If you know anything about car exhaust system parts, then you might be familiar with downpipes. If not; read on to learn about what a downpipe is, what it does, why it’s such a vital aspect of your exhaust system, types of downpipes and the pros and cons of upgrading yours.

WHAT IS A DOWNPIPE AND WHY YOU NEED ONE?

Downpipes are sections of tubing that connect the exhaust side of a turbocharger with the start of the vehicle’s exhaust system, allowing used exhaust gas to exit the engine. It is responsible for moving the exhaust gases through the system as efficiently as possible. The downpipe steers gases away from the turbine, creating more uninterrupted power.

The average downpipe has at least one restrictive catalytic converter (CAT). These do an excellent job of cleaning exhaust gases as they are produced. With its position immediately after the turbo, the efficiency of a downpipe directly impacts turbo spool and performance.

Factory downpipes are meant to meet emissions standards and provide enough air movement to meet a stock vehicle’s performance requirements. Aftermarket downpipes are bigger and wider than stock. This means exhaust gases can flow much easier and spool the turbo even harder – creating more energy for the turbo to suck more air and deliver it to the combustion chamber.

WHY YOU WOULD WANT TO UPGRADE YOUR DOWN PIPE?

The stock (original) downpipe flows efficiently enough to handle a Stage 1 software upgrade and basic bolt-on hardware like an intake system. After this, the most beneficial upgrade on a turbocharged vehicle is a high-flow downpipe paired with Stage 2 software. This software upgrade provides significant gains in power and torque. If you install a downpipe on a vehicle and don’t have the proper software you will get a check engine light for this reason and you won’t see any performance gain.

A higher flowing downpipe will need this upgraded software to take full advantage of the higher flow rates. Without a tune, an upgraded downpipe provides moderate gains that are not worth the price. With a software upgrade, up to 75 kilowatts and torque (nm) can be seen on smaller engines and larger engines can see up to 112 kilowatt and over 26 newton-meter of torque over stock. (These numbers depend on fuel grade and other modifications/variables).

TYPES OF DOWN PIPES

If you want to get yourself an aftermarket downpipe, you’re going to run into two kinds: catted and catless. Catted means that it comes with a high-flow catalytic converter. Catless downpipes come without one.

 

– Advantages of catted downpipes:

A catted downpipe provides a significantly higher rate of flow over stock hardware, but retains catalytic converters, protecting the environment.

 

Catless downpipes are definitely not worth it. They are indeed cheaper and can provide a little more horsepower. However, the disadvantages far outweigh the advantages:

– Advantages of a cat-less downpipe:

An advantage of a cat-less downpipe is unrestricted exhaust flow. With no cat, the downpipe is a straight tube allowing exhaust gasses to exit the turbo at the highest possible rate.

– Disadvantages of a cat-less downpipe:

The most obvious disadvantage is the environmental impact of unrestricted exhaust flow. There is also the terrible exhaust smell, failed emissions and a switched-on check engine light.

 

In effect, the difference in power gain between a catted and catless downpipe is small. The best option for both performance gain and environmental impact will be a downpipe with high flow catalytic converters.

Downpipe Types
Decat downpipe

Catalytic Converters (CAT)

How a Catalytic Converter (CAT) Works

Catalytic converters change harmful emissions into harmless gas, and they need to be replaced only if they become clogged or otherwise damaged and can’t function properly. If it has begun to flow poorly due to being clogged up, it will cause the vehicle to run extremely poorly. The vehicle will lack power and fuel economy. In extreme cases, the CAT could overheat and cause components on the undercarriage to combust, melt, or catch fire. A damaged CAT should trigger a Check Engine light.

 

CATS are expensive to replace, so they aren’t considered a regular maintenance item. Due to the cost involved, replacing your CAT should be considered a last resort. If your CAT needs replacement but you don’t have the type of money to replace it there is an alternative option.

 

Mini CATS are the cheapest form of trying to duplicate the efficacy of the CAT once it’s been removed. Often, when removing a CAT, the vehicle’s engine management system will register that the CAT has been removed and it will then place the vehicle into limp mode. The MINI CAT is made with a stainless-steel foil insert that can resist high temperatures. These high-temperature inserts are what creates the same high flow and volume over the sensor to replicate a fully operational CAT.

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Catalytic converter
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To understand whether a downpipe is worth it or not, it’s important to know the pros and cons of a downpipe. (We only discuss the pros and cons of a catted downpipe)

– Pros of aftermarket downpipe:

Increased horsepower.

Louder exhaust sound. Aftermarket downpipe is wider and less restrictive than a stock downpipe. This means sound waves can travel better – providing a louder sound when you accelerate.

Works well with other mods. Stock downpipe can be the most restrictive component in your car. Replacing it today will work well in the future when you decide to also change your exhaust pipe and air intake. Combined together they will provide a much better exhaust flow overall. Take it for tune after you have all these parts – performance gain will be off the chart!

Relatively cheap mod.

No Check Engine Light (CEL) if tuned. If you take your car for a tune after installing a downpipe, then it should not light up the CEL.

 

– Cons Of Aftermarket Downpipe:

Have a slightly unpleasant exhaust smell. With downpipe installed, you may have some unpleasant exhaust smell – likely caused by the less restrictive catalytic converter. You should not be able to smell it from inside the car. 

IS IT WORTH IT TO INSTALL A DOWNPIPE?

·         For horsepower: If you are installing a downpipe for the horsepower gain, then it’s definitely worth it. Combined with a tune, you could see a major boost in horsepower

 

·         For the sound: If you want to install a downpipe just for the sake of an improved sound, then it’s not worth it. We recommend you look into other mods if all you look for is an improved sound. Performance mufflers or axle-back exhaust are good starting points. They both cost much cheaper and will produce better noise.

 

·         Without a tune: Installing downpipe without a tune is not recommended and not worth it. You will not gain as much horsepower as when tuned and you could potentially have wear and tear damages on your exhaust valve.

IN CONCLUSION

Upgraded downpipes provide great increases in horsepower and torque on turbocharged vehicles by allowing exhaust gasses to flow easier as they leave the turbo. Paired with the appropriate software, a downpipe can provide significant gains and make a vehicle more fun and engaging to drive. Keeping the potential downsides in mind, upgrading to a higher flowing downpipe is a great option for those who want more out of their car without moving into Stage 3/upgraded turbo territory.

 

Ready to upgrade your downpipe? VAG Spec Centre has you covered! Our service advisors will help you find the right downpipe and software for your Volkswagen, Audi or SEAT.