A transient, one-dimensional spray shear layer ignition model has been formulated to provide a methodology for predicting the autoignition period in direct-injection, quiescent chamber diesel engines. This approach focuses on including the influence of key injection and thermodynamic parameters that affect this key diesel combustion phenomenon. In particular, these important parameters include injection rare, mean spray angle, bulk in-cylinder instantaneous temperature and pressure, and residual gas fraction from a thermodynamic point-of-view. The proposed shear layer model agreed fairly well with experimental autoignition data derived from indirectly measured engine bulk fuel burning rate profiles even though ignition is modeled only according to a one-step Arrhenius-type reaction that accounts for both local shear layer equivalence ratio and temperature. In particular, the proposed model exhibited improved predictive capability in comparison to published zero-dimensional diesel engine autoignition correlations that are typically employed in bulk parameter, diesel engine performance simulation models. (C) 2000 by The Combustion Institute.