The intake manifold channels the air needed for combustion into the cylinder head intake ports. The air enters from a central point, a carburetor, or on fuel injected engines a throttle body, and then travels through individual passages called runners to the cylinder head(s). Depending on the vehicle model, the intake manifold can be mounted either on top of the engine between the cylinder banks, or at the side of the engine, attached to the cylinder head.

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On carbureted engines and fuel injected engines with Throttle Body Injection (TBI, also called single point injection), the intake air mixes with fuel as it enters the intake manifold. On multiport fuel injected engines, fuel is introduced to the intake air stream by individual fuel injectors located at the ends of the intake manifold runners. Newer engines with Gasoline Direct Injection (GDI) inject fuel right into the combustion chambers, so the intake manifold delivers only clean air to the cylinders on these engines. Cast iron or aluminum used to be the materials of choice for intake manifolds, but today most manifolds are made of plastic (technically a composite blend). Plastic is much lighter, so it helps in the quest for greater fuel efficiency, and it dissipates heat better than metal, so the intake air charge stays cooler for better combustion.

Many intake manifolds have an upper and lower half. The two halves and the intake manifold to cylinder head(s) junction are sealed with gaskets and secured with bolts. The carburetor or throttle body are attached to the intake manifold in the same manner. The integrity of the seal at these junctures is critical and all surfaces must be clean and smooth when new gaskets are installed to prevent air leaks that could cause a lean air/fuel mixture, rough idle, and poor performance. On many V engine designs the intake manifold also serves as the valley pan, and the ends of the manifold are sealed to the cylinder block. Care must be used here when gaskets are installed or oil leaks could result.

Some intake manifolds have coolant passages and incorporate the mount for the thermostat. On older V engines with carburetors or TBI, an exhaust crossover passage was cast into the intake manifold to heat the manifold and improve fuel vaporization when the engine is cold. Modern fuel injected engines are computer controlled and the computer depends on inputs from many sensors to regulate engine operation. An Engine Coolant Temperature (ECT) sensor may be mounted in an intake manifold coolant passage to provide a coolant temperature signal to the computer, and the air temperature in the intake manifold may be signaled to the computer by an Air Charge Temperature (ACT) sensor mounted in an intake manifold runner.

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  • Replacement Air Intake Parts
    Why Does My Car Have a Plastic Intake Manifold?
    An intake manifold is an integrated assembly that sits atop the engine, consisting of a series of tubes which distribute fresh outside air to each and every cylinder. On V-shaped engine blocks, an intake manifold typically sits between the two cylinder banks while inline engines may feature a manifold to the side of the cylinder head. Intake manifolds serve as a mounting point for carburetors, throttle body assemblies, fuel injectors, thermostats, and more depending on vehicle manufacturer engineering preferences. Intake manifolds may also serve to route coolant through dedicated channels in order to remove heat from the engine. Because of their location and functionality, intake manifold assemblies are under constant stress from engine vacuum pressure as well as direct heat from coolant, cylinder combustion gasses, and the cylinder heads to which they are mounted.

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Intake Manifolds & Components Reviews

Average rating:  4.5  4.7 - 18 reviews
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Lincoln Town Car / Ford Crown Victoria
Our limo company as Town cars in its fleet. We have purchased Dorman® 615-175 - Upper Intake Manifold for one of our vehicles and it worked out 100%. The quality of this item has proven to be extremely reliable. We have purchased from CARiD this particular product before and never had any issues with the unit or their service. In one of our Town cars we put 185.000 miles with Dorman® 615-175 - Upper Intake Manifold and we don't see any issues, so far so good. We currently have 3 Dormans in our vehicles. This is the only manifold that would go into our cars when needed. Hope our experience will help you with your decision. Thank you CARiD. Chariot limousine service.
TPosted by Tomer (North Hollywood, CA) /
2005 Lincoln Town Car
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