This setup exposed the real problem with a roots blower on a diesel: boost alone does not mean dense, cool air. Spinning the 10-71 20% over crank delivered nominally 20 psi, but compressor outlet temperature was extreme, and the blower’s parasitic load was substantial. We pushed water-meth and straight methanol through it to cool the charge and see what the engine actually wanted. Water-meth helped torque and horsepower, and it did bring manifold temperature down, but not by much relative to how hot the blower was making the air. It also did not reduce EGT in this test. Straight methanol added more power, but it also pushed peak cylinder pressure dangerously close to top dead center. With pilot injection on, the pilot effectively lit the methanol early. Turning pilot injection off made the test safer, but higher methanol levels still got edgy fast. The takeaway is simple: this blower makes a lot of heat, water-meth is not a magic EGT fix, and straight methanol on a diesel-blower combination can get into detonation territory in a hurry. The instrumentation made that visible in real time, and the post-test inspection confirmed the hardware paid the price.
The build begins with an ambitious plan for a monster-truck engine: a twin-turbo, supercharged 7.0-liter Duramax. For this phase, however, the team chose to fully instrument the engine and run only the blower. The idea is to understand the supercharger by itself before adding turbos upstream. Gale explains that the eventual turbo-into-supercharger arrangement is intended to preserve low-speed throttle response, which is especially important in a monster truck where precise control is needed to balance the truck during aggressive maneuvers.
The engine uses a 10-71 Roots blower driven 20 percent over crank speed. At 5,000 engine rpm, the blower turns about 6,000 rpm, and at that speed it produces roughly 20 psi of boost with a compressor outlet temperature around 480 degrees Fahrenheit. That temperature is alarmingly high; Gale compares it to Ray Bradbury's Fahrenheit 451, the ignition temperature of paper, to emphasize that this is not air you want entering an intake manifold without some form of cooling.
To control blower outlet temperature, the team prepared two injected fluids. One was straight methanol. The other was the Banks Power blend: 50 percent methanol, 49 percent distilled water, and 1 percent corrosion inhibitor. Rather than run the engine at 5,000 rpm, they chose 3,200 rpm for sustained testing because it was a safer operating point for dry blower operation.
The test plan was methodical. They would first run the blower dry, then introduce the Banks Power blend in 20 percent flow increments while monitoring torque, manifold temperature, lambda, cylinder pressure, and other channels. After completing the water-methanol series, they would switch to straight methanol and repeat the stepped testing. Gale was particularly cautious about straight methanol because, although the fuel was around 112 octane, he had found little or no data on diesel engines using methanol overlay in this way.
The dry baseline quickly showed why charge cooling was necessary. Even at modest load, the blower heated the intake charge dramatically because it is mechanically driven and cannot back off the way a turbocharger can. At roughly 3,200 rpm, the engine was making only about 15 psi of boost and around 310 lb-ft of torque, yet manifold air temperature climbed into the mid-300-degree range and continued rising toward 400 degrees Fahrenheit.
At idle, the effect was already obvious. With the engine near 1,000 rpm and producing almost no useful power, the manifold temperature was still near 240 degrees. Gale notes that a turbocharger under those conditions would be largely unloaded and would add very little heat, but the belt-driven blower imposes compression and heating whether the engine needs it or not. That fixed parasitic behavior became a central theme of the test program.
Injecting the Banks Power blend produced an immediate reduction in manifold temperature, though not a dramatic one. The team completed a full sweep from no injection to level 10. Torque rose from 303 to 320, 338, 364, 384, and finally 410 lb-ft. Horsepower increased from 184 to 250 hp, a gain of 66 hp. Water-methanol flow progressed from zero to 0.50, 0.88, 1.18, 1.55, 1.89 lb/min, and at the highest setting the water-methanol mass slightly exceeded the diesel fuel mass, reaching about 1.15 lb of water meth per pound of diesel.
Manifold air density told a more nuanced story. Starting at 89.9 lb per 1,000 cubic feet in the intake manifold, density initially dipped slightly as vaporized water and methanol displaced some oxygen-bearing air. Once injection reached higher levels, cooling began to dominate, and density rose. By level 10 it reached 93.2 lb per 1,000 cubic feet. Lambda moved from 1.52 down to 1.20, showing that the engine still had excess oxygen available and could have accepted more fuel before reaching lambda 1.00.
Temperature reduction across the blower was real but limited. Manifold air temperature fell from 326 degrees Fahrenheit dry to 320, 315, 309, 301, and finally 292 degrees at level 10. That was only a 34-degree drop. Gale contrasts this with spark-ignited methanol monster-truck engines, which run so much methanol through an 8-71 blower that intake manifold temperatures can stay below 100 degrees under full load. In this diesel application, the blower's inefficiency remained the dominant factor.
One of the most important findings was that water-methanol injection did not reduce exhaust gas temperature. This directly contradicted a common claim in the diesel aftermarket. On straight diesel, EGT was 1,151 degrees Fahrenheit. As water-methanol flow increased, EGT rose to 1,185, 1,224, 1,256, 1,277, and finally 1,285 degrees. Instead of cooling the exhaust, the added methanol acted as additional fuel and increased combustion energy.
