it's referencing the same MAF or SD cells.
I have seen up to 0.5 AFR difference with all adders disabled.

Wow, I was about to play with my injector data as I was going nuts trying to see where I messed up. I am more at ease now

[Matt_lq4]

Ok thanks mbray01, I'll scrap 1st and 2nd gear scans and tune based on 3rd gear (1:1) only when at WOT as more accurate data gets derived here and that's as good as it will get.