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Tuner
Active Mufflers
I have noticed that when I am driving in 1st-5th gears my AFR and Maf appear to be really good. I have stainless works long tubes and no cats with the OEM GT350 Catback. Shifting to 6th closes the muffler valves automatically.
once this happens I immediately become 8-10 percent lean (Per O2 Sensors). Doesn't make sense to me. Mufflers open in the same MAF cells and same SD cells and the AFR is +- 2%.
could the muffler back-pressure be effecting how the 02s read?
Bank 1 and 2 behave the exact same. I cant figure it out.
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Advanced Tuner
Whats happening with commanded AFR? I'm wondering if its programmed logic to aid in fuel economy.
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Tuner
The scavenging effect will be impaired with the increased back pressure. There will be less unburned fuel escaping during overlap. I don't think running a bit lean at cruise will hurt anything, especially since the cats are gone.