Combustion process in a quiescent chamber diesel engine is modelled using a multizone model. This model divides the cylinder charge into two zones, namely the unburnt zone (surrounding air) and the burnt zone (fuel spray with entrained air). The burnt zone is subdivided into 16 concentric sprays, instead of only eight sprays as in previous work, each one with its own temperature and composition. Liquid fuel, fuel vapour, air and products of combustion are assumed to be present in each zone. Real gas relations are used to calculate the properties of the mixture while products of combustion are assumed to be in chemical equilibrium at local temperature. The extended Zeldovich mechanism is used to predict the NO x formation. The cylinder pressure, temperature, heat release rate, NO x rate and concentration are calculated. For different injection pressures, injection advance angles and different fuel orifice hole diameters, the results show that the model can predict the measured cylinder pressure with high accuracy but it predicts the measured heat release rate and NO x emission rate with moderate accuracy. In addition, the effect of injection parameters on the NO x emission and engine power is predicted and it has been shown that NO x emission can be reduced without noticeable loss of engine power. This can be done by appropriate choice of injection pressure, injection advance angle and fuel nozzle hole diameters. A cw heat transfer surface area (m 2 ) A ori orifice area (m 2 ) d inj nozzle diameter (m) D cw cylinder bore (m) C d discharge coefficient C pi specific heat of each combustion species (kJ=kg K) f m jet centre-line concentration (kg=m 3 ) h f specific enthalpy of fuel (kJ=kg) h u specific enthalpy of unburnt mixture (kJ=kg) H cw heat convection coefficient (kJ=m 2 ) i inj number of holes in injector L length scale (m) m ae air entrainment mass (kg) m b mass of burnt fuel (kg) m f rate of injected fuel (kg=s) m spray mass of instantaneous spray fuel (kg) m sur mass of instantaneous surrounding air (kg) m u mass of unburnt fuel (kg) n engine speed (r=min) NuNusselt number P pressure (Pa) q w heat transfer rate (kJ=m 2 ) Q f heat absorbed during heating and evaporation (kJ) Q rel released heat during combustion (kJ) r v compression ratio r 0 initial droplet radius (m) R j jet radius (m) s stroke (m) S penetration (m) t time (s) T a surrounding air temperature (K) T ign ignition temperature (K) T m mean charge temperature (K) T spray temperature of instantaneous spray (K) 427 The MS was