Wideband reading lean, LTFT still pulling fuel

[Smash]

New tuner here, recently installed speed engineering LTs and air raid intake tube on my L83 truck. I am in the process of scaling my MAF and noticed when in open loop my idle is very lean according to my wideband but when I look at my LTFT is is pulling 10-15% fuel. I have add 5% to my MAF in the idle area and LTFT is better but wideband is still reading lean 1.03-1.07 lambda. Any suggestions on what to look for?

Thanks

[Haans249]

Hello, welcome. If you’re in open loop, then there are no fuel trims, so I’m guessing you mean closed loop.

If LTFT are pulling fuel, that means you need to reduce your MAF in those areas (reduce fueling), not add more. If you add more fuel, your trims will go even more negative. When your O2’s are making fueling adjustments, you cannot tune with your wideband, you have to tune with Short Term Fuel trims, so instead of using eq error, you use STFT, set to % for your MAF scaling. I’d also suggest two graphs, one for idle by adding filters specific for idle (vehicle speed 0), and ECT 190+, and another with ect 190+, and eq ratio less than 1.1 as filters to account fir DFCO.

[Smash]

Thanks for the response. When you say EQ ratio less than 1.1 do you mean anything under 1 lambda

[Haans249]

Thanks for the response. When you say EQ ratio less than 1.1 do you mean anything under 1 lambda

I am referencing logging your Wideband that typically has the label "WB EQ Ratio 1" in VCM Scanner. That is read in Lambda, so when you add your filter, you select that PID (WB EQ Ratio 1) and the data is lambda, so anything above 1 is lean and anything below is rich. I'm suggesting a value of less than 1.1 (removes any data that is above 1.1 when it populates your graph) to try and filter out transients of throttle and/or DFCO, though there are other exact filters for throttle transients as well. This is what I use for my filtering:

(2016 Camaro SS)==> [50090.156.slope(1000)]<5 AND [50090.156.slope(-1000)]<5 and [50010.242]>190 and [50127.238]<1.1

50090.156 = Throttle Position
50010.242 = ECT
50127.238 = WB EQ Ratio

So, when setting up your filters, you can either copy and paste the formula above or if that doesn't work for some reason you can build the filtering using the translation above.

Hope that helps!