Why V8 Engines Aren’t the Choice for Semi-Trucks
V8 engines are known for their powerful performance and distinctive sound, often described as “wicked awesome.” It’s natural to assume that such strong engines would power the large semi-trucks responsible for transporting most of the cargo in the U.S. However, this isn’t the case. Most modern semi-trucks are equipped with inline-6 engines instead.
There are several key reasons why V8s have become less common in the trucking industry. While a V8 produces impressive horsepower, towing heavy loads requires torque rather than just speed. Inline-6 engines used in modern semis typically generate between 400 and 600 horsepower, which is not significantly more than what a well-equipped pickup truck offers. This level of power is usually sufficient for most tasks.
However, the real advantage lies in torque. Semi-truck engines can produce between 1,000 to 2,000 pound-feet of torque. This is achieved through large engine displacements (ranging from 13 to 16 liters), turbocharging, and diesel power. These features allow the engines to handle heavy loads efficiently, something that V8s struggle with due to their design limitations.
Another factor is the weight limit for semi-trucks in the U.S., which is capped at 80,000 lbs. In Europe, companies like Scania use a 16.4-liter V8 producing 2,350 lb-ft of torque, but these vehicles are designed for heavier loads. A smaller inline-6 engine is more than capable of handling lighter American loads without any issues.
The Advantages of Inline-6 Engines
Some argue that the inline-6 configuration inherently favors torque over horsepower, but this isn’t entirely accurate. The amount of torque produced depends on factors like the piston stroke and cylinder size, regardless of the engine’s layout. However, the tall and narrow design of an inline-6 makes it easier to build with a longer stroke. Increasing the stroke in a V8 would make it wider and taller, which could be problematic under the hood of a semi-truck.
A longer stroke also means the engine can’t reach high RPMs as easily as a high-horsepower V8 with a shorter stroke. While this might seem like a disadvantage, it’s actually beneficial in the context of trucking. Lower RPMs reduce stress on the engine, leading to greater reliability and lower operating costs.
Simplicity and Efficiency
The inline-6 engine is simpler in design compared to a V8. It has only one cylinder head instead of two, resulting in fewer parts and easier maintenance. This simplicity also makes the engine more accessible for repairs, reducing both time and cost. Additionally, its low-revving nature contributes to better fuel efficiency, even if the difference is small. For trucks that operate on long distances, every bit of efficiency matters, especially when fuel economy is measured in miles per gallon.
Emission Regulations and the Future of Trucking
Stricter emission regulations have also played a significant role in the decline of V8 engines in semi-trucks. It’s easier to meet environmental standards with a smaller inline-6 engine than with a larger V8. As a result, most manufacturers have opted for inline-6 configurations. Some companies, like Caterpillar, have even stopped producing semi-trucks altogether, shifting their focus to off-road applications.
While electric options like the Tesla Semi may shape the future of the industry, the inline-6 remains the dominant choice for American trucking today. Its combination of torque, reliability, and efficiency continues to make it the preferred engine for hauling heavy loads across the country.
