Through analysis and numerical simulation, the late lightoff (similar to3 min) of the current automobile catalytic converter is attributed to a downstream ignition phenomenon that is unstable to flow-rare fluctuations. A design is proposed which incorporates a stable and thermally efficient leading-edge ignition. The key feature involves diverting a small portion of exhaust gas through a bypass stream which contains an electric preheater and a preigniter, during startup. This allows the preheater to utilize a low power input using the existing battery and yet raise the gas temperature beyond a precise minimum that rapidly lights off the entire preigniter. The hot preigniter is then used to light off the main catalytic converter Removal of the bypass after complete ignition presumes the preigniter catalyst, a major advantage. The optimal design is shown to lightoff within 10 s and reduce pollution by almost 90% over current designs and thus meet ultra low emission vehicle (ULEV) standards.