The problem with stock boost tubes is simple: they’re full of restrictions. Small diameter tubing, tight bends, and abrupt transitions all cost airflow and air density before that charge reaches the intake manifold. Our Banks Boost Tube Upgrade Kit fixes that by using the largest tubing we can physically route through the engine bay, larger-radius bends, and smoother tangential coupler transitions. On the 2017-2019 Duramax, moving from 2.5-inch stock tubing to 3.5-inch tubing increased mass airflow 26% on the hot side and 45% on the cold side. That means better boost retention and better throttle response, because the turbo doesn’t have to work as hard to make the same boost.
The video explains that the factory Duramax boost tubes contain multiple airflow restrictions. The tubing itself is restrictive, the bends create additional restriction, and changes in tube diameter further disrupt airflow. Together, these features make it harder for charge air to move efficiently through the system.
Banks addresses these limitations with three primary design strategies. First, it uses the largest tube diameter that can physically fit through the engine bay. For most Banks boost-tube applications, that maximum practical diameter is 3.5 inches.
Second, the tubes use the largest bend radii possible to avoid forcing airflow through tight turns. Third, where the tubing must transition between different diameters, Banks uses tangentially curved transitions rather than abrupt steps. These transitions are shaped similarly to a rocket nozzle to maintain smoother airflow through the charge-air system.
Using the 2017 through 2019 Duramax as an example, Banks increased boost-tube diameter from the stock 2.5 inches to 3.5 inches.
The larger cross-sectional area, combined with smoother bends and transitions, reduces restriction and increases the system's airflow capacity.
Banks reports measurable improvements on both sides of the charge-air system.
On the hot side, which carries compressed air from the turbocharger to the intercooler, the Banks boost tube increased mass airflow by 26%.
On the cold side, which carries air from the intercooler to the intake manifold, mass airflow increased by 45%.
According to Banks, reducing restriction through the boost tubes allows the turbocharger to achieve the required airflow and boost with less effort.
The result is improved charge-air delivery and quicker throttle response. Rather than forcing the turbocharger to overcome unnecessary restrictions in the factory tubing, the larger and smoother Banks boost tubes provide a more efficient path from the turbocharger through the intercooler and into the engine.
