What’s Better Catted or Catless Downpipe?

Catted Downpipe

There are a few things to consider when deciding whether or not to get your downpipe catted or catless. Before we go into the differences, let’s first define what the difference is between ‘catted’ and ‘catless’. A catalytic converter is a device that reduces air pollution by converting hydrocarbons, carbon monoxide and NOx into water vapor, carbon dioxide and heat through a chemical reaction with oxygen present in the exhaust gas.

A Catted Downpipe has a catalytic converter installed within it while a Catless Downpipe does not have one attached. The acronym for cats can be broken down as follows: Catalytic Converter (C), Air (A) To (T) Ylic (A) Bull (T). A Catted Downpipe always means there is one installed.

First of all, if you are thinking about getting catless downpipes, make sure your car is compatible for it. Check to see if your vehicle has a catalytic converter in the exhaust system or not. This can be done by removing the metal pipe leading into the main exhaust tunnel and looking inside of it where the catalytic convertor should be located . If your vehicle does have a catalytic converter in the exhaust system, then you will need an aftermarket tuner to remove it before replacing downpipe or else you will cause major damage to your car’s engine. For example, all B7 Audi A4s (2005-08.5) and all 2008.5+ A5/S5 models do not require a tuner for catless downpipe installation. However, older model B6 A4s (2004-2007) will need an aftermarket tuner to remove their catalytic converter before installing a catless downpipe .

The next thing to consider is what you plan on doing with your car and how often you plan on modifying it in the future. If you plan on keeping your car stock or making minor modifications i.e. intakes and chip tuning, then we recommend getting a catted downpipe as opposed to acatless one. This is because of two major reasons: Catalytic Converter is made of precious metals such as palladium and platinum. For this reason, when a catalytic converter ends up in landfills, it ends up being considered hazardous waste because of the pollutants it can release into the environment . By getting a catted downpipe, you are participating in conserving these materials which helps in protecting our environment.

Catalytic Converters help reduce overall vehicle emissions. Depending on what state you live in, certain vehicle models tend to have higher emission regulations. Although there aren’t any specific regulations for aftermarket catless downpipe usage, if you plan on living in a state with strict emission regulations , having a catalyzed downpipe will bode well for you.

Lastly, if you are thinking about installing catless downpipe, you should know that this is one of the most common modifications to cause a check engine light in your car. So if you plan on keeping your car in good condition and without any issues i.e. less likely to give into temptation of modifying it in future , then we recommend sticking with catted downpipe which will not cause problems when the time comes when want to return back to stock or when funding runs low for modification.

However, if its already too late for changes, don’t worry because there are plenty of tuning companies out there making custom tunes for catless downpipes so that they meet emission standards . This way even if your car throws a check engine light, you can always return and get your car reflashed for a small fee.

But if you want to stay legal and keep your warranty intact, we recommend running catted downpipe with Stage 2 software such as APR instead of catless . Or better yet wait until your car is paid off and trade in towards an Audi A5 or S5 which will come stock with catted downpipe from factory.

Catted Vs. Catless Downpipe (Comparison)

Catted Downpipe

– Prevents check engine light problems if you plan on keeping your car stock or don’t want to modify it in the future.

– Retains warranty for cars bought brand new and still covered under Audi/VW manufacturer’s warranty .

– Helps reduce overall emissions for states with strict emission regulations.

Catless Downpipes (Not Recommended)

– Illegal in some US states. *Check state laws before making purchase*

– Will cause issues with emissions test if you live in a state where emissions testing is done often i.e., yearly emissions inspection every 2 years, etc… Check states where tailpipe testing is required on annual basis .  And keep in mind even if your state doesn’t require emissions, there are many testing stations that will still pull you over for inspection. This is why we recommend getting a tune with catless downpipe because it will not cause problems during emissions testing or when trying to get car inspected.

– Won’t be covered under Audi/VW manufacturer’s warranty in case anything goes wrong after installation (burned up catalytic converter, failed emissions test, causing check engine light). Even though custom tunes can help cars pass emissions tests even when installed catless downpipes, the bad outweighs the good when you consider all of the risks involved .

My Recommendation

If you are unsure if catless downpipe will cause problems with the check engine light, please contact your local dealer to inquire about your car’s warranty coverage. We recommend waiting until the warranty has expired before making modifications so that if anything goes wrong, you won’t have to pay for expensive repairs at a dealership. For those of you who already have catted downpipe installed on their cars and want to upgrade to an even more powerful tune, there are plenty of custom tuners out there making tunes specifically designed for aftermarket downpipes which brings us back around full circle in showing how incredibly rewarding it can be in expanding capabilities and performance of this iconic German luxury car.

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