Gale argues that the usual explanation for water-methanol benefits is incomplete. Yes, water absorbs heat through latent heat of vaporization as it changes state, but the methanol portion is still a combustible fuel. The net result in this test was higher exhaust temperature, not lower. He also challenges the popular "steam engine" theory that vaporized water itself adds meaningful power. That claim would be tested more directly later by comparing matched methanol-content cases.
Before the formal methanol series, the team ran exploratory tests and encountered a serious combustion problem. With pilot injection active at 41 degrees before top dead center and main injection at 8 degrees before top dead center, they added methanol in steps up to roughly a 1:1 methanol-to-diesel mass ratio at 3,200 rpm. Torque climbed from 227 to 291, 349, and 381 lb-ft, while horsepower rose from 138 to 177, 213, and 232 hp. Methanol flow increased from 0.67 to 1.09 and 1.49 lb/min, with the final ratio reaching about 1.06:1 methanol to diesel.
Those gains came with a dangerous shift in combustion phasing. Peak cylinder pressure rose from about 88 bar to 104 and then 123 bar. More importantly, the crank angle of peak pressure moved from 11.6 degrees after top dead center on diesel alone to 8.6, then 6.2, and finally just 2.6 degrees after top dead center. Gale concluded that pilot injection was initiating methanol combustion too early. In effect, the diesel pilot acted like a spark plug for the methanol, advancing the burn and pushing peak pressure dangerously close to TDC. He judged this a non-starter and decided that all subsequent methanol testing would be done with pilot injection turned off.
With pilot injection removed, the team repeated the straight methanol series more cautiously. Starting again from 303 lb-ft and 184 hp on diesel alone, torque increased to 331, 372, 413, and 442 lb-ft through levels 2, 4, 6, and 8. Horsepower rose to 201, 227, 251, and finally 269 hp, an 85 hp gain. Methanol flow rates were lower than in the water-methanol series because the team remained wary of detonation: 0.25, 0.50, 0.84, and 1.22 lb/min. At level 8, the methanol-to-diesel ratio reached about 0.73:1.
Lambda still showed excess oxygen, moving from 1.56 to 1.14 by the end of the test. Manifold temperature reduction was modest, only about 16 degrees, and EGT again increased rather than decreased, rising from 1,176 to 1,317 degrees Fahrenheit. Cylinder-pressure timing also advanced substantially. On diesel alone, peak pressure occurred about 12.5 degrees after top dead center. With straight methanol, it moved to roughly 5.5 degrees after top dead center by the highest level. Gale describes the engine as getting "raucous" at levels 6 and 8, and the pressure trace resembled detonation in a gasoline engine. His conclusion was that the methanol's nominal 112-octane rating was not enough protection under these diesel-initiated combustion conditions.
The comparison between matched methanol-content tests provided one of the clearest conclusions of the session. Gale compared straight methanol at level 6 with water-methanol at level 10 because both cases added the same methanol mass: 0.84 lb/min, or about 7.6 gallons per hour. The water-methanol case also added 1.05 lb/min of water, about 7.55 gallons per hour.
The water-methanol case did improve intake conditions. Manifold air density increased from 21.8 to 24.6 lb per 1,000 cubic feet because the cooling effect condensed the charge and made it denser. But power did not increase. Straight methanol at level 6 produced 251 hp and 413 lb-ft, while water-methanol at level 10 produced 250 hp and 410 lb-ft. The outputs were essentially identical. Gale's interpretation was straightforward: the added power came from the methanol fuel, not from steam generated by the water. The so-called steam-engine effect contributed no measurable horsepower in this comparison.
The data also exposed how costly the blower was in parasitic power. On straight diesel, brake specific fuel consumption was about 0.507 lb per horsepower-hour, far worse than the roughly 0.400 lb per horsepower-hour expected from a typical turbocharged diesel. Using the same fuel flow and dividing by 0.400 suggested that a turbocharged version making equivalent airflow would produce about 50 more horsepower at 3,200 rpm. In other words, the supercharger itself was consuming roughly 50 hp from the crankshaft.
After the testing, a leakdown check showed 10 to 15 percent leakage, with cylinder number one at 15 percent. Borescope inspection revealed cylinder-wall damage, indicating that foreign material had passed through the engine. Inspection of the blower explained why: the hard anodizing had been worn through, and aluminum transfer was visible. Gale traced the problem to blower clearancing. He had purchased the blower with gasoline clearances, which are looser than methanol clearances, and not with clearances suitable for dry operation. The resulting contact and material shedding likely caused the wall damage. At minimum, the engine would need to be torn down, the cylinder walls cleaned up, and the rings replaced, with further inspection needed for piston skirts and blower condition.
By the end of the session, the team had learned several hard lessons. Water-methanol reduced manifold temperature only modestly and did not lower EGT. Straight methanol added more power but pushed combustion toward detonation, especially if pilot injection was used. The steam-power explanation did not hold up. And the blower itself imposed major parasitic loss while also suffering hardware damage under the chosen clearances. The experiment produced valuable data, but it also made clear that the combination would need significant rethinking before moving on to the full twin-turbo blown Duramax concept.