At Eurosport Tuning, we offer down pipes for Audi, VW, and Volvo vehicles, so we wanted to go over some of the science of downpipes to help our customers understand what they are and why they're so beneficial.
If you’re ready to unleash more power in your turbocharged VW or Audi, then it’s time to invest in a downpipe. These upgrades are a significant source of power in turbocharged vehicles. It’s worth investing in a downpipe for its increased peak horsepower as it alters your driving experience and takes it to the next level. Here's what you need to know.
First, What's a Downpipe, and How Does It Work?
On a turbocharged vehicle, a downpipe is a part of the exhaust system that connects the turbo exit to the catalytic converter. If the shape and flow rate of this section of tubing can be improved, the turbo will become a little more potent, as it will spool up faster and extract a little more power out of the exhaust at max RPM.
Sometimes, after-market downpipes improve performance because they simplify the path and increase the gas flow rate over the stock unit. They also have a different size and shape than the stock downpipe, sometimes resulting in a performance gain.
The best reason to buy a downpipe is that the performance gain is noticeable at a wide range of RPMs. While it's generally accepted that installing a downpipe will add "just" 10 to 20 horsepower, that gain is noticeable anytime the turbo is engaged. It adds up to a big increase in performance.
Catted vs. Catless Down Pipes
There are two main types of downpipes available to upgrade your vehicle, the catted downpipe and the catless downpipe. Each provides distinct differences, depending on what the driver is looking to achieve.
- Can increase horsepower, assuming they replace a stock downpipe and catalytic with an all in one unit, only the gain isn't as substantial as advertised, as modern catalytic converters aren't terribly restrictive
- Emissions-compliant: If strict emissions laws exist in your state, this is the way to go to meet emissions requirements yet still achieve a significant flow
- Most affordable and readily available design
- If you add a catless pipe and remove the stock catalytic converter, you'll note a distinct gasoline odor emits from the exhaust
- Considerably louder than stock, which is a positive or negative depending on your preference
Different styles of downpipes yield different results. The greater the separation between the gas in the wastegate and the exhaust, the smoother the overall exhaust flow is, due to combustion.
Blank Plate Downpipe Facts:
- Standard component found in stock construction
- Wastegate is fully covered
- Very Inexpensive
Bell Shape Downpipe Facts:
- Open, bell-shaped pipe
- Collects all of the gas from the turbo together and flows into the exhaust
- Universal, fits on most vehicles
- Compatible with most aftermarket turbochargers
Split Bellmouth Downpipe Facts:
- A bell-shape with a divider to separate the exhaust headed to the wastegate from the main exhaust stream
- In some applications, a split bellmouth design makes sense
Divorced/Dual Design Downpipe Facts:
- The downpipe separates the exhaust stream to debatable effect
- Dual compartments separate the exhaust gas from the turbo and the exhaust form the wastegate. Due to the separation, the gases aren’t combined immediately- leading to smoother exhaust flow
Key Differences When Shopping For Downpipes
While you don't always have the option of spec'ing out the perfect downpipe for your vehicle (usually, the downpipe manufacturer does that for you), it doesn't hurt to go over some of the attributes you'll encounter.
- The measurement of the diameters vary.
- Sizes generally range from 2.5, 3.0 and 3.5 inches, with 300-400 HP and greater applications requiring the 3.0 and 3.5 sizes
- Varies, most are stock length, while some are longer
- Donut or flat flange, depending on the type of bolts used
While not well understood by the general public, downpipes are an important performance add-on for most turbocharged vehicles. Be sure to consider them carefully when you're looking for bolt-on performance.