In the context of LEV and ULEV, and to improve performances and passenger comfort, the closed loop optimisation of the engine torque is one of the major element of the engine control strategy. To do that, the knowledge of instantaneous engine torque is needed. In this paper, we are looking for economical and reliable methods to estimate the average indicated torque (of each cylinder) during its combustion stroke based on crankangle measurements. These methods use an engine model which must be both simple for ‘on line’ implementation and accurate enough for a good estimation. We will be presenting and discussing the assumptions and the requirement to meet for this determination.