The real issue in dyno testing is not just making boost. It is controlling charge air temperature the same way the engine sees it in the vehicle. That is why we reworked Dyno 2 around a dual overhead air-to-water intercooler setup for the 2024 Duramax L5P program. This system lets us control water flow through each cooler independently, so we can duplicate different charge air cooling strategies instead of guessing at them. We can simulate a conventional air-to-air system, a liquid-coupled air-to-water system, or true intercooling between compressor stages on compound setups. That matters because charge air density is where the power comes from. Cool the air efficiently with low pressure drop, and the engine keeps making power without turning the dyno cell into a science project. The intercooler core itself is built for sustained abuse, not a quick pull. It uses corrosion-resistant core material, large inlet and outlet passages, reinforced structure, and a double-pass water side with a single-pass air side. In this configuration, one unit can support about 1200 horsepower on a diesel engine continuously. With two in Dyno 2, we are not going to run out of charge air cooler while testing the new 470-horsepower 2024 Duramax.
The video opens in Dyno 2, which has recently been occupied with government work rather than the usual public-facing engine development. Gale explains that the cell has been used for high-horsepower hybrid Army vehicle programs, and he limits the discussion there. He does note Banks' ongoing role in the JLTV, the Joint Light Tactical Vehicle, where the company supplies its Banks-modified version of the Duramax L5P. According to Gale, that program is approaching 20,000 engines, and Banks has also been selected for the next JLTV variant, the A2.
The engine on display is identified as an A2 L5P received from Duramax and then "Banksed" at Duramax. Gale points out that the lower crankcase carries Banks casting identification, although it is only visible from underneath. That lower-end package is described as handling oil control functions including anti-aeration, temperature reduction, and horsepower improvement, while also helping the engine tolerate the significant tilt angles encountered in military vehicles.
He also frames this engine as the first Banks second-generation L5P to be shown publicly. For pickup-truck trim, the newly announced output is 470 horsepower and 975 lb-ft of torque. He compares that with the first-generation L5P and notes gains of 25 horsepower and 65 lb-ft. Although he says there is much more to cover on the engine itself, that deeper teardown and comparison is reserved for a later video. The focus here is the charge-air-cooling system used in the dyno cell.
The main subject is how Banks performs charge-air cooling in the dyno environment and how the setup can replicate liquid-coupled systems. Gale describes the dyno-cell arrangement as air-to-water, which is also the approach Banks uses on many marine engines and on a number of racing applications, especially at Bonneville.
He contrasts the current update with an older charge air cooler design that had been in service since roughly 2000. That earlier core design had been used on Cummins-based twin-turbo engines built for the Navy, on experimental marine V8 engines in both twin-turbo and super-twin-turbo configurations, and on the Dakota that ran at Bonneville. The same general style also appeared on vehicles used during the Hot Rod Power Tour, including several diesel trucks and a twin-turbo small-block 1990 Chevy short-bed that had originally been a 454 SS.
Gale explains why the charge air coolers are mounted overhead rather than on the floor, and why the dyno setup now uses two units. In compound-turbo systems, he says, it is desirable to cool the charge air between the first compressor and the second compressor. That intermediate cooling stage is the original reason for the term intercooler.
With the overhead water-fed arrangement, each cooler has its own controllable flow path, visible through the valves in the system. That allows Banks to vary coolant flow through each unit independently and reproduce the behavior of either an air-to-air intercooler used in a vehicle or an air-to-water system. The key metric is the increase in air density achieved through the cooler. Gale emphasizes that this density improvement is what drives power production, and he makes the broader engineering point that the intercooler can contribute more power gain than the turbocharger or supercharger itself because reducing charge temperature raises air density so effectively.
At the bench, Gale walks through the intercooler assembly itself. He notes first that it is heavy, and that if it had been made as a casting it would weigh less. These particular units, however, were machined from billet. The design begins with the core, which uses 90/10 copper-nickel or brass on the water side. That material choice comes from the system's marine origins, where the cooler may be exposed to seawater, salt water, or similarly corrosive environments such as Bonneville's salt conditions.
Because of those origins, the assembly uses premium materials and is intentionally built for durability rather than minimum weight. Gale describes it as a highly efficient system in both temperature recovery and low pressure drop. Flow capacity is supported by large inlet and outlet elbows so that the full surface area of the core is used on both sides without masking or distorting the flow path. Reinforcements on the top and bottom prevent the structure from oil-canning or bursting even if boost pressure reaches the hundreds of PSI in a large compound-boost application. The billet housing is described as extremely stout for the same reason.
The water circuit in this intercooler is configured as a double pass. Gale points out a separator at the front end of the charge air cooler that divides the flow. Water enters and travels through half of the core, reaches the turnaround cap at the far end, and then returns through the other half of the core. In his summary, that makes it a two-pass system on the water side and a single-pass system on the air side. He also restates it as two-pass on the cold side and one-pass on the hot side, depending on how one prefers to describe the heat exchanger.
Gale then outlines the assembly sequence in detail. A Viton O-ring is first slipped over the core and moved down to the front flange. The core is inserted into the housing until it contacts the front sealing surface for that O-ring. Another O-ring is placed on the turnaround cap, and the turnaround cap is inserted into the rear of the core.
Next, the turnaround-cap cover is installed. That cover includes a tensioning bolt, which is later adjusted until it contacts the turnaround cap so the cap cannot be pushed out of the core under pressure. At the front of the assembly, another O-ring seals the water-supply cap to both the front of the core and the housing. After those fasteners are tightened to torque, the tensioning bolt is advanced until it touches and is then locked with a jam nut. The final major pieces are the inlet and outlet elbows. Gale adds one last omitted detail: the drain fitting, which completes the assembly.
He also notes an important alignment requirement. The core must be rotated so that the flat on the outlet surface and the flat on the core are parallel. Before the cap bolts are tensioned, that orientation has to be square and correctly positioned.
Using this core and housing style, Gale says a single intercooler can support about 1,200 horsepower on a diesel engine continuously in seawater service. In the dyno cell, where coolant flow and conditions can be controlled precisely, the system can simulate a wide range of real-world charge-air-cooling arrangements.
That includes duplicating ocean conditions for marine work, reproducing a liquid-coupled air-to-liquid-to-air system like one used in a vehicle, and placing intercooling between the first and second compressors in a compound-turbo setup. The same flexibility applies to combinations involving a supercharger feeding a turbocharger or a pair of turbos. His conclusion is that with this pair of intercoolers installed in the dyno cells, Banks will not run out of charge-air-cooling capacity during testing.
The video closes by tying the cooling-system discussion back to the 2024 Duramax program. Gale says the pair of intercoolers will be shown in operation when the 2024 Duramax is run on the dyno. Before that happens, however, he plans to tear down the new second-generation L5P and show what has changed internally compared with the current engine. This episode therefore serves as a technical introduction to the dyno-cell charge-air-cooling hardware that will support that upcoming engine analysis and testing.