This paper presents an experimental investigation of the underhood thermal behaviors during vehicle thermal soak (when the vehicle stops after a large thermal load) by temperature measurement and separate measurements of convective and radiative heat fluxes. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France. The underhood is instrumented by almost 120 surface and air thermocouples and 20 fluxmeters. Measurements are performed for three thermal functioning conditions, with the engine in operation and the front wheels positioned on the test facility with power-absorption controlled rollers. It was found that in thermal soak the temperature of certain components can increase by almost 80°C (pre-catalyst screen) and that of air zones by almost 40°C (crawl area).

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