The heat transfer models proposed in previous studies are not suitable for small-scale spark-ignition engines, because they were developed primarily for large-scale engines. In order to improve the accuracy of the predicted heat transfer rate for small-scale engines, a heat transfer model using the Stanton number is proposed in this paper. Prediction results of instantaneous heat flux, global engine heat transfer, and cylinder pressure based on the proposed model are compared with the experimental results and prediction results of previous models. It is found that the proposed model has prediction results closer to the measured data than the previous models at most engine operating conditions. (c) 2006 Elsevier Ltd. All rights reserved.