Exhaust emissions are significant pollutants that affect urban lifestyles. There are several regulations related to the exhaust emissions of both gasoline and diesel engines. In this study, the effects of a controlled heating of the exhaust line before the catalytic converter on the converter efficiency are experimentally investigated. Experiments were conducted based on either discrete or cold start conditions. For discrete conditions, the engine was operated until it reached normal and steady state operating conditions. Then, the engine was stopped until the catalytic converter surface temperature reached the ambient temperature. The experiments were first started without additional heating and then continued with different heating loads. In the second stage, the catalytic converter behavior and conversion efficiency under cold start conditions were investigated. The exhaust gas after the exhaust manifold was preheated with different heating loads for the first 150 seconds after the start of the engine; however, the exhaust line was heated 15 s before starting the engine. The effects of the location, length and heat loads of the electrical resistances on the catalytic converter behavior were investigated. After all of the experiments, it was concluded that with the appropriate location and heating loads, for discrete operating conditions, the hydrocarbon (HC) and carbon monoxide (CO) emission conversion efficiencies reached nearly 100 % after 50 s of starting the engine. For cold start conditions, the hydrocarbon (HC) and carbon monoxide (CO) emission conversion efficiencies reached 35 % and 80 %, respectively.