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What are Catted Downpipes and What do they do?

The job description of factory downpipes is to clean the exhaust gases from the combustion chamber. But it does so in a restrictive manner. It does a great job cleaning but is also very restrictive causing potential power to be lost. 

If you replace it with an aftermarket downpipe, you are now allowing the turbo to more efficiently move gases away from the turbine to create more power.

An aftermarket downpipe ensures better airflow and less restrictions, resulting in a smoother engine, more horsepower and perhaps the loudest sound possible! However, it is important to choose a downpipe that fits exactly to your vehicle. 

Before anything else, you should know that there are two types of downpipes: catted downpipes which have a high-flow catalytic converter and the catless downpipe which doesn’t have a catalytic converter.

More about Catted Downpipes

A catalytic converter’s job is to clean the exhaust gases as they pass through the catalyst. This means you will not have to worry about the smell of raw exhaust fumes. 

With the increased boost, you’ll have even more exhaust gasses fighting to get out. Even with a completely stock engine, the factory downpipe is restrictive and will rob you of horsepower. 

Replacing it with high flow converter will result in more horsepower over the factory catalytic converter, allowing your boosted car to breathe a lot better. Since the turbocharger is essentially a pump, it is important the pipes entering and exiting the turbocharger are free from restriction. The stock downpipe usually has many bends which creates pressure within the system. By reducing the amount of restriction, the turbocharger can spool up more quickly. A faster spool-up time will increase efficiency in power and fuel economy.

But, are catted downpipes legal?

In states with emissions testing, you will want to install a larger diameter, catted downpipe. Catted downpipes include a high-flow catalytic converter that flows better than stock while keeping your emissions in check. 

Not only do these pipes keep the raw fuel smell to a minimum, but the converter can also act as a muffler, taming your exhaust if you live in a quiet area. This will allow you to pick up most of the gains of an off-road downpipe, while still keeping your performance car emissions compliant. 

In states with California emissions standards, aftermarket catted downpipes may not be legal. You will need to check with your local testing agency before ordering your downpipe if you need a downpipe that is California compliant. Even if you do not live in an emissions restrictive state, a catted downpipe is perfect for highly boosted car owners who do not want the increased exhaust volume and fuel smell associated with a catless downpipe.

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