A system for estimating a scavenging ratio of an engine of a vehicle, the scavenging ratio relating to an overlap of opening of intake and exhaust valves of a cylinder of the engine , the system comprising: an intake manifold absolute pressure (MAP) sensor configured to measure a pressure of air in an intake manifold of the engine ; an engine speed (RPM) sensor configured to measure a speed of the engine ; and a controller of the engine , the controller being configured to: retrieve, from a memory of the controller a model surface relating various measurements of the engine speed (RPM) sensor and valve overlap durations to modeled scavenging ratios of the engine ; generate, based on calibration data measured by a calibration system , a calibrated multiplier surface relating various measurements of the intake manifold absolute pressure (MAP) and engine speed (RPM) sensors to calibrated multipliers; determine a modeled scavenging ratio of the engine based on the measured engine speed and a known overlap duration using the model surface ; determine a scavenging ratio multiplier based on the measured intake manifold absolute pressure (MAP) and measured engine speed (RPM) using the calibrated multiplier surface ; determine the scavenging ratio of the engine by multiplying the modeled scavenging ratio by the scavenging ratio multiplier; and control the engine based on the determined scavenging ratio. an intake manifold absolute pressure (MAP) sensor configured to measure a pressure of air in an intake manifold of the engine ; an engine speed (RPM) sensor configured to measure a speed of the engine ; and a controller of the engine , the controller being configured to: retrieve, from a memory of the controller a model surface relating various measurements of the engine speed (RPM) sensor and valve overlap durations to modeled scavenging ratios of the engine ; generate, based on calibration data measured by a calibration system , a calibrated multiplier surface relating various measurements of the intake manifold absolute pressure (MAP) and engine speed (RPM) sensors to calibrated multipliers; determine a modeled scavenging ratio of the engine based on the measured engine speed and a known overlap duration using the model surface ; determine a scavenging ratio multiplier based on the measured intake manifold absolute pressure (MAP) and measured engine speed (RPM) using the calibrated multiplier surface ; determine the scavenging ratio of the engine by multiplying the modeled scavenging ratio by the scavenging ratio multiplier; and control the engine based on the determined scavenging ratio. retrieve, from a memory of the controller a model surface relating various measurements of the engine speed (RPM) sensor and valve overlap durations to modeled scavenging ratios of the engine ; generate, based on calibration data measured by a calibration system , a calibrated multiplier surface relating various measurements of the intake manifold absolute pressure (MAP) and engine speed (RPM) sensors to calibrated multipliers; determine a modeled scavenging ratio of the engine based on the measured engine speed and a known overlap duration using the model surface ; determine a scavenging ratio multiplier based on the measured intake manifold absolute pressure (MAP) and measured engine speed (RPM) using the calibrated multiplier surface ; determine the scavenging ratio of the engine by multiplying the modeled scavenging ratio by the scavenging ratio multiplier; and control the engine based on the determined scavenging ratio. <EOS>