Stratified burn internal combustion engine

In an internal combustion piston engine, the improvement comprising, in combination:

• walls forming a combustion chamber having first and second intake valve ports and at least one exhaust valve port, a first intake valve for controlling flow through the first intake valve port, a second intake valve for controlling flow through the second intake valve port, an exhaust valve for controlling flow through the exhaust valve port, a spark plug communicating with said combustion chamber, means including a first intake passage for supplying a relatively rich air-fuel mixture to said first intake valve port, means including a second intake passage for supplying a relatively lean air-fuel mixture to said second intake valve port, a first throttle valve in said first intake passage, a second throttle valve in said second intake passge, a first and a second air valve that operate at a minus load of said engine and which introduce by said first air valve a relatively small amount of air into said first intake passage and by said second air valve a relatively large amount of air into said second intake passage, means for controlling operation of said first and second throttle valves so that during an intake stroke of the engine the air weight introduced into the combustion chamber through the first intake valve port is less than the air weight introduced into the combustion chamber through the second intake valve port, and so that the following relationship exists at least in the range of low loads of the engine:
• A.sub.TH.sbsb.1 /A.sub.V.sbsb.1 <A.sub.TH.sbsb.2 /A.sub.V.sbsb.2
• where
• A.sub.TH.sbsb.1 :
• effective opening area of said first throttle valve at each load.
• A.sub.TH.sbsb.2 :
• effective opening area of said second throttle valve at each load.
• A.sub.V.sbsb.1 :
• effective sectional area of said first intake valve port.
• A.sub.V.sbsb.2 :
• effective sectional area of said second intake valve port.