In {HEAD ~ an engine} structured to introduce fresh air and an EGR gas into a cylinder, the EGR gas is introduced into the cylinder at least at {TAIL ~ a part} of a compression stroke using a pressure in a combustion chamber at least at a part of a power stroke 
In { HEAD ~ an engine } structured to introduce fresh air and an EGR gas into a cylinder , the EGR gas is introduced into the cylinder at least at { TAIL ~ a part } of a compression stroke using a pressure in a combustion chamber at least at a part of a power stroke
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH