Do it yourself
Frequently asked questions about cars and motorcycles
Car tutorial (Do it yourself) Motorcycle tutorial (Do it yourself) Frequently Asked Questions

What is the Downpipe catalyst and its legal issues

Model: (Various brands) Various
Part: Diesel particulate filter

Video tutorial

The downpipe (literally "descending pipe") is the first section of the exhaust pipe that connects the exhaust manifold (attached to the engine) to the rest of the exhaust system that runs under the car. It is located from the engine height to under the car, and in many modern cars the original downpipe contains both the DPF filter and the catalytic converter.

The idea is to replace it with a sporty one, which can be of two types: free-flowing (which we will not even consider) and with a sporty catalytic converter, therefore with a high-performance catalytic converter usually with 200 cells instead of the 400/600 of an original one. It is a great compromise because it improves the gas flow but maintains a certain back pressure, useful at low revs.

It has greater efficiency, the engine breathes better and the DPF has less chance of clogging. In the video, the solution of the 200-cell downpipe is recommended but we must still remember that it is a solution on the edge of legality, and that it carries concrete risks (fines, seizure, problems in inspection and with insurance in case of an accident).


Posted on 5 October 2025 by ScegliAuto


Related tutorials

What can be the main causes of the engine warning light being on
What can be the main causes of the engine warning light being on
(Various brands) Various The video illustrates some very common causes: the first is the exhaust system in general. So the lambda probe or faulty oxygen sensor, the inefficie…
How to Check a Catalytic Converter
How to Check a Catalytic Converter
(Various brands) Various What are the signs of a faulty catalytic converter? Firstly, the engine usually stalls shortly after starting, there is poor acceleration, and strang…
The Crucial Function of the Two Lambda Sensors
The Crucial Function of the Two Lambda Sensors
(Various brands) Various If your vehicle experiences hesitation during acceleration, the issue may be due to the lambda sensor, located on the exhaust before the catalyst, wh…

How to open the bonnet on a Volkswagen Golf?

In this tutorial, you will see how to open the bonnet on a Volkswagen Golf MK4. This is a very simple operation that follows the standard procedure. First, open the driver's door, then locate the lever in the lower left area and pull it. Next, move to the front of the vehicle, lift the bonnet slightly, and find the second lever located just above the Volkswagen logo. At this point, simply pull it towards you, fully open the bonnet, and secure it with the prop rod. To close it, gently push it down.

Watch the video!


by ScegliAuto

More videos