When you lift up the hood of your vehicle, and look down into the life of the vehicle, you may feel like you have entered a world of confusing complexity. But there is no need to panic as we are going to examine one (of many) under-the-hood saviors called the manifold. So, what is the manifold and what does it do?
In the automobile world, the manifold is an important part of your engine. The manifold is like the cop that directs and manages the flow of essential gases inside and outside of your vehicle.
Because automotive technology changes and improves, manifold design also changes and improves. Many recent engines use variable intake manifolds which can change the length of the intake runners to improve airflow at different engine RPMs. This results in increased torque and power across the RPM range.
What is Engine Manifold?
Manifolds are separate pipes connected to the cylinder head that provide the air-fuel mixture and exhaust gases, which are called manifolds, they are usually made of cast iron, so that it can withstand the high temperature of exhaust gases.
Types of Manifolds in Engine
Following are the two types of manifolds used in vehicles:
- Intake Manifold
- Exhaust Manifold
#1. Intake Manifold.
The intake manifold is the cast iron or aluminum tube for the air-fuel mixture from the carburetor to the engine intake port.
Unless the superchargers or governors are utilized, the intake manifold, when attached to the carburetor, allows the mixture to have all cylinders.
Constructional Details with Parts:
The carburetor is mounted on the intake manifold. The intake manifold has mounted one side of the cylinder block on L-head engines, and on the side of the cylinder head on I-head engines. It is located between the two cylinder banks on V-8 engines.
A good design of intake manifold has the path from the carburetor to the cylinders as short and smooth as possible so that no condensation forms and collect on the walls of the manifold.
To reduce condensation and to help vaporize the gasoline in the mixture, the modern intake manifold is heated.
Working Principle
Heat is typically supplied from the exhaust gases or cooling water, and sometimes hot spots are added at the point where the fuel hits in the intake manifold.
The heat supplied is regulated by a thermostat so that all of the exhaust gases are diverted to heat the intake manifold when the engine is cold until it warms up, and less heat enters the manifold as the engine gets warmer.
A single passage manifold connects the carburetor directly to the cylinder. In a four-cylinder engine, for example, there are four passages from each cylinder that submerge in a single passage to connect to the carburetor.
To ensure good distribution of the air-fuel mixture, it is preferable to keep the distance of each of the cylinders from the carburetor about the same.
Typically, if a dual carburetor is used, a dual intake manifold will be supplied, with two branches, one for each barrel of the carburetor.
Branch feeds will be supplied to half of the engine cylinders, which keeps from strokes of each of the barrels overlapping and improving uniformity of distribution.
In the case of a four-barrel intake manifold, the primary barrel leading outlets on the same side of the carburetor feed the same cylinders 2, 3, 5, and 8, while the left side feeds cylinders 1, 4, 6, and 7.
#2. Exhaust Manifold.
The exhaust manifold is a pipe to carry the exhaust gases away from the engine cylinders. The exhaust gases are collected from the exhaust ports of all engine cylinders, and routed to a single exhaust outlet.
Constructional Details and Parts
The exhaust manifold is generally made of cast iron. On L-head engines, it is fastened to the side of the cylinder block, while, on I-head engine, it is bolted to the side of the cylinder head. V-8 engines employ two exhaust manifolds, one on each bank of cylinders.
Each manifold may be connected to either a separate exhaust pipe, muffler, and tailpipe, or they may be connected to a crossover pipe that routes exhaust through a common muffler and tailpipe. Fig illustrates an exhaust manifold for an eight-cylinder, in-line passenger car engine.
Working Principle
The design of exhaust manifolds, as much as possible, prevents exhaust strokes from overlapping to keep backpressure to a minimum.
This is usually accomplished by structuring the exhaust manifold in two or more branches, so that two cylinders will not discharge their emissions into the same branch simultaneously.
The design includes large radius bends to eliminate restriction of flow. The exhaust also runs over a heat tube to supply heat to the automatic choke unit built into the carburetor.
The center section of the exhaust manifold is actually connected to the intake manifold of an in-line engine using a heat trap and exhaust damper unless the intake manifold is water heated.
The exhaust damper is controlled by a thermostat that deflects exhaust gases away from the intake manifold. When the engine is cold, all exhaust gases pass around the intake manifold.
Common Engine Manifold Problems
Over time, the engine manifolds develop failures that could result in catastrophic engine and/or other component failures. Below are some failures which you should address:
Cracked or broken Manifold
With continued exposure to extreme temperatures, the material expands and contracts which leads to cracks in the manifold. If your engine has a poor-quality manifold, or if the manifold engine component has been in service for too long, it can develop cracks in the manifold.
These cracks can cause loud noise and degrade your engine performance. Additionally, failing to fix the crack on time will cause more catastrophic problems to your engine, such as engine misfires and damage to other engine components.
Exhaust Manifold Leak
Loose or broken bolts, rust, or gaskets can break the bond between the manifold and engine head. This causes an exhaust leak which results in extremely loud noises almost like a cracked manifold material.
Exhaust Manifold leaks will cause your engine performance to degrade and use more fuel. Further it will cause damage to your engine and other components.
Carbon Buildup in the Intake Manifold
Over time, the accumulation of carbon deposits will develop inside the manifold, especially in vehicles that utilize direct injection fuel systems.
This can result in incomplete combustion and poor fuel quality that can cause the engine to work harder during the combustion process. This means it will lead to sluggish acceleration as well as decreased performance.
Vacuum Leaks in the Intake Manifold
Vacuum leaks in the intake manifold occur because unmetered air enters the engine. This affects the amount of air to fuel the mixture that is needed during the combustion process.
Vacuum leaks can occur because of a bad gasket, loose vacuum hoses, or cracks in the manifold itself. Vacuum leaks can cause an increase in strain on the engine and decrease fuel efficiency as well as overall engine performance.
Warped Manifold
Heat cycles cause the material used for the manifold to warp Super hot then super cold will alter its shape and this can lead to an improper seal between the manifold and the engine block.
Also, the result is exhaust leaks, low energy power, and further unfair fuel efficiency.
Signs Of Engine Manifold Problems
Because engine manifold problems can cause critical damage to the engine system and its parts, it is important to learn to identify them and how to treat them. Here are signs you can pay attention to, for effectively identifying manifold problems earlier:
- A rough idle or backfire might be a sign of an intake manifold issue.
- Exhaust manifold could have crack/leak if you can hear loud noise.
- A poor emissions test could be a sign of a failing exhaust manifold.
- Reduced fuel efficiency could indicate a failing intake manifold.
Maintenance Of Engine Manifold
Correctly maintaining the engine manifold is very important for the operations and performance of the vehicle. You can effectively maintain the engine manifold by taking the following steps-
- Complete regular inspections of engine manifolds for signs of wear, leaks, or cracks.
- Clean debris/dirt from the manifold regularly to increase its lifespan.
- Look at the intake manifold and gasket, replacing or repairing as required.
- Consider installing a catch can to lessen the amount of dirt/debris buildup.