System protecting exhaust catalyst from overheating in spark ignition engine

摘要

To reduce catalyst (8, 9) temperature below critical levels, the air-fuel mixture is weakened. Exhaust gas is passed through a catalyst (8) without oxygen storage capacity, then through a catalyst (9) constructed as a three-way catalyst. Preferred features: The first catalyst is a wash coat without cerium, which has a palladium and/or platinum content. Both catalysts occupy a common casing.