<div class="htmlview paragraph">The NOx emission of the TOYOTA LEAN BURN ENGINE is lower than that of a conventional engine due to the presence of a prechamber called a “Turbulence Generating Pot”.</div> <div class="htmlview paragraph">The mechanism of this NOx reduction was analyzed experimentally and theoretically.</div> <div class="htmlview paragraph">The results showed that large-scale mixing motions of burned gases were caused in the post flame region as a result of the jet flow from the prechamber. It was concluded that the reduction of NOx emission was due to the decrease of temperature gradient and lowered mean temperature of burned gases caused by these motions.</div>