ATC Blog

The Extraordinary Engine Configurations of 18-Wheelers

The loud, massive 18-wheel trucks you see barreling down the highways, referred to as semi-trucks, play an important role in the transportation of goods and supplies across our country. But to do so, they need powerful engine configurations.

ATC’s Diesel Technology course teaches our students the mechanics of diesel engines, such as the ones found in semi-trucks, so they can go on to fulfilling careers as diesel and heavy equipment technicians. Continue reading for a glimpse into the engines that power the semi-trucks you see on the highway.

Requirements of Semi-Trucks

Semi-trucks usually measure in at 53 feet in length. Primarily used for the transportation of everything from food to furniture, sometimes these trucks have to travel massive distances, even cross-country, to reach their destination.

Each year, a well-working business relying on ground transportation will require a semi-truck to travel an average of 45,000 miles—some years even closer to 100,000 miles—while carrying a trailer that, when packed, can weigh close to 80,000 lbs.

This distance is difficult to travel because these trucks average about 5.6 mpg on the highway using diesel fuel. This mileage rating goes down when traveling uphill but also goes up when rolling downhill. Revisions to the builds of these trucks are constantly being made to improve the aerodynamics and prevent wind turbulence in an effort to improve the fuel economy.

Needless to say, semi-trucks need a strong engine configuration in order to travel the amount of ground required with a full trailer weighing them down.

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Engine Configuration

As expected, engines in semi-trucks are huge, and they need to be in order to move all of the trailer weight. The Detroit Diesel DD15 is a semi-truck that boasts a 14.8-liter inline six-cylinder diesel engine that weights 2,880 lbs. This big engine isn’t built to provide a semi-truck with horsepower, as it only generates 506 horsepower, but rather to provide torque.

Torque is what helps semi-trucks tow all of that weight behind them. So for this specific truck to carry 80,000 lbs, it needs to generate 1,850 lb-ft of torque—sometimes even more to keep the weight moving and all 18 wheels turning. The fuel tanks inside these semi-trucks are massive in order to combat the weak fuel economy.

While stigmatized as obnoxious gas guzzlers, the semi-truck industry is a huge part of our economy and the significance of these vehicles can’t be understated. And for automotive enthusiasts, their engine configurations are a thing of pure beauty. The massive engines provide insane amounts of torque and are strong enough to turn 18 wheels while carrying 80,000 lbs over tens of thousands of miles.

If this type of engine configuration interests you, then you can dive deeper into the world of semi-trucks and diesel engines with ATC’s Diesel Technology course.

For more information and insight on different engine configurations, you can download ATC’s free ebook Facts and Myths About Hybrid Engines.

Hybrid Facts and Myths

For program disclosure information, please go to www.autotraining.edu/consumer-information.

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