Enhancing performance of the 6.6L Duramax L5P diesel engine that powers '17-to-current GMC and Chevrolet trucks is not an easy proposition. General Motors' calibration engineers have made it very difficult to manipulate the engine control modules that govern these engines, implementing code that essentially locks users out of critical fuel, timing, torque-management, and other tables. Of course, doing this renders traditional handheld programmers useless on these applications.
Despite the limitation, many new Sierra and Silverado owners still want improved performance from the latest Duramax V-8 without sacrificing any of the driveability dialed-in by factory engineers. Enter Banks (formerly Banks Power) and its Derringer inline programmer for 6.6L Duramax L5P-equipped rigs.
In our January 2019 issue, we detail and extol the Derringer's virtues, describing it as one of the only plug-and-play microcomputers available for the L5P platform. In addition, the unit is capable of tacking on an additional 61 hp and 112 lb-ft of torque ("Get Inline," page 76).
In their never-ending effort to improve performance and extract more power from the L5P, Banks engineers discovered the simplest and most efficient way to further enhance the oil-burner's capability is by modifying airflow into and out of the engine.
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The stock air intake system on L5P-equipped GM trucks draws fresh air from the fenderwell and hood scoop but does not take advantage of all the cool air available. The original assembly also restricts the amount of air that can enter the box. So, to fix these inherent problems and take advantage of all the good air available, Banks developed the Ram-Air Intake System.
Engineered to let an abundance of cool air into the engine, the Ram-Air Intake System uses the same openings as the stock airbox at the fenderwell and the hood. However, the new unit allows larger quantities of air to flow from these locations. There is also a third opening in the bottom of the box that draws air through the opening that exists between the front air dam and the plastic wheelwell liner.
All the air passes through an oversized filter. Banks claims that when combined with Derringer, the system yields an additional 81 hp (20 hp as a standalone modification). Also, like the programmer, the 50-state-compliant Ram-Air Intake has a California Air Resources Board Executive Order number.
Increasing the amount of air entering an engine means there is ultimately more that needs to exit. To address this requirement, Banks developers created a 5-inch Monster Exhaust System for '14-to-'19 Duramax-powered GM trucks. This less restrictive DPF-back pipe reduces backpressure by as much as 85 percent and lowers the exhaust temperature by 15 percent, significantly reducing the chances of any heat damage to the surrounding area during a DPF regeneration.
| Banks employee Curtis Androus loads the bed on the GMC with two 1,000-pound bags of sand before strapping the truck down on the dyno. The weight helps simulate how a truck is typically used.
To learn whether the Ram-Air Intake and the Monster Exhaust really make a difference, we took a trip to Banks Power in Azusa, California, and put the enhancements to the test on the company's Mustang Dynamometer. Upon arriving at Banks, we met Griffin Steinfeld, whose '17 GMC Sierra 2500HD Denali was scheduled to have the exhaust and intake installed.
Griffin's rig was previously outfitted with a Derringer and accompanying Banks iDash 1.8 Super Gauge and Data Monster. As a big fan of the performance gain Derringer already provided, Griffin was anxious to see what the new enhancements do for his truck. Read on to find out how this experiment went.
| Curtis uses the iDash Super Gauge and Data Monster to confirm the Derringer is set to the stock ECM tune and that the dyno runs will be data-logged.
| In the baseline dyno run, the 6.6L Duramax L5P in Garrett's '17 Denali produces 401 hp and 885 lb-ft of torque.
| Once the dyno session is complete, the truck is brought into the shop and positioned between the uprights of the lift and the hood is raised. The first order of business is to install the Ram-Air Intake System.
| The restrictive stock air intake tube includes a resonator that prevents the tube from taking advantage of all the cool air available.
| Here's a look at the Banks Ram-Air Intake and Monster Exhaust systems.
| Banks Brand Manager Jay Tilles removes the stock air intake.
| The opening in the fenderwell is actually much larger than the aperture in the airbox adjacent to it. With the two boxes next to each other, it is easy to see the Ram-Air's design takes advantage of the large opening, which definitely promotes more airflow.
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| A look at the bottoms of both airboxes reveals a significant difference. The Banks unit has a large rectangular opening that takes advantage of the cool air available from the open space beneath it. This space is fed from an opening that exists between the front air dam and the plastic wheelwell liner (the light seen in the picture looking straight down through the airbox mounting location).
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| Jay installs the supplied gasket material on the Ram-Air box's hood and fenderwell openings so it seals properly and keeps hot air out of the engine's air supply. He then installs the unit.
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The mass airflow sensor, air cleaner, and silicone boot are installed on the air-intake tube prior to bolting it in the truck. The larger (than stock) air filter and higher flowing intake tube (which eliminates the resonator) supply ample amounts of air to the diesel, and the fit complements the engine bay.
| The sticker with a California Air Resources Board Executive Order (EO) number is placed under the hood so it can be easily seen. The EO number confirms the Ram-Air intake is legal in all 50 states.
| Once the Ram-Air is installed, the truck is elevated on the lift so the Monster Exhaust system can be installed.
| The exhaust exits rearward, which can be an issue when towing a trailer and an emissions-system regeneration occurs. The extremely hot gases of the regen can damage the front of a trailer.
Curtis removes all the sensors in the exhaust behind the DPF. He then measures 7 inches back from the exhaust hanger (per installation instructions) and marks the pipe for cutting. A reciprocating saw makes short work of resizing the tube.
| After cutting the pipe and removing the hangers from the rubber isolators, Curtis weaves the exhaust from under the truck.
| Before installing the front section of the Monster Exhaust, Curtis uses a sanding disc to clean up the tube where the cut was made. The clamp is only lightly snugged at this time, so the exhaust pipe can be adjusted for a proper clearance once the rear section is installed.
| The end of the Monster Exhaust tube (where it goes into the tip) is 5 inches in diameter, while the end of the stock tubing reduces down to not quite 3 inches. The large free-flowing Banks pipe reduces backpressure that is commonly associated with the stock exhaust.
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| Curtis installs rear section of the new exhaust and the large polished tip. The clamps are only snugged at this time.
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| Once the exhaust tubing is properly positioned, the clamps are tightened and the sensors are installed in their corresponding ports.
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| Unlike the stock exhaust, the Monster exits on the side of the truck, behind the rear wheel. The larger system reduces EGT by 15 percent, making it much safer to use with a trailer.
| With the installations complete, the truck is put back on the dyno with the sandbags for another run.
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| This time, the '17 GMC Sierra 2500HD Denali is tested with the Derringer set at its highest power level to see what differences the modifications make. Based on previous evaluations, we know that as a standalone upgrade, the Derringer adds 61 hp and 112 lb-ft of torque. Those values increase to 98 hp and 125 lb-ft with the Banks Ram-Air and Monster Exhaust for a total of 499 hp and 1,010 lb-ft.
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| The graphs represent the baseline run (stock ECM calibration) and the 98hp, 125-lb-ft collective increase due to the addition of the Banks Derringer, Ram-Air Intake System, and Monster Exhaust on our test 6.6L Duramax L5P.
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