Started LQ4 swap for first time and runs really rough, long term fuel trim way off

[joecar]

The pressure difference across an injector determines its flowrate...

with an manifold-referenced FPR:
pressure on top = 58 psi + MAP.
pressure on bottom = MAP.
difference = 58 psi = constant

constant pressure difference means IFR table B4001 will be flat.


More precisely, mathematically, see here: Calculating-Injector-Flow-rate

[ja_engineer]

I swapped injectors out this morning and now the car idles/sounds much better and the fuel trim looks ok to me. However, when I give it a little throttle it starts to stall/stumble and these stumbles are timed to the commanded AFR going from 14.68 to 14.03 when I am looking at the scan tool dashboard. I have uploaded a log of when this occurs. Do you have any ideas what might be causing this?

[joecar]

Looks like transition from base spark table to HO spark table is too great.

[ja_engineer]

I am running the stock tune except for the segment swap to manual, the maf tables for the 85 mm maf (engine did not come with the stock maf) and the new injector data (copied from stock ctz). Based on that I was not anticipating have to adjust spark tables. Do you have a recommendation? I just hooked up the wideband on and it is idling around 16.2 afr and goes leaner with throttle.


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[joecar]

I am running the stock tune except for the segment swap to manual, the maf tables for the 85 mm maf (engine did not come with the stock maf) and the new injector data (copied from stock ctz). Based on that I was not anticipating have to adjust spark tables. Do you have a recommendation? I just hooked up the wideband on and it is idling around 16.2 afr and goes leaner with throttle.


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If it's running from the MAF then the MAF table will need correcting.

The MAF table is sensitive to not only the MAF but also its plumbing.

[ja_engineer]

Is there a general increment to beginning the maf table adjustment? Or do I just go a couple percent at a time until I get a reasonable AFR.


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[joecar]

Take a log, apply the transient filter (to eliminate data during which throttle moved), make a map of average of LTFT1 and LTFT2 (as a BEN), and apply this to the MAF table.

[ja_engineer]

I found that the intake gaskets are leaking and causing bank 1 to go lean so once that is fixed I will work on the maf. With that being said what does "as a BEN" mean?

Thanks


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[joecar]

..., make a map of average of LTFT1 and LTFT2 (as a BEN) ...

Average of LTFT's is (LTFT1+LTFT2)/2 and had units %

this as a BEN (i.e. multiplier) would be 1+(LTFT1+LTFT2)/200 and is unit-less.

[ja_engineer]

Ok so I fixed the vacuum leak and played with the maf table some but I still get this stumble/surge under constant throttle. I have attached a video of it but I can't figure it out.