The present work aims to analyze a torch ignition system running on lean homogeneous charge, adapted to an Otto cycle multi-cylinder engine. The main objective is to maximize engine efficiency by means of redesigning the ignition system adapting a pre-chamber to the main combustion chamber. This new ignition system allows reducing its IMEP covariance for leaner mixture operation due to the increase of ignition energy availability during the kernel formation. The engine used in this research is a commercial sixteen valve, four cylinders in line with cubic capacity of 1600 cm3. The performance date of baseline engine operating stoichiometrically were used as a reference for the comparison with torch ignition engine output running from stoichiometric mixture to its leaner operational limit. The brake mean effective pressure was maintained constant in all test configurations in order to make possible to compare engines thermal efficiency. The torch ignition system allows faster flame propagation demanding and consequently less ignition advance for the very same operational condition. This phenomenon is a result of much higher turbulence reducing the probability to face knock. Then, the use of leaner mixture in this system became a powerful tool to allow increasing brake efficiency and making possible to recover its power density by means of turbocharger and the increase of the compression ratio for instance. In this way, the torch ignition system becomes an interesting option for highly efficient and less pollutant SI engine.