What’s a downpipe
It can be seen from the following figure that Down pipe refers to the section of exhaust pipe that is connected with the middle section or the middle section after the exhaust pipe head section.
A downpipe connects the exhaust manifold to the catalytic converter and directs the exhaust gases out of the turbine housing into the exhaust system.
Why modifiy the downpipe?
Performance, sound and appearance are the three original purposes of exhaust modification, and performance is the main purpose. The downpipe on your turbocharged vehicle is directing the exhaust gases out of the turbine housing into the exhaust system. After modification, the down pipe will improve the performance and sound wave, especially for the turbo car. Because the exhaust gas after driving the turbine to rotate passes through the down pipe at the first time after coming out of the turbine, the smoothness of this section directly affects the working state and working limit of the turbine. The head section of the original factory car is generally designed in a fine way, and contains a high mesh three-way catalyst, so the exhaust gas will stay here for a long time. This will slow down the smoothness of the exhaust, and the second will cause heat accumulation. The former will affect the response speed of the turbine, while the latter will threaten the life of the turbine. Therefore, if you want to increase the horsepower of ordinary turbine cars by a large margin, the Down pipe really has to be changed.
The purpose of upgrading down pipe is to improve performance by increasing traffic. Turbulence is one of the main factors. If gases remain stagnant and/or run into bumps or each other, more back pressure will be generated than a well-designed system. The more laminar flow of gas flow (smooth and straight), the more flow of the system for a given pipe diameter. Steep angles and sudden pipe diameter changes should be avoided.
Type of downpipes
Some common pituitary designs include a flange with a simple pipe, Bellmouth,Spilt Bellmouth, divorced wastegate and so on. Which works best also depends on many different factors and how they are designed and manufactured.
Flange with simple pipe
The only advantages of this design are cost and simplicity. There is no need to form a pipe, and the flange is simple, so the cost is reduced. When the exhaust valve gas converges with the turbine gas at the turbine outlet, it will indeed generate turbulence at the worst position behind the turbine and reduce the flow, so it will not improve performance as other designs do.
Bellmouth
This method is closer to the best way to connect the outlet gas. They have more connection space. If the transition is handled properly, it can flow into the main pipe well. It is well packaged, without too much complexity, thus reducing the point of failure.
Spilt beltmouth
This design separates the gas at the beginning of the turbine outlet and combines the gas at the rear of the bell mouth. It works well, and has some advantages of a bell mouth and a separate exhaust valve design. The main obstacle in this regard is the cost and complexity of adding splitters.
Divorced wastegate
It is an attempt to separate the gas from the turbine outlet and exhaust valve to a further place in the system, combining the advantages of not collecting gas with the real world. It is better to put them far away than to collect them near the exit. In addition, it is also essential to provide power for production and to connect pipes smoothly and avoid turbulence. The disadvantage is that it adds a lot of cost and complexity. The temperature difference on each pipe is large, which will cause the system to break. It is helpful to install flexible joints or expansion joints.
The different down pipe designs are introduced above. We can clearly see that those with catalytic converters, or “cats”, and those without. These are also referred to as catted vs catless downpipes. The above is all the sharing today, see you next time!
Post time: Dec-19-2022