Using optimized sensors developed with 25 years of grain loss experience, almost any combine harvester can be fitted with a grain loss system. The sieve sensor measures the amount of grain lost from the sieves, thus indicating that adjusments need to be made to the fan speed or to the overall throughput of the machine. For example, the straw walker sensors measure the loss from the straw walkers (the bottleneck of combine throughput) and indicate that the straw walkers canot keep up. In this instance, the operator should slow down. Combining the inputs (loss/no loss) from the sensors fitted at the sieves and the straw walkers can be utilized to increase combine harvester performance. The sensitivity for each sensor can easily be set to allow for different grain sizes.