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What role do three-way catalysts and exhaust manifolds play in the exhaust system

Update:19 Jun 2020

The three-way catalyst is an important part to ensure t […]

The three-way catalyst is an important part to ensure the quality of exhaust gas. It mainly purifies harmful gases such as carbon monoxide, hydrocarbons and nitrogen oxides in engine exhaust gas. And because the three-way catalyst on most cars does not hinder the exhaust flow rate much.

The exhaust manifold is the most expensive part of the modified exhaust system. Because of the strict requirements on length, curvature and caliber, the production cost is very high. Now many newly designed 4-2-1 exhaust manifolds can be improved at the same time. The engine's medium and high speed performance, like most of our racing cars, uses 4-2-1 exhaust manifolds.

If the entire section of the exhaust pipe is replaced with a high-performance model, it will have a lot of help for the horsepower improvement. Because the high-performance exhaust pipe is thicker than the original car, the inner wall is smoother, and the curvature is smaller, these designs can allow a large amount of exhaust gas generated by the engine to rotate at a high speed smoothly, and significantly improve the exhaust efficiency.

However, it should be noted that excessive diameter will affect the back pressure effect and cool the exhaust gas too quickly. In addition to slowing the flow rate, the ground clearance of the exhaust pipe will be reduced, increasing the chance of the car being "bottomed".

In general, if the engine has not been heavily modified, the diameter of the exhaust pipe of a naturally-intake engine with a displacement of less than 2 liters should not exceed 50 mm, and the 2-liter turbo engine should also be within 70-80 mm. There is no need to replace the middle exhaust pipe separately. The middle section is the cheapest part of the exhaust system, but with the addition of a catalytic converter it is different.