Embodiments of supercharged internal combustion engines employing improved induction systems for providing better performance at idle low speeds and upon acceleration. A simplified bypass and pressure relief system is incorporated in each embodiment for permitting the engine to induct air directly and independently of the supercharger at low speeds and on acceleration from low speed. A pressure relief valve is also incorporated for relieving excess pressure from the supercharger back to the bypass in the event of excessive supercharger pressures. The system also embodies a fuel injection device that has the pressure of fuel injection controlled in relation to the pressure in the intake passage into which it discharges. Furthermore, an auxiliary induction system is provided for inducing turbulence in the intake charge at low engine speeds to improve efficiency under these conditions.