Carburetor circuit for internal combustion engines

In a carburetor circuit for an internal combustion engine, a combination comprising a carburetor having wall means defining an intake manifold having an air inlet end, an opposite discharge end, and a throat portion between said ends, said wall means being formed in the region of said inlet end with an outlet through which fuel is fed during acceleration of said engine;

• a butterfly valve in said intake manifold adjacent said discharge end movable between an open and a closed position;
• fuel feed passages communicating with the interior of said manifold in the region of said butterfly valve for feeding fuel into the manifold during idling of the engine;
• first fuel injection means for injecting fuel into the region of the throat portion into the interior of the manifold during the normal operation of said engine;
• and second fuel injection means for feeding fuel into said manifold during acceleration of the engine and comprising a tube portion tightly inserted into said outlet, a first small diameter tube communicating with said tube portion and having an outlet end in the region of said inlet end of said manifold and a second small diameter tube communicating with said tube portion and having an outlet end closely adjacent said butterfly valve, said second small diameter tube extending through the interior of said manifold.