Boosted Performance Duramax LLY Downpipe

Duramax LLY Downpipe Upgrade Guide

While the Duramax LLY was an unquestionable improvement over the LB7, it still had a few kinks. One of the main complaints among owners is overheating, which is caused by both a restrictive intake horn and also downpipe. Upgrading the downpipe is one of the best options for preventing overheating and is also one of the best performance upgrades for these engines.

Upgrading the LLY downpipe can help reduce EGTs by a significant amount, improve turbo response, help fuel economy and free up a few trapped horsepower. In this guide we’re going to discuss the important of LLY downpipe upgrades and the performance and reliability benefit they add.

We’ve manufactured an LLY downpipe upgrade via our in-house brand, Boosted Performance, to reduce the restriction from the factory downpipe and to provide awesome performance benefits.

The Issue with the Factory Downpipe

The factory LLY downpipe is not good in any of those regards. In fact, it is one of the main limitations to making big power from the LLY. The factory downpipe is skinny and not optimized for airflow. It is called a “squished downpipe” in the community, as it uses a restrictive tapered, and flattened design that is detrimental to airflow. 

LLY downpipes are very simple components. Unlike some other downpipes that introduce other variables into the equation, like catalytic converters, downpipes are pretty much exactly what they sound like; a bent pipe. Most aftermarket Duramax downpipes are nearly identical in shape, but there is a bit of variation in terms of materials.

Duramax LLY Downpipe Upgrade Benefits

  • Decreased EGTs
  • Increased turbo response
  • Better sound at WOT and idle
  • 5-10whp gain on stock turbo without tune
  • 15-40whp gain with upgraded turbo and tune
  • 1-5 MPG improvement

One of the main reasons that we recommend owners to upgrade their downpipe is the impact that it has on exhaust gas temperatures. The LLY is known to overheat easily when towing or under heavy stress. Aftermarket pipes typically have better thermal properties than the stock unit. This helps reduce EGTs by up to 100 degrees fahrenheit, while also cooling faster after a period of intense heat. This not only keeps your LLY healthier but also helps improve turbo efficiency and response.

In addition to those benefits, it also provides some performance and sound-related perks as well. Due to the fact that the factory LLY downpipe hampers exhaust flow, you’ll see a bit of added performance with a better-optimized downpipe. 

Our Boosted Performance Downpipe

We’ve been manufacturing a downpipe for the LLY for a few years now. There are a lot of options out on the marker but we believe our product offers the best combination of price, quality, and performance. Here are some of the specs and benefits:


Upgrading the downpipe of your Duramax LLY can provide significant benefits and improve the overall performance of your vehicle. The stock LLY downpipe is known for its restrictive design. As a result, it hampers exhaust flow and leads to increased exhaust gas temperatures (EGTs) and decreased turbo efficiency. By installing an upgraded downpipe, you can address these issues and unlock the true potential of your Duramax engine.

One of the primary advantages of an upgraded LLY downpipe is the reduction in EGTs. Diesel engines are particularly sensitive to high EGTs, which can cause damage to the turbocharger. Aftermarket downpipes with better thermal properties can lower EGTs by up to 100 degrees Fahrenheit. That plays a larger role in improving turbo efficiency and response while also ensuring the longevity of your engine.

Additionally, an upgraded downpipe can provide performance gains by optimizing exhaust flow. The factory downpipe restricts airflow, limiting the engine’s power potential. With a freer-flowing downpipe, you can experience improved horsepower, torque, and fuel economy. However, it’s important to note that the performance gains will be more significant when paired with other modifications such as an upgraded turbo and a tune.

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