Development of the Ultra Low Heat Capacity and Highly Insulating (ULOC) Exhaust Manifold for ULEV 980937

With the total amount of air pollution caused by vehicle emissions on the increase, the problem has now became a global concern, and various regulatory measures have been put into effect in each region of the world. This is especially true in California, U.S.A, where countermeasures have been adopted early. There, the ULEV (Ultra Low Emission Vehicle) standard, which was ones deemed impossible for gasoline engines to meet, is now in effect. In response to these developments, Honda announced the ULEV system for a 2.2 liter gasoline engine with a closed-coupled catalytic converter (CC) and an under-floor catalytic converter (UF) at the beginning of 1995, and reported on the system's emission characteristics. ¹⁾

A new ULEV system has been developed based on the previous system but using only UF, aiming for marketable improvements in product characteristics such as higher output. The new system features the ultra low heat capacity and high heat insulating (ULOC) exhaust manifold. The ULOC has less heat loss, resulting in a higher exhaust gas temperature flowing into the UF when starting the engine at cold temperatures, and a reduction in the required catalyst activation time. The newly developed exhaust manifold and exhaust pipe has ultra low heat capacity and high insulation characteristics because of a hollow double structure with an inner tube that has a thickness of 0.6mm. Optimization of the configuration and assembly method of each part allows for the exhaust manifold excellent durability and high output.