<div class="htmlview paragraph">The dual-throat jet technique has been successfully used to improve cold-starting of the swirl-type IDI diesel engines. It has been proven that, with the aid of the second throat connecting the swirl chamber and the main combustion chamber, the cold-starting process was more stable, quiete and clean. However, the understanding of the mechanism of this technique is far less than satisfied as regarding to the better control and further development.</div> <div class="htmlview paragraph">An intensive fundamental experimental investigation of the transient process of the ignition and combustion at cold-staring had been conducted on a swirl-chamber IDI diesel engine with the help of high-speed photography. Based on the results of this investigation, the following conclusions have been approached: 1) There exist three types of heat release rate pattern at the cold-starting. Different pattern will result in different engine behavior. 2) The secondary throat has double effects on the engine starting characteristics: (a) improvement of the ignition conditions in the main chamber by directly delivering pilot fuel; (b) improvement of the fuel/air mixing process by intensifying turbulence in the swirl chamber, which depends on the geometrical shape and orientation of the throat.</div>