A modified equation for the heat transfer coefficient has been established, because the original equation proposed by the author in 1967 provides at low load and motored operation to low results. The reason for this descrepancy seems to be a steady state soot layer, the thickness of which increases with increasing load, where as it does not exist in a motored engine. All equations for the heat transfer coefficient known either to, do not represent the real heat transfer coefficient accuring at the soot layer surface, but include the thermal conductivity resistance of the soot layer. The real heat transfer coefficient is more than two times higher than assumed up to now. These results also show the adiabatic engine in a totally new light.