In order to comply with the existing emission norms of BSIII in India or EURO III and beyond that also, it is not sufficient to use the catalytic converter technology alone over the wide range of engine operating maps. Different studies across the world have proved that the cost, drivability, operating range against AFR, heat dissipation rate characteristics of catalytic converter limit their use in startup and idling conditions. One common way to tackle this condition is to use the Secondary Air Injection (SAI) system. In this system, small amount of air is injected after the exhaust port to initiate the thermal oxidation of gases. The right amount of air injected at the right time and at right location will reduce the emission by 37-90%.
In the following study, SI engine vehicle with single cylinder, 160 cc and having carburetor is used as a test vehicle to evaluate the performance of SAI. The SAI system is modeled in AVL BOOST software and validated against the experimental data. The experimental data is collected at transient condition of IDC (Indian Driving Cycle). SAI system of the same vehicle is modified for different parameters like reed stopper height, SAI outlet pipe length and angle of secondary air injection. In order to avoid the complexity in experiments, DOE technique is used. The optimum parameters of SAI are determined for maximum CO conversion efficiency with uncoated CAT. The combination giving best conversion efficiency is then tested with coated CAT for emission cycle. Model results and the experimental results are compared on the basis of mass flow rate.