Reducing pollutant emissions, particularly soot particles emitted by internal combustion engines, is a major challenge for car manufacturers. In this paper, the experimental setup is a turbocharged three-cylinders gasoline direct injection engine installed on a HORIBA dynamic test driven by a HORIBA STARS computer. The particle-measuring device is a Pegasor Particles Sensor that measures the current carried by previously electrically charged particles. The hot engine stabilized tests, with lambda parameter lower or equal to one, have very low emission levels, unlike dynamic tests. As a consequence, the present paper deals with experiments in transient conditions. Unlike diesel engine, cycle tests show that particulate emissions vary widely. To understand the phenomenon, a simple transient was created and reproduced a hundred times in order to obtain enough data to analyze and compare these different tests. This transient starts from idle to reach the speed of 2000 r/min and 60 N.m in 5 s. To reach this point, it is necessary to stay in full load for about 3 s. The maximum deviations of particles reaches 85% with the standard deviation σ=18%. The cylinder pressure sensor shows significant variations at the very beginning of each transient, i.e., during the first 500 ms. This kind of result was observed for Worldwide harmonized Light vehicles Test Cycles (WLTC) with a maximum deviations of particles reaching 75% with σ=30%, on Real Drive Emissions Cycle (RDE) with a maximum deviations of particles reaching 45% with σ=22% and for a 300 s Mini-Cycle with a maximum deviations of particles reaching 70% with σ=17%. The Mini-cycle is made up of the five largest accelerations of the WLTP cycle. A complete analysis highlights the importance of filling the first engine cycles. This depends on the opening speed of the throttle, the position of the crankshaft at the beginning of the transient, and the acceleration of the first cycles. But, the NOx sensor shows very slight variations between each test. As a consequence, it appears that the variation of particles emissions is not only related to variation of equivalence ratio but with another setting, which may be the oil consumption. Finally, from these results, it is possible to determine a particle characterization function. It consists of two functions. The first one is the average of the emitted particles level which depends on the engine speed, engine acceleration, engine torque and torque acceleration. The second function, which corresponds to dynamic variations in emissions, mainly depends on oil consumption in the cylinder and on the combustion quality of the first transient engine cycles.