The real target is not boost pressure. It is manifold air density—the total air pressure and density actually pushing past the valve and into the cylinder. That is what determines air mass, fuel, and horsepower. On this monster truck engine, we logged ambient air density, blower-added density, rpm, airflow, and throttle behavior so we can fingerprint what the current 540-inch blown alcohol combination really needs. With that data, we can reproduce the load and response on the dyno, then define what the diesel has to deliver to match or beat it. That is why we use the Banks iDash 1.8 DataMonster: real data, replayable data, and a power target based on air mass instead of guessing from boost.
Gale Banks opens with the core challenge: replacing a Monster Jam monster truck's 540-cubic-inch, 1,400-horsepower blown alcohol engine with a diesel without losing the immediate manifold air density and throttle response needed in competition. To begin that process, Banks obtained Cynthia Gauthier's Monster Mutt Dalmatian truck, instrumented it with sensors, and installed the company's high-speed DataMonster logging system. The truck was then sent to San Jose so the team could capture real operating data from the existing combination before attempting to match it with a diesel.
The purpose of the exercise was not simply to record boost or RPM. Banks wanted a complete fingerprint of how the current engine behaves in the truck, especially during rapid throttle transitions, jumps, and donuts. That baseline would let the team reproduce the same operating profile on an engine dyno and determine what the diesel would need to deliver in order to equal or exceed the performance of the blown alcohol setup.
Banks frames the entire project around manifold air density rather than boost pressure. In his view, boost alone does not directly describe horsepower because a boost gauge shows only pressure above ambient and therefore leaves out a large part of the actual pressure acting on the air charge. What matters is the total pressure and resulting density in the intake manifold, because that is what pushes air past the valves and into the cylinders.
He refers to this as manifold air density, or MAD. It is the key variable because air mass determines how much fuel the engine can burn, and fuel quantity determines power output. In other words, without the required air mass, there is no path to the target horsepower. That principle applies regardless of fuel type, whether the engine burns alcohol, gasoline, diesel, propane, nitromethane, or something more exotic.
The truck's current engine is described as a 540-inch blown alcohol V8 making about 1,400 horsepower at 7,400 RPM. Banks used the logged data to observe airflow, throttle response, RPM behavior, and calculated horsepower during actual runs. He notes that the engine can move well over 1,000 cubic feet of air per minute and that the truck demands extremely fast response when the driver gets in and out of the throttle.
The DataMonster system records up to 100 channels at 20 samples per second and stores the information on a microSD card. Banks points out that a 4 GB card can hold months of data at that rate. He contrasts this with the much more expensive data loggers traditionally used by OEM engineering groups, saying Banks replaced systems costing around $60,000 with a package built around the company's iDash SuperGauge and DataMonster hardware. The iDash can display much of the information in real time, while the logger captures both displayed and non-displayed channels for later analysis.
Banks says every engine build should begin with a horsepower target, not with a boost target or a displacement target. In this case, the target is straightforward: 1,400 horsepower, because that is what the current alcohol engine produces. The complication is that the diesel will not be turning 7,400 RPM, so it will need to make that power under a different operating regime.
Using the alcohol engine's air-fuel requirements, Banks calculates that 1,400 horsepower requires 137 pounds of air per minute. From there, the real question becomes how much manifold air density is needed to move that amount of air through the cylinder heads and into the cylinders. That is the engineering problem he intends to solve on the dyno after reproducing the truck's operating profile from the logged data.
Banks breaks air density into three factors: pressure, temperature, and humidity. More pressure increases density, lower temperature increases density, and lower humidity increases density. He emphasizes that anyone who has designed cold-air intakes understands the importance of cooler air, because colder air contains more mass per cubic foot.
He then references the standard atmospheric correction used for dyno testing in the United States, SAE J1349. On that standard day, air temperature is 77 degrees Fahrenheit, pressure is 14.35 pounds absolute, and humidity is 0 percent. Under those conditions, air density is 72.2 pounds per 1,000 cubic feet. Banks uses that as a 100 percent reference point for manifold air density calculations. Rather than discussing density only in absolute units, he also likes to express it as a percentage of that standard-day baseline because it makes the numbers easier to interpret in conversation.
With that framework established, Banks explains how total manifold air density is built. First there is the ambient air density present in the arena. In the logged example, ambient density is about 99 percent of the standard-day reference. The blower then adds what he calls boost air density, which in this case is 43.9 percent. Adding those together yields a total manifold air density of 145 percent.
He also expresses the same requirement in mass terms. To make the combination work, the intake manifold needs an air density of 119 pounds per 1,000 cubic feet. Since the truck starts with roughly 71.5 pounds per 1,000 cubic feet from ambient conditions on that day, the induction system has to add the rest. Once manifold air density is known, multiplying that density by the engine's airflow in cubic feet per minute gives the air mass flow rate. That air mass flow rate determines how much fuel can be burned and therefore how much power can be produced.
Banks compares the air required per 100 horsepower for several fuels. For the blown alcohol engine, the figure is 9.8 pounds of air per minute per 100 horsepower, which is how he arrives at 137 pounds per minute for 1,400 horsepower. For gasoline, he gives a rule-of-thumb value of about 10 pounds of air per minute per 100 horsepower. For diesel, he uses roughly 12 pounds of air per minute per 100 horsepower, assuming a clean-running engine rather than one producing excessive smoke.
He notes that these similar air-demand figures can seem surprising because the air-fuel ratios are very different. The alcohol engine runs at about 4.9:1, a gasoline engine might be around 12:1 at full power, and a diesel might operate in the 16:1 to 18:1 range. Even so, the air required per 100 horsepower stays in a relatively narrow band, roughly 9.8 to 12 pounds per minute. That is why Banks keeps returning to air mass and manifold air density as the universal language of engine output.
The logged data is not used only for steady-state calculations. Banks replays actual runs on a set of gauges to study how horsepower builds, how quickly the engine responds to throttle input, and how rapidly RPM changes during competition maneuvers. He mentions seeing more than 7,000 RPM per second of rate-of-change, underscoring how violent and immediate the engine response must be in a monster truck application.
During playback, one gauge shows boost pressure, but Banks treats it as secondary because it tells only part of the story. The more important display is manifold air density, which he calls the holy grail. In one paused example from a run, the truck is making 1,078 horsepower with a manifold air density of 106 pounds per 1,000 cubic feet. That relationship illustrates his broader point: once air mass in the intake manifold is understood, it can be used to estimate horsepower directly.
After reviewing the truck's logged runs, including high-power donuts where the engine spends time above 1,000 horsepower, Banks concludes that the team now has enough information to move into dyno testing. He remarks that when the truck is held at more than 1,000 horsepower, it consumes roughly four gallons of alcohol, reinforcing just how much air and fuel the current combination uses.
The next step is to receive the engine being sent from Florida, install it in Dyno Cell 1, and reproduce the truck's real-world operating profile using the captured data. That dyno fingerprint will define what the diesel must achieve in terms of airflow, manifold air density, throttle response, and power delivery. Banks presents this as a deliberately unconventional engineering approach: rather than relying on traditional assumptions or simple boost targets, he intends to define the diesel conversion around measured air mass behavior and real competition data.