Quote:
Originally Posted by Daox
If your engine leaned out 5-15% your O2 sensor would see that and correct for it.
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What's happening is the AFR measured at the O2 sensor is around 10% or less, likely less on a much smaller engine (I said 15% so people wouldn't get on my butt as they have on here for some little discrepancy) over the base air volume/time tables given by the OEM air box MAF. When we throw in a CAI that increases the volume of air to the MAF at the same time, the MAF actually reads the same in measured Hertz for larger volume. Unless the long term fuel trims can be changed enough by the O2 sensors to warrant dropping out of closed loop for part throttle driving, the Hz measurement from the MAF to the ECM will continue to be the main fuel adder map. It runs lean.
Edit - If I didn't explain this well just let me know, the O2 sensor reading and the actual AFR are different. The ECM commands a certain AFR to the O2 sensor, which is what the sensor will show. The actual ratio of air/fuel will be slightly lean.