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Methanol lean burn system based on Toyota's new concept four valve engine has been developed. The power unit is a new 4 valve 1.6L in-line four with compact combustion chambers. Lean misfire limit was extended by using a swirl control valve that improves combustion under partial load. An EGR system was adopted to reduce NOx emissions and an under-floor type catalyst was also used to reduce formaldehyde emission in the cold transient mode in addition to the manifold type catalyst. 0.4 g/mile NOx and about 11% better fuel economy than stoichiometric feed back operation under FTP driving cycle were obtained. Driveability of the vehicle still remains to be improved. Although low formaldehyde emission was obtained at low mileage using this system, further study on the stabilization of the aldehyde emission level during mileage accumulation is necessary.