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STFT -5% and AFR targets

Practical Reflash Tuning

Relevant Module: Advanced Tuning > MAF Rescaling

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Discussion and questions related to the course Practical Reflash Tuning

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Hi Guys,

I have a HSV VXR i have tuned with ECM titanium with a standard MAF but with a modified airbox. I dont have a MAF table available in ECM titanium but my STFT is showing -5% to -8% in cruise usually closer to -5% so I thought this should be ok even though not ideal, However when checking my AFR under wide open throttle my AFR meter is showing 0.69 Lambda instead of the requested 0.75 Lambda. Is this just the error that is expected because I have accepted around 5% error in the MAF scale? Given that I dont have access to a MAF scaling MAP in ECM Titanium should I just set the requested Lambda under high load leaner than what I actually want to compensate? It seems even if my MAF was within the 5% that is deemed acceptable that a 5% difference in AFR would need to be accounted for somehow or am I missing something?

EDIT, also this is a ME7.6.2 ECU so it only has narrow band so at high throttle setting it goes into open loop mode using only the MAF and ECU tables to set the AFR. is the +-5% rule more applicable to ECU's that can adjust fuel trims through out the load range? Will my LTFT adjust for this over time or is that only applicable to newer ECU's as well?

Thanks guys

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