|
We lengthen the tube for the upstream O2 sensor to keep it from reading way too lean, leading to STFT and LTFT adjustments that make it run too rich... that little pocket of air makes for more stable readings when you're installing a new header with high flow. At least that's what I *think*. I could be wrong.
The downstream O2 sensor, as far as I know, is only used to detect if the cat is working or not.
|