Unclog the clog: Killing a Duramax Pt 12

We just picked up 60 horsepower by unclogging the clog in the pipes. Sometimes you hit a design wall, and no matter what tricks you try, no matter what tuning tricks you do, you’ve either met or exceeded the design limitations of a part.

0:00 – Intro
3:08 – 912 horsepower
6:58 – Exhaust system backpressure
12:10 – Turbocharger Boost to Backpressure Ratio
17:22 – Engine Scavenge Ratio

Not a single component of the mighty Duramax L5P in the Banks video series “Killing a Duramax” has yet to succumb to the riggers of what Gale and the crew have thrown at it. We swapped out parts for higher-performing components, such as upgraded fuel components and the turbocharger.

A new high-flowing turbo from Precision 76/75 helps the engine reach 852 horsepower and gets the exhaust to spin. The stock turbine inlet piping, pedestal, and turbine outlet are effectively choking the turbo’s assembly. These parts not only cause an exhaust restriction but also elevate exhaust pumping restrictions and add heat. That’s where the unclogging comes into play.

To get the turbo working more efficiently, the exhaust system needs an enema! To remedy this and get the turbo spinning to its full potential engineers have removed and replaced the stock 2.25” manifold outlet pipes with 3” and replaced the stock pedestal with a fabricated high-flow collector. This new turbine inlet flow combined with a 5” turbine outlet unclogged the clog, and without any other changes, Gale and the crew hammered the throttle getting 912 hp, proving that you can make sizable horsepower increases with the proper piping. 

We did all of this to find power where most people don’t think to look. All we had to do was unclog the pipes. Next up, a new Comp Cam should help this engine hit 1,000 horsepower.