Quote:
Originally Posted by Superturnier
I've been wondering why an (older) EFI system switches between lean and rich fuel mixture instead of keeping very close to 14.7:1 ratio. (the 14.7:1 is said to be best for killing emissions) Is it because the control system is not capable doing it or is it for the catalytic converter that actually needs to have different poison after another poison to work properly? Not just steady mixture all the time?
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The original closed loop systems used a O2 sensor that really only detected two states: Lean, and Rich. If the sensor said rich, it would get leaned out. If the sensor said lean, it would richen the mix. The cross over point for these sensors was 14.7:1.
Is this what you meant by switching between lean and rich? These systems were fairly good at holding close to 14.7:1.