This engine program is being built around the weak links you hit when a diesel has to act like a monster truck engine. We’re not just stacking boost on an L5P and hoping for the best. We’re measuring blower mass flow, air density, outlet temperature, methanol distribution, coolant flow, oil aeration, pump speed, and crankshaft packaging so the combination can live under real load. A big part of the work is controlling heat and pressure. Methanol is being used as both fuel support and charge cooling, with nozzle placement and control strategy aimed at fast response and even distribution. On the L5P cooling side, the front water outlet casting becomes a restriction when EGR hardware is removed, driving block pressure up and creating an overheating risk if it isn’t modified. Oil control matters just as much, so the dry-sump layout, pressure-stage routing, and larger oil-cooler plan are all being worked out together. The hard parts are the details. Slowing the injection pumps to stay in a safe speed range, moving the crank trigger to the front damper instead of machining away rear counterweight, evaluating stock L5P pistons and cooling nozzles, and improving exhaust-side flow are all part of making the engine survive at the rpm and load this application demands. That’s the point of the testing: find the limits, fix the failure points, and build a Duramax that responds like the alcohol engines without giving up durability.
The team is preparing an L5P Duramax fitted with an 8-71 blower, with a 10-71 also available for comparison. The 10-71 is currently on the engine, and the immediate goal is to measure mass airflow into the blower. To do that, they are setting up a dual-inlet hat with two 4-inch mass airflow sensors. Each sensor is expected to support roughly 260 pounds per minute, giving about 120 pounds per minute per side in the intended configuration.
The broader objective is to make the diesel respond like a methanol-fueled monster-truck engine. Gale wants to understand how quickly the engine comes up against torque-converter stall, especially because the converter used in blown Chevy monster-truck applications is very loose. By reviewing RPM versus vehicle speed data from prior monster-truck testing, the team expects to identify the point where vehicle speed and engine RPM begin to converge as the converter loads. That flash characteristic is important because the diesel combination is being developed to deliver a similarly aggressive response.
The initial testing will be done with the blower alone, followed by blower operation with methanol injected at the hat. Gale prefers the idea of using methanol above the engine rather than stacking additional intercooler height beneath the blower. Packaging is already becoming difficult, and avoiding another four inches of intercooler core under the supercharger would simplify the installation.
The methanol system itself is still in prototype form. The Banks control hardware is at the beta-testing stage, and the core firmware is functional but still needs refinement. Even so, the team believes it is ready enough to support development work. The expectation is that methanol injection will provide meaningful intake-air cooling. On Banks' blown 548 Chevy, intake manifold temperatures stayed relatively cool, and Gale expects a similar benefit here.
The blower is being started at about 20 percent overdrive. That is a conservative entry point, intended to let the team creep up on boost, blower outlet temperature, and the resulting air-density changes. They plan to measure air density both in the dyno cell and in the intake manifold so they can quantify density loss from temperature rise across the blower and density gain from pressure increase. When methanol is added, Gale expects manifold air density to increase substantially.
Because the blower is set up to gasoline clearances rather than methanol clearances and does not use Teflon strips, it is considered relatively loose and therefore safe for this early work. The team does not expect to push enough liquid through it to create hydraulic concerns. For now, they would rather put all of the methanol in the hat than split it between multiple systems. Exhaust-port thermocouples are already installed on every cylinder, so mixture distribution can be evaluated by comparing exhaust temperatures.
The target operating range is informed by prior monster-truck experience. The blown alcohol Chevy combination had been run to around 6,000 RPM, with 6,300 RPM becoming questionable because of external counterweight issues that have since been addressed. Gale also wants to verify how high the Monster Mutt Dalmatian engine was actually turned, recalling that it may have reached 7,000 RPM and sustained roughly 5,000 RPM during long donuts while making an estimated 1,100 to 1,250 horsepower.
Ideally, the L5P Duramax would operate in a similar RPM band and deliver a similar response. However, the high-pressure fuel pump becomes a limiting factor. The current development path starts with a Bosch system, though Gale ultimately wants to evolve toward a Denso HP4 arrangement like the production L5P uses. Based on pump-speed limits versus rail pressure, the team believes 3,500 pump RPM is the practical ceiling if they want to maintain 2,000 bar rail pressure safely. Pushing to 3,600 RPM moves into a region Gale considers too risky, so 3,500 RPM is the working limit.
