Abstract: An induction system for an internal combustion engine that improves performance, particularly at low speeds, through the use of a relatively small auxiliary induction system, through which a substantial portion of the low speed charge requirements of the engine are supplied. In accordance with this invention, a cold starting enrichment device in the form of a fuel injection nozzle is provided in a main passage of the auxiliary induction system. In accordance with one feature, a throttle valve is provided in an induction passage and has a smaller cross-sectional area than the passage in its idle position, so as to permit the idle air flow around the periphery of the throttle valve. In accordance with another feature, a temperature responsive air by-pass is provided for flowing additional air into the auxiliary induction passage during cold running, so as to improve warm-up time.

Abstract: An induction system for an internal combustion engine having main induction passages and relatively small cross-sectional area auxiliary induction passages for delivering a charge from a carburetor to the combustion chambers. A control valve arrangement is provided so that the engine charge requirement at idle and low load are supplied through the small auxiliary induction passages so as to increase turbulence in the combustion chamber at the time of combustion. The inlet to the auxiliary induction passage is disposed in the path of fuel discharge from the idle circuit of the associate carburetor so as to improve mixture distribution and promote smooth running. The inlet for the auxiliary induction passage is also positioned at a higher point than the control valve so as to reduce the likelihood of liquid fuel being drawn into the auxiliary induction system. The inlet for the auxiliary system is also heated to improve vaporization.