Downpipe Guide for Cars – Catted Vs Catless?

in a previous blog post, we talk about catalytic converters; what they are, how they work, and why it’s important to keep them in good condition. Related to the subject of catalytic converters, today we are putting our focus on downpipes and especially looking at the differences between catted and catless downpipes. Let’s start with the basics.

What is a Downpipe?

The downpipe is a part of your car. exhaust system🇧🇷 Its main function is to connect the cylinder head and the catalytic converter, channeling the exhaust gases into the converter before they reach the end of the exhaust system. Unless you’ve given the performance of your car’s turbocharger a lot of thought, it’s unlikely that you’ve considered the pipe responsible for moving spent exhaust smoke through the system to the catalytic converter. As long as it works, you might not mind.

The downpipe is the main conduit through which exhaust fumes from the turbine housing reach the vehicle’s exhaust system. Inside the downpipe there is usually a restrictive catalytic converter, which, as you probably know, is responsible for cleaning the exhaust gases of hazardous substances that make fumes incredibly dangerous for human respiratory health.

In fact, downpipes are a hot topic of conversation among those looking to modify their cars and increase vehicle performance. When a car is equipped with a turbocharger, for example, a change in the downpipe can actually increase airflow and thus improve performance. many cars with turbochargers end up being constrained by the bad nature of their own exhaust pipe curvature. Changing the downpipe can change all of that.

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Catted vs. downpipe catless

Generally speaking, people talk about downpipes as being of two types, “with cat” or “without cat”. But what do these terms mean? What is the difference between these two styles of downpipe? First of all, this is a term you’ll really only find in the world of aftermarket auto parts. OEM downpipes are always connected to catalytic converters because that’s the standard they must follow.

Catted downpipes are equipped with a high-flow catalytic converter, which cleans gases in the same way as your OEM catalytic converter. A catless downpipe is one that is not equipped with a catalytic converter. In the absence of the converter, the exhaust gases suddenly acquire a rather unpleasant odor. This is because those nasty fumes that attack the breath are not being cleaned as they should be. On the other hand, the airflow is excellent and the car’s performance will certainly be improved.

drain pipe without cat

What is the downside of standard downpipes?

As mentioned above, a standard downpipe is equipped with a restrictive catalytic converter. While they’re obviously critical to keeping our air clean and breathable, they’re not the high-performance car’s friend when you want it to run. It can be quite disappointing to shell out tens of thousands of dollars only to discover that the car you’re driving is limited in performance by the capabilities of its downpipe and catalytic converter. This is the main drawback in your standard downpipe.

What benefits do aftermarket downpipes bring?

Aftermarket downpipes allow you to improve the airflow of the stock downpipe because they remove the restrictive aspect. These aftermarket alternatives are often made with a larger bore, which creates more room for the exhaust fumes to flow and more room for the turbo to spin. That extra space might seem like a small change, but it’s exactly what your turbo needs to operate with less lag and generate more spool.

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In other words, an aftermarket downpipe allows you to enjoy your car’s performance features much closer to the way it was designed to enjoy them when they were designed. By preventing all exhaust gases from colliding with each other and creating turbulence, you generate a much more balanced and capable system. The following are the types of replacement downpipes that you may find available to you:

  • Single tube with flange design
  • split bell mouth
  • normal bell mouth
  • Divorced Wastegate
  • cast shots
  • pipe formed

catted discharge pipe

What is the benefit of using a Catless downpipe? Is there a downside?

The catless downpipe benefit is essentially an updated version of what we’ve already described above. It almost completely eliminates the back pressure problem and allows incredibly fast turbocharger rotation.

As you can imagine, however, all is not smooth sailing when it comes to catless downpipes. A series of question marks hang over them that should give you pause for thought.

First is the odor. We touched on this above when comparing downpipes with and without a cat. The fact is that without the process of removing harmful gases and other harmful substances found in exhaust fumes, they become quite pungent. On the track, this isn’t much of an issue as there aren’t many people around to smell them. However, this takes us partially to the next issue.

Second is legality. There is a very clear reason why authorities have required catalytic converters for so many years. While they increase the amount of CO2 a car produces, they more directly reduce toxic substances that can cause immediate health problems for human populations. In some US locations, if you are caught with an unplugged pipe, you could face fines of up to $2,750 and your car could be impounded.

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Finally, there’s overboosting. One more problem that exists for catless downpipes is overboost, also known as boost creep. In short, there is an accumulation of air inside the turbine housing of the turbocharger. When this happens, the boost capacity also increases, which may sound great at first, but inevitably leads to overloading the OEM’s fuel system. This can ultimately have dire consequences for your car.

Conclusion: How about a sports cat?

Is the compromise solution to these cat versus no cat questions simply getting a sporting cat? More formally, they are high flux catalytic converters, which can offer the best of both worlds. They reduce energy loss, increase efficiency and keep your car street legal and free of harmful odors and fumes.

If you’re looking at aftermarket downpipes then this is the type we recommend as the best solution to get the highest potential performance but without crossing any weird legal boundaries.

drain pipe without cat

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