Hi Greg, if memory serves, Ron Described this some time back. Idea as I recall is that in the exhaust pipe (or any pipe w/ gas or fliud flow gas thought of as a fluid) fastest flow is towards center of pipe diameter. Slower flow against pipe walls. Remember the Coanda Effect or perhaps boundary Layer effect. OK now HC molecules/particles in exhaust stream have more mass than just hot gas. These will tend to gather in gas rolling down pipe inside wall.
By adding extender to O2 sensor, we move sensor tip closer to pipe interior wall,away from center of gas stream where there is more HC and other larger molecules present than in center of gas flow. The heavier stuff against pipe walls will displace more oxygen than the lighter stuff towards center of gas flow.
In effect we are making O2 sensor tip sniff an analogue to a "richer mix" of exhaust gas, one where some less O2 is present. Theory goes that as O2 senses less oxy., it will cause ECM to trim back fuel. If you did the O2 extender, could be useful to have scantool O2 readings w/ hot engine, before/after the extender install. Also remember the caution about O2's w/ more than 50 K on 'em.
Also the Groove does not "lean out" the A/F ratio. A successful Groove will cause more complete combustion, that uses up more oxygen, so O2 sees less oxygen in exhaust. Basic rule for O2 sensor voltages is "Lean is Low" so hot engine O2 values ideally go higher voltage within the range. That's for simple O2's dont remember all the tech for newer A/F ratio type O2's and other multi-wire ones.
Tracy G
