The influence of ambient temperature on exhaust emissions during cold start in the homologation test

The cold start phase in an ICE is susceptible to changing environmental conditions, especially ambient temperature. The work aimed to analyse the influence of different thermal conditions on the concentration of pollutants and operating parameters of the drive unit during a cold start. The tests were conducted on a chassis dynamometer at various ambient temperatures. The same homologation cycle was used in both cases, allowing direct comparison of results. The concentrations of HC, CH₄, CO₂ and NOx were recorded, as well as the basic operating parameters of the engine: coolant temperature, rotational speed, load and throttle position. Based on empirical data, mathematical models describing the influence of ambient temperature on the dynamics of emissions and stabilisation of engine operation were developed. Relationships were identified that allow for assessing the time to reach steady-state conditions as a function of starting temperature. The results of the analysis provide the basis for developing a start control strategy in climatically variable conditions. They can support the development of adaptive emission control systems compliant with current and future legal standards.