Mario Monette's 4,000-HP Compound-Turbo C15 Engine "The Beast" - Engine Builder Magazine
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The Beast

Diesel of the Week

Mario Monette’s 4,000-HP Compound-Turbo C15 Engine “The Beast”

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We’ve seen a lot of crazy diesels over the years, and we won’t lie and say we haven’t described one or two as a “beast.” But regrettably, we may have been wrong in our analysis. This week’s spotlighted diesel is literally named “The Beast,” and that might even be an understatement.

The diesel performance world is vast and continuously growing, but souped-up semi-trucks are still one sector that is relatively small. You’ll find some crazy builds if you do some searching, but generally, the art of building a performance big rig for racing or pulling is difficult to get into. That’s why when you do find one, it’s pretty likely you’ll be taken aback.

“The Beast” is one such creation, which in 2018, propelled owner Mario Monette down the 1/4 mile to achieve the NHRDA Hot Rod Semi MPH World Record at 120.35mph. It might seem crazy to imagine a 15,000-lb. 1988 Peterbilt 379 reaching those speeds in only a 1/4 mile, but it makes more sense once you realize it’s being powered by a behemoth, 4,000-horsepower, turbocharged, CAT C15 engine under the hood.

It takes a professional to build something that impressive, and Monette was the man for the job. His career started in 1987 when he started working as a mechanic in Montreal. With two degrees in Mechanical Engineering and Program Engineering, 17 years as a diesel mechanic for Detroit Diesel, and tuning experience that stretches back to the late ’90s, Monette isn’t short of experience in any regard.

He moved to Alberta in 2010 and started his company two years later. Mario High Performance Diesel is one of the leading custom programmers in the world for semi-truck and heavy-diesel engine applications. Monette and his team of two other programmers collect data from vehicles internationally, using proprietary equipment, then build out custom tunes to make the said engines soar.

The Beast was born out of passion, and Monette built almost every aspect of the engine on his own. All the machining and engineering was done in-house with mostly used parts.

“The engine is a C15 CAT but I say it’s C15-ish,” Monette told us. “I say that since all of the parts have been recycled from different engines and I’ve modified and machined them to fit on. I machined the pistons to where the engine is actually 17.3L instead of 15L.”

Monette left the stock crankshaft under the hood, but machined and polished his own rods. He also designed the copper head gaskets and had a shop in Edmonton cut them out.


The fuel system is based on a capsule, and the slender head is modified to run a FASS fuel system that provides 2,000 gallons per hour. The insane amount of fuel is transferred via four double fuel pumps.

“The reason for that is to get rid of the air and always keep 18 psi to the gear pump that provides the injectors that are at 250 psi. There’s a lot of flow I’m running on a 1″ hose to feed the engine. One run of the 1/4 mile takes four gallons of fuel.”

The air system is aided by a compound turbo setup, with a 118mm Precision turbo in the valley and a 143mm Precision turbo serving as the atmospheric charger. Monette used two wastegates to stop the setup at 220-lbs. of boost. If he wants to run higher amounts of boost, he simply cranks of the CO2 on the wastegates. Recently, he’s dropped that number down to about 180-lbs. of boost to put less pressure on the engine. Before, he was running through two cylinder heads a year after pushing it to its limits.

The one component Monette didn’t craft himself were the injectors. One of his friends provided him with 14mm plunger injectors, almost double the size of the stock 8mm CAT ones. Monette’s injectors will spray 725cc of fuel, almost six times as much as the 125cc stock injectors.

“We use a standalone ECM that I created with some people in the Netherlands because the Caterpillar ECM couldn’t take 4,000 RPM,” he says. “On the line, it’s at about 4,200 RPM on the 12th gear, it’s an 18-speed manual with a clutch pipe.”


It’s obvious why Monette has made a name for himself – 11-second passes in the 1/4 mile are pretty impressive for a big rig. But what’s more impressive is his dedication to the community.

Whenever he races, Monette holds a raffle for spectators to win a ride, most of them are children. All of the proceeds get donated to a children’s hospital in Alberta. In September, he plans on being in Pomona, CA with 10-4 Magazine for “Truckin’ for Kids,” a drag and show event that raises money for various children’s charities.

“My goal is to bring children and their families to the track and get more people invested in motorsports,” Monette says. “I let them get inside and play around with the truck. I built it so kids cannot break it.”


Your next chance to see The Beast in action is this weekend, June 3-5, at UCC 2022.

Diesel of the Week is sponsored by AMSOIL. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected]

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