This 427 cubic inch supercharged twin-turbo Duramax is built around one problem: a diesel in a monster truck cannot wait for boost. The blower is there to give virtually instant throttle response, while the twin turbos carry the airflow needed for big power. Up front, the engine uses separate belt systems for the blower and accessories so each drive can be sized for its job. We slowed the hydraulic steering pump to help keep it alive, drove the fuel pump in its efficiency range, and packaged the alternator into the system after moving from a two-pump fuel setup to a single 14mm stroker pump. On the air side, four MAF sensors and four Banks Ram-Air Intake System filters give this engine enough measured inlet capacity to support the expected 220 to 250 pounds per minute of airflow needed for roughly 1,400 horsepower. The whole combination is about response, control, and keeping the support systems working at 6,300 to 6,500 rpm.
Gale Banks introduces a highly unusual Duramax build: a 427-cubic-inch, supercharged twin-turbo diesel intended to run to roughly 6,500 rpm before heading to the dyno. The project is being assembled in the Banks Power engine shop and is configured specifically for dyno testing at this stage. Banks begins by explaining the front-drive layout, where the engine is divided into two separate systems: a blower drive and an accessory drive. That separation is central to how the engine achieves both the airflow and the responsiveness required for its intended use.
The blower drive uses an 8 mm pitch, 75 mm wide timing-belt system. It is set up with a 2:1 overdrive ratio, so at 6,300 engine rpm the supercharger turns 12,600 rpm. Banks emphasizes this as a dedicated drive system, separate from the accessories, because the blower is not an add-on convenience item in this engine; it is a core part of the performance strategy. The supercharger is there to provide immediate airflow and instant response, something a turbo-only diesel arrangement cannot deliver on its own.
The accessory drive is also based on an 8 mm pitch belt, but in this case the belt is 30 mm wide. Banks notes that this arrangement is specific to the dyno setup and will differ from the final installation in the truck. The drive path runs from the crankshaft to the hydraulic pump, then to an idler, then to the fuel injection pump, through a belt-tensioning idler, across the Beckmann alternator, over another idler, and back to the crank. He describes the system as giving instant response under acceleration with no slip, which is important when the engine is being tested at high speed and load.
The first accessory being driven is the power steering pump. Banks describes it as a commercial hydraulic pump similar to the units commonly used by monster-truck teams. Those teams often drive such pumps at approximately crankshaft speed from the nose of the crankshaft on large Chevrolet 540-cubic-inch engines, but they also commonly experience pump failures. To avoid that problem, Banks chose to drive this pump somewhat slower. The tradeoff is that if the speed is reduced too much, steering assist may become inadequate.
The pump is mounted out front for two reasons. First, that location provides easy access to the hydraulic inlet and outlet fittings. On the dyno, the pump will operate and circulate fluid into a tank. Second, the pump rotates opposite the crankshaft direction in this arrangement. If it were mounted behind the front engine accessory drive plate, it would turn the wrong way and fail immediately. Banks makes clear that the front placement is therefore not just convenient but necessary for correct pump rotation and durability.
The second driven component is the fuel injection pump, mounted on the back side of the plate. Banks identifies it as a Bosch-based 14 mm stroker pump from S&S Diesel Motorsports. His expectation is that this single pump will support about 1,400 horsepower at a nominal 6,300 to 6,500 rpm. The pump is intentionally driven slightly slower than crankshaft speed so it remains within its efficient operating range.
Banks explains that an earlier version of the setup used two injection pumps. After discussing the combination with Andrew at S&S, he learned that a single 14 mm stroker pump could likely carry the required fuel load. Moving to one pump freed up enough space to add an alternator. The third accessory in the system is therefore a 370-amp Elite Series Beckmann alternator. That packaging change simplified the front-drive arrangement while still supporting the engine's projected power target.
Banks then turns to the intake side, where four large filters are mounted ahead of the turbo system. He notes that these are the same large filters used in a Banks Ram-Air system for the L5P GM pickup. They are being used here because the engine employs four mass-airflow sensors. Each 4-inch MAF sensor uses a 6-inch inlet bellmouth tapering down to 4 inches and can measure approximately 62 to 65 pounds of air per minute.
Based on the expected airflow demand of this engine, Banks predicts the combination will need slightly more than three sensors' worth of capacity and somewhat less than four. To accommodate that, the team built special right-hand and left-hand manifolds feeding the pair of Precision 6870 turbochargers. Drawing on previous dyno experience with this monster-truck engine program, including one earlier engine combination and the destruction of an L5P Duramax on another dyno session, Banks estimates the new setup will require roughly 220 to 250 pounds of air per minute to produce 1,400 horsepower. Since each MAF sensor tops out at about 65 pounds per minute, four sensors provide a total measuring capacity of about 260 pounds per minute, enough to cover the expected range.
Banks places the supercharger in the broader context of the project. This is a monster-truck engine, and in that environment throttle response matters as much as peak airflow. A turbo diesel, even with compounded turbocharging, does not respond instantly when the driver asks for power. The blower is included specifically to solve that problem by delivering virtually immediate boost and airflow.
He ties this strategy to his earlier Pikes Peak work, where he also used a blower-and-turbo combination. In that application, the engine used a 5-liter Whipple supercharger, and Banks notes that the blower on this project is the exact same size as the one used at Pikes Peak. In the earlier system, the turbocharger fed into a very large charge-air system with a huge intercooler mounted in the nose of the Freightliner, and water was sprayed on the air-to-air charge-air cooler to super-chill the intake charge. The lesson carried over here is that the blower is not replacing the turbos; it is there to provide the immediate response that the turbos alone cannot.
The intended operating environment explains many of the engineering choices. Banks says monster-truck drivers perform what he describes as vehicular ballet, requiring abrupt transitions, immediate torque delivery, and precise control. In that kind of use, waiting for turbo speed to build is unacceptable. The supercharger therefore becomes imperative, not optional, because it gives the engine the instant throttle response needed for aggressive maneuvers.
This engine is also serving as a testbed for a future marine engine program, though Banks does not yet go into detail on that application. For now, the focus is on getting the current combination onto the dyno for its first fire. The recap closes with the engine essentially ready for that next step: a 427-cubic-inch Duramax with a dedicated blower drive, a carefully arranged accessory system, a single high-capacity injection pump, substantial alternator output, four MAF-based airflow measurement channels, and twin Precision 6870 turbos sized around a projected 1,400-horsepower target.