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Cycle resolved fuel droplet dynamics measurements in the inlet port of an S.I. engine were performed under firing conditions in order to study real dynamic effects in the fuel flow to the engine. A Phase Doppler Particle Analyzer (PDPA) was used to detect the droplet size and velocity. The optical access was through a glass window in the bottom of the intake channel. The PDPA was synchronised with the engine combustion cycle in order to study the results in the engine frequency domain. The measurements were performed over the cross section of the channel. Different injection timing and engine running conditions were investigated, using standard unleaded gasoline. The results show that, during the camshaft's overlap period, there exists a “push-back” droplets effect, due to the pressure difference between the inlet manifold and the cylinder, that transports droplets far back in the inlet manifold.