Split mode internal combustion engine with improved NO.sub.x reduction means

A split mode internal combustion engine comprising:

• a first group of cylinders;
• a second group of cylinders;
• an intake system including first and second intake chambers which are respectively connected to said first and second groups cylinders for providing said cylinders with air-fuel mixture, and a valve means for providing a communication between said first and second intake chambers when said engine is in high load condition, and breaking said communication when said engine is in light load condition;
• an exhaust system having first and second exhaust chambers which are respectively connected to said first and second groups of cylinders for separately receiving therein the exhaust gas emitted from said cylinders, said first and second exhaust chambers being united at their downstream portions;
• means for controlling said first and second groups of cylinders in such a manner that when said engine is in the high load condition, all of said first and second groups of cylinders operate to produce power, but when said engine is in the light load condition, only said first group of cylinders operate to produce power;
• first exhaust gas recirculation means for feeding the exhaust gas contained in either one of said first and second exhaust chambers into said first intake chamber when said engine is in the high load condition, and feeding the exhaust gas gathering in said second exhaust chamber into said first intake chamber when said engine is in the light load condition;
• and
• second exhaust gas recirculation means for feeding the exhaust gas gathering in the said second exhaust chamber into said second intake chamber only when said engine is in the light load condition.