There are six different types of downpipe exhaust systems, and it is important to know which one is the best for you. A Volkswagen mk7 GTI will use a different type of downpipe than a Subaru WRX.
- Flange with simple pipe
- Bellmouth
- Split bellmouth
- Divorce wastegate
- Cast outlets
- Formed piping
Flange with simple pipe
This type has a major advantage due to its simple design and relatively cheap cost. It is easy to form, and the pipe requires little manual work. It is one of the main reasons why factories prioritize this type.
Bellmouth
Like the previous type, the Bellmouth is easy to manufacture and packages easily. It lacks complexity, and therefore the risk of failure is minimal. Car enthusiasts favor the Bellmouth the most, giving the biggest performance improvement.
Split Bellmouth
This option is split because it separates the gasses in the beginning and joins them together at the rear of the bell mouth section. There are various advantages to such a system, including the reduced cost and simplicity. Keeping things simple will always get you the best results.
Divorced Wastegate
To combine several advantages, the gasses are kept away from the turbo outlet until they reach the end of the system. When they are combined in the back, the process is more efficient. There is also a significant pollution reduction.
Cast outlets
This design allows for the heat to be kept in the exhaust. It is also easy to design, and you can make it in any shape you want. The disadvantage is represented by increased weight and cost.
These pieces will have a significant weight which will negatively affect the performance. Some manufacturers will sell this piece at an increased cost because the casting forms are very expensive and can be quite complex.
Formed Piping
This part shares the same freedom in design with the casting, but it is also cheaper and lighter. The manufacturer has to be precise with the building process as improper forming will negatively affect the flow. If this part has a poor design, then the flow will struggle regardless of the quality of the entire system.
A catalytic converter is good for the environment and will prevent this problem from happening. The diameter of the pipe has a small effect on the flow rate, but it is not an important factor. If your vehicle has 300 horsepower, a pipe 2.5 inches in diameter will be just enough.
3 inches are recommended for faster vehicles that can deliver 600 horsepower. Beyond this point, several restrictions come into place.
Catted
The catted downpipe is better for you if you are driving on the street with a daily driver. While they provide 10 less horsepower than a catless ones, they feature more advantages. It includes fewer emissions and the absence of a specific unpleasant smell.
Catted downpipes are installed with a catalytic converter that cleans the gases. However, you won’t find this part in a catless downpipe where the fumes gain an unpleasant odor.
Pick a catted downpipe if you have an Audi A3 or a similar vehicle that you drive daily to work. It increases efficiency and reducing emissions. The name of this part implies that it contains a catalytic converter, which is also the most expensive part of your vehicle.
This catalytic converter is often manufactured with precious metals, therefore increasing its price and value. If you need to replace a catted downpipe, you should expect to pay more.
