Patent ID: 8661787

Claim:
A method of preventing a false-fail in a marine oxygen storage capacity measuring system monitoring a marine three-way catalyst treating internal combustion engine exhaust by oxidizing HC and CO and reducing NO x , comprising; cooling said catalyst with a liquid coolant; providing a first oxygen sensor sensing oxygen in said exhaust upstream of said catalyst prior to treatment by said catalyst; providing a second oxygen sensor sensing oxygen in said exhaust downstream of said catalyst after treatment by said catalyst; performing closed-loop control of said system with said catalyst and said first and second oxygen sensors so as to maintain a fuel-air ratio of said exhaust; during said closed-loop control, initiating open loop control and measuring oxygen storage capacity of said catalyst as a measure of operating efficiency of said catalyst by performing a first step comprising a reducing step adjusting fuel-air ratio Phi to a rich mixture with normalized Phi>1 to reduce stored oxygen in said catalyst, with said first and second oxygen sensors registering respective rich Phi readings, performing a second step comprising an oxidizing step adjusting fuel-air ratio Phi to a lean mixture with normalized Phi<1 to increase stored oxygen in said catalyst, with said first and second oxygen sensors registering respective lean Phi readings, repeating said first and second steps over a plurality of cycles; and preventing a false-fail of said monitoring during the first of said cycles comprising providing an initial lean kick excursion of Phi prior to the first step of said first cycle and terminating at the beginning of said first step of said first cycle such that during said first step of said first cycle said second oxygen sensor registers a richer Phi reading than without said lean kick excursion.