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What symptoms tell us that the exhaust manifold is bad or malfunctioning? Grwa's excellent  research development and production capabilities make it no longer difficult for you when select manifolds!

Views:1008     Author:Site Editor     Publish Time: 2021-09-06      Origin:Site

Automobile engines are always connected with a pile of twisted and bizarre metal pipes. These pipes are divided into multiple pipes, made of cast iron or welded with stainless steel. Their scientific name is exhaust manifold.


Exhaust manifolds are engine components can found on all internal combustion engines. Exhaust manifolds are usually made of cast iron or stamped steel and are designed to collect exhaust gases from engine cylinders and deliver them to the exhaust pipe for exhaust. The exhaust manifold is connected to the engine cylinder head and has ports to collect exhaust gases from each individual engine cylinder. Cast iron manifolds are usually one-piece, while stamped steel manifolds are usually welded together. Both are designed to withstand the high temperature and high pressure required to capture and transport waste gas. Although they are heavy-duty in nature, they are still prone to problems, which may lead to driving performance problems when they have problems. Usually, damage or failure of the exhaust manifold will produce some symptoms to alert the driver to potential problems.

What symptoms need attention?

1. Noisy engine exhaust

One of the first symptoms of engine exhaust manifold problems is excessive exhaust noise. If the exhaust manifold is ruptured, broken or leaking, it may cause the exhaust to leak and make a noisy sound. The vehicle may make a hissing or knocking sound from the engine compartment, which may become louder when the engine accelerates.

2. Reduce power, acceleration and fuel efficiency

Engine performance problems are another symptom that may be caused by a faulty exhaust manifold. If the exhaust manifold breaks or leaks, it will lead to exhaust leakage, which will have a negative impact on engine performance. Exhaust leakage will reduce vehicle power, acceleration and even fuel efficiency.

3. The smell of burning from the engine compartment

Another symptom of exhaust manifold problems is a burning smell from the engine compartment. If there is any problem with the heat shield of the exhaust manifold or the exhaust leaks, the excess heat can damage nearby electrical and plastic components. The exhaust manifold can reach temperatures in excess of 900 degrees Fahrenheit, which can cause any nearby or contacted components to burn out. Burnt parts may produce the smell of burning plastic, sometimes accompanied by smoke, and may cause other problems, so any burning smell should be checked to make sure they are not a major problem.

Why do engine exhaust manifolds have various shapes?

The exhaust gas generated after engine combustion needs to be discharged from the cylinder in time, which needs the help of exhaust system. The exhaust system consists of exhaust manifold, three-way catalytic converter, muffler and exhaust manifold.


One end of the exhaust manifold is connected with the engine cylinder block, and the other end has multiple ports with divergent pipelines to concentrate the exhaust of each cylinder into the exhaust manifold.



Engines with different number of cylinders have exhaust manifolds of different shapes. For example, 4-cylinder engines have manifolds composed of 4 branches. Some engines combine these branches into a main pipe, commonly known as 4 out 1 (or 4-1), while others first combine two and then combine them into one, that is, 4 out 2 out 1 (4-2-1).


Generally speaking, the original engine mostly uses the 4-1 format due to cost considerations. Modified cars prefer to use the latter, because there is an extra pipe, which is beneficial to deal with the problem of exhaust interference of each cylinder and enhance the exhaust effect of the engine.


In the final analysis, there are actually two reasons:

1. Reduce exhaust resistance when exhausting, avoid mutual interference, and exhaust more smoothly.

2. The layout is different according to different models.

On the whole, the issues that need to be considered in the design of the exhaust manifold:

1. Performance; 2. Cost; 3. Vehicle space layout and model compatibility; 4 Cold vehicle emission performance

The performance needs to consider exhaust back pressure, exhaust uniformity between cylinders, and how to reduce exhaust interference from each cylinder. For turbocharged engines, it is also necessary to consider how to balance exhaust back pressure and turbine response. For back pressure, uniformity. The one-dimensional thermodynamic calculation will select the appropriate exhaust manifold pipe diameter, the length of each branch pipe, the pipe diameter of the main pipe, and how the manifolds of each cylinder are connected. For reducing exhaust interference of each cylinder, for example, the usual firing order of 4 cylinder engines is 1342, which will be designed so that cylinders 1-4 and 2-3 will first merge and then merge into the main pipe, effectively reducing the problem of exhaust interference from adjacent firing order cylinders. , Such a manifold is also more complicated; in theory, when each branch of the exhaust manifold is very long, there is basically no problem of mutual influence between each cylinder. At this time, it is also necessary to consider the length of each manifold to ensure that each cylinder exhausts. Uniformity, the very long spatial arrangement of the exhaust manifold, so on all performance models, the exhaust manifold looks very complicated, far more than your example picture.

Regarding cost, the stainless steel exhaust pipe has the best performance, is more free in design, and the structure looks more complicated, but the cost is relatively high. The performance of cast iron exhaust pipes is relatively poor, so the cost is relatively low.

Although exhaust manifolds are usually designed to be heavy-duty to enjoy a long service life, they are still prone to problems because they are often under high pressure conditions. If you suspect that there may be a problem with the exhaust manifold of the vehicle, please ask a professional technician (such as a technician from GRWA) to inspect the vehicle (you can feed the problem video to us, and we will help you troubleshoot the problem) to determine whether the vehicle needs it Replace exhaust manifold.

If you clearly need to replace the manifold, GRWA can help you even more.


We can provide you with products in a variety of styles and materials, and we have drawing capabilities to accept product customization.

Our manifold products have unique tooling positioning in each process of the production process, reducing errors, ensuring that the product is properly loaded, saving installation costs, and improving work efficiency.


GRWA implements a strict quality inspection system, and each set of products will be tested by accurate inspection tools before packaging to ensure that each set of products has no deformation and no installation problems.


The inner wall of the tube is smooth and free of burrs. Ultrasonic cleaning ensures that there is no impurities inside the pipe, the air flow is unobstructed, and the performance is stable.


For stainless steel manifolds, we will use three-pass welding. Argon arc welding can ensure that the product is shock-resistant, firm, and air-tight. Fish-scale welding beautifies the weld of the product, and the pulse can make the product more refined. Three times of welding can ensure that the product is not easy to break in the harsh driving environment and reduce maintenance costs.


For products that require brightness on the surface, we will perform three-layer fine polishing, which will make the surface of the manifold brighter and more beautiful, and make the manifold look very high-end.


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