To allow higher engine speed without overspeeding the pumps, the Bosch CP3 pumps will be underdriven. The team already has larger pulleys, but the hubs that adapt those pulleys to the CP3s still need to be machined. Their target is to slow the pumps to roughly the mid-60-percent range of crank speed. With a 40-tooth pulley, they expect to keep pump speed in a reasonable range up to about 6,200 engine RPM, which is close to the desired operating window without sacrificing too much low-speed pump performance.
While running the L5P at 3,500 RPM, the team discovered a serious coolant-flow restriction in the cast aluminum Y-shaped outlet that joins the front of the cylinder heads into the dual-thermostat housing. Because this engine is being run without an EGR cooler, all coolant must pass through the thermostats, and the restriction in that casting drives block pressure excessively high.
Before modification, block pressure at 3,500 RPM was around 75 PSI. After Mike opened up the casting, that dropped closer to 50 PSI, which is still high but much improved. Pressure across the water pump is currently about 50 PSI or slightly more at that speed. Gale emphasized that anyone performing a full delete on an L5P without modifying that outlet duct is likely to create overheating problems. The issue also affects oil cooling because coolant flow through the oil cooler is part of the same system.
The engine is currently using a 17-by-19 oil cooler, but the plan is to move to a 20-by-20 cooler. For the monster-truck engine, Gale would like to use the same 20-by-20 cooler if packaging allows. Bob was asked to study how oil will be routed into and out of the cooler with the dry-sump system, since that may require drilling, tapping, plugging, or fabricating custom passages.
The coolant-flow test data confirmed that the system had reached the limit of its measurement hardware. The team had been seeing flow values flatten at about 100 gallons per minute while pressure continued to rise from roughly 2,400 RPM upward. That combination does not make physical sense if the system is truly flowing more coolant, so the likely conclusion is that the flow meter itself has saturated.
The installed transducer is nominally a 144-gallon-per-minute unit, but in practice it appears to behave more like a 100-gallon-per-minute meter. The trace begins to roll over before the flatline, and the raw data becomes fuzzy as it approaches the upper range. The sensor is a paddlewheel type, so both pipe inside diameter and paddlewheel intrusion into the flow are critical. The team confirmed that it is mounted in a 2.5-inch pipe, which should theoretically support much more range, so something about the installation or sensor configuration still needs to be checked. If the setup is correct, they will need a larger-capacity flow transducer.
The thermostats themselves do not appear to be the restriction. Mike had already calculated thermostat stem temperature versus opening position for the 82 C and 85 C thermostats, and they are controlling outlet temperature at about 208 to 209 degrees Fahrenheit while being fully deployed. The restriction was traced instead to the modified casting associated with the deleted EGR-cooler flow path.
The monster-truck engine will use a dry-sump system, and the team is still deciding how to mount the tank in the dyno cell. One option is to adapt a previously built vertical post and attach it to the test cart, but Gale wants any mount heavily triangulated because vibration will be severe. Although he is not entirely comfortable with the tank being mounted in a way that effectively follows engine vibration, he notes that monster-truck engines are hard-mounted in the chassis anyway, so the real-world environment is similarly harsh.
Aeration testing is a priority. The dry-sump tank is supposed to separate oil and air effectively, but Gale wants a petcock added so samples can be drawn and checked. His goal is to keep aeration below about 5 percent, with 7 percent considered the upper acceptable limit.
On the pressure side of the dry-sump pump, the team intends to feed oil into both ends of the engine, as they had done on earlier combinations. One pressure stage would enter through the traditional oil inlet after the oil cooler, while the other would feed a drilled and tapped opening low on the right side of the block near the pan rail and front cover area. That passage may feed the cooling nozzles and possibly the mains on that side. Gale likes the dual-entry approach because it helps maintain more consistent oil pressure through the system and better supports the front of the crankshaft.
