Three catalysts such as Cu-X, Cu-Ni-X, and Cu-Fe-X based on X-Zeolite have been developed by exchanging its Na+ with copper, Iron and Nickel metal ions and tested in a commercial Maruti 800 cc S I engine and some encouraging results for reduction of NOx and CO have been obtained. The bi-metal catalysts are named based on the order of ion-exchange treatment. Out of three catalysts, Cu-X catalyst exhibits the best NOx and CO conversion performance while Cu-Ni-X shows better performance compared to Cu-Fe-X catalysts at any catalyst temperature. Maximum NOx and CO conversion efficiencies achieved with Cu-X catalyst are 62.2% and 62.4%, with Cu-Ni-X catalyst are 47.0% and 50.0%, and with Cu-Fe-X are 43.1% and 43.8% respectively.Unlike noble metals, the doped X-Zeolite catalysts studied here, exhibit significant NOx reduction for a wide range of A/F ratio and exhibit a slow rate of decrease with increase in A/F ratio. Back pressure developed across the catalyst bed is found to be well within the acceptable limits and power loss due to the back pressure is only 0.2%. During 30 hours of testing of each catalyst, no significant deactivation of any catalyst was observed.