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In this module, fuelling was increased in two ~10% steps (via pulse width) with everything else held constant — timing, target boost and fuel pressure unchanged. Across all three tunes the MAP stayed constant at ~38 (23 psi), and the exhaust AFR was described as capped at 19.5:1 (≈ lambda 1.34).
Here's what I can't reconcile: if MAP stayed constant, the air mass entering the cylinders was essentially the same across all three runs. With the same air but more fuel injected, I'd expect the AFR to go richer (drop below 19.5:1), even if only slightly. Yet it's presented as staying at 19.5:1.
How can lambda stay effectively constant when air mass (MAP) is unchanged but fuel delivery increased?
Good catch Rafeal! The boost call/actual must have risen to meet the higher fuel contribution. Some of these older trucks had PID ceiling issues where you quickly run out of gauge resolution. Sorry for the confusion.
Thanks Nick
