Evaluating Effects of Exhaust Heat Recovery Systems on Fuel Economy and Emissions

The exhaust heat recovery system (EHRS) in an automobile captures the thermal energy from exhaust and transfers it to the engine coolant. As the car warms up, engine friction is reduced and transmission efficiency increases. Certain vehicles with idle speed bump, transmission oil heaters, and cold-temperature fuel enrichment will have enhanced impact of a faster warm-up. Therefore, the impact of the EHRS is very specific to a vehicle and must be evaluated separately. A method was developed to evaluate the effect of an EHRS on a 1.2-L, naturally aspirated, gasoline engine passenger car typical in India.