Exhaust system affecting suction of secondary air by use of larger connector pipe

Claim 1

In an exhaust line of an automotive internal combustion engine, the exhaust line including an exhaust manifold, an exhaust pipe assembly, a catalytic reactor adapted to oxidize hydrocarbons and carbon monoxide contained in the exhaust gas of the engine and capable of transmitting pulsations of the exhaust gas pressure, a front tube as part of the exhaust pipe assembly arranged to pass the exhaust gas from the exhaust manifold to the reactor, a main muffler located downstream of the catalytic reactor, a center tube as part of the exhaust pipe assembly arranged to connect the catalytic reactor to the main muffler and a secondary air supply mechanism for drawing air from the atmosphere into the exhaust line upstream of the catalytic reactor based on the pulsation of the exhaust pressure in the exhaust line, the improvement comprising the front tube having over the entire length thereof an inner cross-sectional area substantially smaller than the inner cross-sectional area of the center tube.