Intake Manifold: Description and Operation

DESCRIPTION











The intake system is made up of an upper and lower intake manifold. The upper intake manifold is made of a composite for the 3.3L engine (Fig. 119) and aluminum for the 3.8L engine (Fig. 120). The lower intake manifold is common between the two engines (Fig. 121). It also provides coolant crossover between cylinder heads and houses the coolant thermostat (Fig. 121).
The intake manifold utilizes a compact design with very low restriction and outstanding flow balance. This design allows the engine to perform with a wide torque curve while increasing higher rpm horsepower.
The composite upper intake for the 3.3L engine has a unique cover over the upper portion of the manifold (Fig. 119). This cover is designed to absorb intake noises and also offers styling to the engine. This cover, under any circumstance, should never be removed. The fasteners attaching the upper intake manifold can be accessed without removing this cover. If, for some reason, the molded-in vacuum ports break, the composite manifold can salvaged. The vacuum ports are designed to break at the shoulder, if overloaded. Additional material in the shoulder area provides sufficient stock to repair. Also, if the special screws that attach the MAP sensor, power steering reservoir, throttle cable bracket, and the EGR tube become stripped, an oversized screw is available to repair the stripped-out condition.

OPERATION
The intake manifold delivers air to the combustion chambers. This air allows the fuel delivered by the fuel injectors to ignite when the spark plug fire.