Beyond getting the engine into the cell, the next major development area is airflow through the L5P heads. Mike was asked to begin working on port shapes for the L5P specifically. The exhaust port already flows better than earlier Duramax heads, and the intake port is shorter, but the intake side is still difficult to improve because of the geometry. One idea is to mill the end of the rectangular intake opening to create a straighter shot into the port.
Valve sizing is also under consideration. The stock arrangement is approximately 33 mm intake and 31 mm exhaust. Gale is interested in cleaning up the intake valve pockets and possibly moving to 33 mm exhaust valves if they will clear the stock bore. His goal is to bring exhaust flow closer to intake flow, which is especially valuable on a turbocharged engine where air is boosted in but restricted on the way out.
He is particularly impressed with the stock L5P piston, calling it the best production Duramax piston he has seen. The piston uses a laser-enhanced rim around the combustion bowl, which is believed to raise melting temperature somewhat, though the exact margin is not yet known. Gale wants to push the stock L5P piston as far as possible before moving to something more specialized. He also wants ring-pack specifications reviewed to determine whether the stock components are light enough, and whether gas loading is sufficient, to support operation near 6,000 RPM.
The production L5P oil nozzles are essentially the same as the race nozzles Banks has already used, matching within a couple thousandths, so they should flow similarly. With the dry-sump system in place, the team expects to remove restrictors when they begin adding more nozzle flow. The next question is whether an enhanced nozzle can be developed to exceed stock flow while still retaining the stock piston.
The rotating assembly will combine parts from different Duramax generations. Banks plans to use its earlier LML-style billet crankshaft with larger rod-journal pins in the L5P engine, along with custom rods once wrist-pin dimensions are confirmed. The L5P deck height is about 4 mm taller, so rod length will increase by roughly that amount, and the pistons will be allowed to protrude about 0.013 inch. Gale also wants to verify gasket compressed thickness, which he recalls being around 0.038 to 0.039 inch.
A major change is the relocation of crank triggering from the rear of the crankshaft to the front vibration damper. Teeth will be machined into the back side of the damper, and a crank-position sensor will read from the outside. Gale strongly prefers this arrangement because the factory rear trigger requires machining away part of the rear counterweight and uses a three-bolt mounting pattern that compromises counterweight integrity. He wants to preserve as much counterweight as possible and get the balance factor as close to zero as practical, adding external counterweight only if necessary and not in excess.
The immediate action item is to move the blown engine into Dyno One and begin installing instrumentation. Gale emphasized that once the engine is physically in the cell, the entire project mindset changes because the team can start debugging sensors, plumbing, and controls while outside fabrication continues.
Mario is finishing the blower hat, which Gale described as looking like an interleague barn door without a throttle body. The two mass airflow sensors will be mounted vertically. The methanol nozzles will likely be installed in the hat walls rather than the bottom plate, because the walls are about three inches tall and provide better packaging. Four nozzles are planned initially.
These are not conventional water-meth nozzles sized by interchangeable orifices. Banks has developed a methanol-impervious nozzle architecture intended for straight methanol use. The injector seals with an O-ring through an adapter, and fuel is fed directly into the top, eliminating the need for a conventional fuel rail. The spray pattern is conical, around 30 degrees, so nozzle angle and wall targeting matter. A 45-degree mounting angle appears to be a good starting point.
The nozzle strategy also reflects a broader Banks preference for pulse-width-modulated nozzle control rather than varying pump speed. PWM at the nozzle gives nearly instantaneous flow changes with each duty-cycle adjustment, whereas pump-speed control responds more slowly. That same philosophy may later be applied to other ducted applications, including the company's monster-truck Ram systems.
Finally, Gale discussed a major dyno upgrade underway with Froude in the UK. The new absorber and control system for Dyno Two is expected to handle about 3,600 lb-ft and 2,000 horsepower at steady-state full load, with flash readings in the 3,500 to 4,000 horsepower range and possibly approaching 5,000 lb-ft of torque. With oil-mist cooling, maximum speed is expected to be 9,000 RPM. That capability will support not only this diesel program but also future high-output gasoline and methanol engine testing.