Exhaust system with three-way catalyst immediately following exhaust manifold and NOx adsorption catalyst connected selectively downstream via static gas-insulated auxiliary line, solves cold starting problems

摘要

A three-way catalyst (16) connects to the exhaust manifold (14) as closely as possible to the engine. An NOx adsorber (24) downstream of the catalyst is separated from it by at least 1.5 m, preferably 2 m or more. The separate internal line (36) has markedly smaller cross section, and is largely insulated by the surrounding gas inside the exhaust pipe (20) between three-way catalyst and NOx adsorber. Preferred Features: The separate line (36) runs inside the central length of exhaust pipe (20) from the front pipe section (18), right up to the NOx adsorber. An exhaust block valve (38) is located near the NOx adsorber. The separate line also extends inside the front pipe (18) to the three-way catalyst. Downstream of the three-way catalyst, a cooler-silencer section (22) is included. Its enlarged peripheral surface area, promotes heat transfer (cooling exhaust gases only when they are hot and flowing in its outer region). The separate line passes through it. The exhaust pipe and separate line comprise two double-walled C-shaped half-pipes which are connected together gas-tight, by longitudinal welded, or brazed connections. In alternative construction, continuous sheet metal is employed. An oval section, with ribs or grooves to increase area, may be used to enhance cooling at the outer periphery.