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Intake Manifolds from 1A Auto:
Leaking coolant into the oil: As manufacturers have started using composites and plastic in the manufacture of intake manifolds, they have encountered problems that did not occur with cast iron or aluminum. Most often the problem is a wearing or warping of the coolant passage which allows coolant to enter the engine oil. This has been known to happen on Ford 4.6L V8 engines and high mileage GM 3.8L V6 non-supercharged engines. You can check for this by inspecting your oil when you check it. If your oil appears brown, has tiny bubbles in it, or is foamy, this is evidence there is coolant leaking into the oil.
Cracking: Temperature extremes caused by sub zero weather, engine overheating or a combination of both can cause cracking in newer manifolds, as well as in cast iron and aluminum manifolds. Cracks cause vacuum leaks which result in lost power, low fuel economy and poor low-speed engine response.
Performance increase: Replacing your stock intake manifold with one that offers better performance is a cost effective way to boost the output of your engine. While our current line of intake manifolds are stock replacements, keep your eye out for more performance oriented products in the future.
Some sites will tell you the intake manifold gets the air and fuel from the carburetor or throttle body to the heads. While this is true, it is only a small part of what the intake manifold can do for you. The most important thing that happens in carbureted or throttle body injected engines is that the air and fuel is introduced and the initial mixing process (atomization) begins in the intake manifold.
Ideally you want your fuel to atomize as much as possible before combustion. A properly tuned intake manifold helps this process. Carburetors or throttle body engines introduce the fuel at the top of the intake manifold. They rely on a certain amount of heat and air movement to help atomize the fuel. Throttle body fuel injection differs from carburetion in that the throttle body uses fuel injectors to spray a fine mist of properly metered fuel into the air stream. This fine spray aids in fuel atomization. In most carbureted vehicles a good amount of fuel actually runs through the engine without ever burning because it does not fully mix with the air. Hence the better fuel economy and power advantage of fuel injection.
On port fuel-injected engines (also called Multi-Port or Sequential-Port), the intake manifold only carries air. The fuel is introduced when the air gets close to the intake valve. The fuel injector is located very close to the port (hence the name) and sprays a fine mist. These fine mist aides in fuel atomization. The proximity of the fuel injector to the port eliminates vaporization or overheating of the fuel due to contact with the hot surface in the intake manifold. This allows the vehicle to produce more power with less gas, therefore improving fuel economy. Secondly, with port fuel injection, there is an injector at every port. This allows for very consistent fuel delivery, resulting in better idle, low speed operation, and throttle response, even with more aggressive cams. Sequential port injection is an even further advancement in which the fuel injector spray is in sequence with the opening of the engine intake valve.
Runner Length, or the length of an intake manifold passage from the carburetor or throttle body, has a significant effect on engine torque or "off-the line" power. An intake manifold with longer runners will allow an engine to produce more torque. When your piston is on a down stroke, it creates vacuum and therefore sucks air and fuel from the intake manifold. Engines that have long intake manifold runners can "store" more air/fuel in the runner for the next time the intake valve opens. The longer the runner length the more air is "waiting" to go in to the cylinder as opposed to the cylinder having to "compete" with the other cylinders for the air coming from outside of the carburetor or throttle body.
Intake manifolds are made of one of three different materials. Cast iron intake manifolds are most popular on older vehicles. Because of its low cost, cast iron is still a material used on present day engines although less often. In the 50's and early 60's hot rodders and drag racers started using aluminum. Aluminum offers 2 advantages over cast iron: less weight and better heat transfer properties. Early fuel injected engines such as the one in a rare '57 Pontiac Bonneville actually used sheet steel to form the intake passages. Other early fuel injected engines used modified versions of cast iron or aluminum intake manifolds, such as found in a 1957-63 Corvette. As fuel injection has advanced, manufacturers have become more creative with manifold design. The need is to make the intake passages longer in order to help the engine produce more torque. Chevrolet's Camaro IROC-Z and Corvette, as well as Pontiac's Trans Am, Formula and Firebird used a Tuned Port Injection system in the late '80s and early '90s. This tuned port system utilized an aluminum plenum and throttle body with "tuned" composite runners to funnel the air to the port injectors and into the cylinder heads and intake valves. Modern fuel injected engines now commonly have composite or plastic and aluminum intake manifolds. As manufactures have looked for more torque and horsepower, they have come up with more complicated passages, lengths and routings that result in a manifold that either can not be cast in metal, or would result in far too heavy a manifold.
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