What is a Decat?

Just as humans need to breathe in and out to survive, vehicles also require a similar mechanism to function better. We use this point as an introduction: Given the stringent emissions standards, automotive companies are obligated to conduct rigorous and unusual tests on vehicles to meet these standards, adding and removing components and mechanisms. This has resulted in vehicles not breathing properly, or in our analogy, their inhalation and exhalation being disrupted! The responsibility for disrupting the breathing of gasoline engines lies with the catalyst, while for diesel engines, it is managed by the DPF, EGR, and AdBlue! However, our discussion here focuses on catalysts. So the question is:

How have catalytic converters caused cars to breathe improperly?!

A catalytic converter and its baffles can become blocked, obstructing the exit of gases from the vehicle. This leads to back pressure and slower throttle response, all of which directly affects the car's power. In fact, these factors cause the Reynolds number of the fluid, or the exhaust gases, to increase, resulting in the flow of these gases becoming turbulent or chaotic instead of uniform.

What does "decat" mean?

"Decat," or "delete catalyst," refers to the removal of the catalytic converter from the vehicle. Individuals who undertake this action either have a blocked catalyst or one that is close to being blocked! Essentially, they want to resolve this issue through decat and also experience more power and acceleration. But how is this done?

Decat Exhaust:

After decat or removing the catalytic converter, you need a replacement, which is natural. The decat exhaust is one of these replacements.

In fact, the decat exhaust is a straight pipe that helps facilitate the smooth and efficient flow of gases and actually enhances the speed of this process. However, these "increases" do not always lead to "improvements"!

When using the decat exhaust or, in fact, the straight pipes, the back pressure significantly decreases, and some of the volume of returning air is reduced. This causes the turbo to draw in more air into the engine, which is not what we want because in this case, aside from the overboost, we will have a large volume of air and little fuel, which translates to a lean AFR (air-fuel ratio) that over time can lead to overheating and damage to the engine. (So you see how back pressure can be both good and bad!). But it is precisely here that ECU tuning techniques come to our aid! In such cases, depending on the type of vehicle, its ECU, and engine, it is necessary to make adjustments in certain tables such as "Lambda Request", "EGT," or even "Air intake" to resolve the issue.

Is a decat exhaust a stage 2 remap?

If you want to replace the decat with a decat exhaust and have a straight pipe, it is essentially a stage 2 remap because you need to adjust several parameters, such as those mentioned above, specifically and with awareness of the specifications of the new straight pipe (diameter and material) to experience more horsepower without issues or error codes.

However, a decat can be a stage 1 tuning or, in fact, a single-parameter remap; this is possible with lambda O2 removal.

Lambda O2 removal or P0420 delete:

If you want to perform decating without physically removing the catalytic converter, you actually need lambda O2 removal (which is somewhat different from decating; at least in terms of naming). This is usually done by deleting the P0420 DTC through software. In this method, after the software deletion, the process is completed by manually disconnecting the second oxygen sensor. Essentially, this removes the data from the second oxygen sensor from the ECU circuit and helps prevent a drop in engine power to some extent.

You should note that in some cases, this does not resolve issues like back pressure (as this is a mechanical problem, not a software one). This is where it is better to consider options like exhaust ducting.

Decat and Stock Cat: Advantages and Disadvantages:

Apart from saving on the high costs of repairing and replacing a faulty CatCon, reducing vibrations and unpleasant odors inside the vehicle cabin, as well as improving initial acceleration and throttle response, are among the advantages of a decat. However, stock cats also have their benefits; the vehicle noise is lower, air pollution will be reduced, and as a result, your child may blame you less in the future for the melting polar ice and climate change! Keep in mind that the useful life of catalytic converter is between 50,000 to 70,000 kilometers, so if you are approaching this number, make a decision as soon as possible.

 

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