In one embodiment, a method includes receiving, via a first sensor, a signal representative of at least one of a manifold pressure, a manifold temperature, or a manifold mass flow rate of a manifold. The method further includes deriving, via a manifold model and the first sensor signal, a gas concentration measurement at a first manifold section of the manifold. The method additionally includes applying the gas concentration measurement during operations of an engine, wherein the manifold is fluidly coupled to the engine.