The present work has been focused on the development of low-throughput semi-empirical models to predict the peak firing pressure, indicated mean effective pressure and brake mean effective pressure in direct injection diesel engines. The models have been calibrated and assessed on a 1.6L GM Euro 6 diesel engine, on the basis of the results of experimental tests conducted at a dynamic test bench at GMPT-E (General Motors Powertrain-Europe). Model validation was carried out over "New European Driving Cycle" and "Worldwide Harmonized Light vehicle Test Procedure" missions. The performance of the semi-empirical models has been compared, in terms of prediction accuracy, robustness, inversion efficiency and computational expense, with that of a previously developed real-time physical combustion model. The thus developed semi-empirical models are characterized by a very low computational effort, and are therefore suitable for the development of innovative feed-forward control algorithms in the Engine Control Unit. (C) 2016 Elsevier Ltd. All rights reserved.