The Smallest Displacement Inline-Six Ever Produced

The inline-six engine has long been celebrated for its smooth power delivery and balanced design. In automotive engineering, larger displacements have often been favored to maximize performance. However, there is a unique and intriguing corner of the automotive world that used the smallest displacement inline-six engines ever produced.

These pint-sized power plants may lack the impressive displacement of their larger counterparts, but they make up for it with their efficiency, packaging advantages, and sometimes even surprising performance capabilities. Auto manufacturers that have produced these small engines have included them in a variety of models. From economy cars to sports coupes, these small-displacement inline-sixes have left a lasting impact on the automotive industry.

In order to give you the most up-to-date and accurate information possible, the data used to compile this article was sourced from various manufacturer websites and other authoritative sources, including Stellantis and Spyker.

The Smallest Inline-Six Engine

Straight-six or inline-six engines are not generally associated with small-displacement engines. Typically, most people expect a six-cylinder engine to have a capacity of at least 2.0-liters, but usually closer to 3.0-liters or more.

Consequently, small-displacement inline-six engines are somewhat rare in the automotive world, and they generate some intrigue when they are produced by auto manufacturers. While many auto manufacturers have used straight-six engines in their vehicles, small displacement engines in this configuration were not always practical or efficient to manufacture on a large scale.

The Displacement of The Smallest Inline-Six

Alfa Romeo was a manufacturer that produced one of the smallest inline-six engines that went into a production car. Alfa introduced the inline-six configuration engines early on in its car manufacturing history. Straight-sixes were used the G1 models produced between 1921 and 1923, and the RL model between 1922 and 1927. However, all these models had larger capacity engines. The engine capacity of the G1 straight-six was 6.0-liters (6,330 cc / 386.3 cu in), while the RL model, Alfa’s first sports model, was powered by engines ranging from 3.0-liters in the RL Normale to 3.6-liters in the RL Targa Florio.

The smallest inline-six engine was the 1500 engine, with a capacity of 1,487 cc or 90.7 cubic-inches that produced 44 horsepower.

This engine was designed for racing since the engine in the RL was considered too heavy for this application. It was first used in the Alfa Romeo P2 Grand Prix car and later in the road version 6C 1500, which was introduced to the motoring public in 1925 and produced between 1927 and 1929.

The Car With The Smallest Inline-6 Engine

The Alfa Romeo 6C models had a wide range of engines. The 6C 1500 was the only model introduced with a small displacement inline-six engine and was in production from 1927 to 1929. The initial model had a single overhead camshaft while the later sport model featured double overhead camshafts.

The small 1500 inline-six engine in the 6C, powered the car to a top speed of 68 MPH, while the DOHC version squeezed an extra 10MPH out of the engine and delivered a blistering top speed of 78 MPH.

Subsequent models in the 6C range were the 6C 1750, 6C 1900, 6C 2300, 6C 2500, and the 6C 3000, which had correspondently larger engines. The last Alfa to feature a straight-six engine was the Alfa Romeo 2600, produced between 1961 and 1969, after which the manufacturer opted to standardize on the V-6 configuration.

Historical Overview of Straight-Six Engines

Inline-six engines are not newcomers to the automobile industry and even outdate the introduction of the V-configuration engines. The early car ICE engines were all in the inline configuration, which led to the speculation that adding more cylinders would give more power.

The First Inline-Six Engine

The first inline-six engine was created back in 1903 by the Dutch manufacturer Spyker. The engine was developed for racing and produced 60 horsepower, setting the trend for auto manufacturers of the day. The additional power produced by the six-cylinder engine was noticed and quickly adopted by the early car manufacturers.

The trend caught on so quickly that by 1909 a large portion of car manufacturers worldwide had adopted the configuration and were producing cars with inline-six engines.

The Benefits Of Inline-Six Engines

Inline-six engines offer numerous benefits that make them still a popular choice among automotive manufacturers today. One of the key advantages of inline-six engines is their inherently balanced design, which results in smoother operation and reduced vibrations compared to engines with fewer cylinders. This balance allows for higher engine speeds and improved performance without sacrificing comfort.

Additionally, inline-six engines typically have a higher torque output across a wider range of engine speeds, making them well-suited for a variety of driving conditions. This torque advantage translates to better acceleration and towing capabilities, making inline-six engines a preferred choice for vehicles such as trucks and SUVs.

Another benefit of inline-six engines is their compact size and efficient packaging. Due to their straight configuration, inline-six engines can be mounted longitudinally in the engine bay, allowing for better weight distribution and easier access to components for maintenance and repairs. This layout also enables smoother airflow and more efficient cooling, contributing to improved overall performance and reliability.

The Popularity Of Inline-Six Engines

Despite facing competition from other engine layouts, the inline-six has maintained a loyal following and continues to be a popular choice in a variety of vehicles. The longer design of the inline-six allows for better weight distribution in the vehicle, contributing to improved handling, stability, and versatility.

This engine configuration, combined with advancements in fuel efficiency and increased environmentally friendly demands, has resulted in its continued use in a wide range of vehicles, from luxury sedans to rugged trucks.

Straight-six or inline-six engines have been popular across a broad spectrum of car manufacturers, with many makers still opting for this engine configuration in many of their current models.

BMW Inline-Six Implementation

BMW is known for its long-standing commitment to the straight-six configuration, and it offers this engine in a variety of models across their lineup. Notable examples include:

• 3 Series (specifically models like the 340i)
• 4 Series
• 5 Series (such as the 540i)
• 7 Series
• X Series SUVs (X3, X4, X5, X6, X7)
• Z4 Roadster

BMW historically created what they claimed to be the lightest inline-six engine to ever be produced. The engine was made in 2005 and included in the BMW 130i intended for the UK market. The engine was constructed of an aluminum and magnesium alloy, which significantly reduced its weight and allowed its inclusion in the construction of smaller vehicles. While this engine may have been the lightest six-cylinder engine, it was certainly not a small displacement engine, with a 3.0-liter capacity.

Other Manufacturers Offering Inline-Six Options

Mercedes-Benz is another luxury brand that utilizes straight-six engines, especially in their newer models equipped with mild hybrid systems for enhanced performance and efficiency.

• CLS 450
• E450 (Sedan, Coupe, Convertible)
• GLE450 SUV
• GLS 450

British car manufacturer Jaguar has reintroduced the straight-six in some of their models, leveraging the engine’s inherent smoothness. Models that offer the inline-six engine include the F-PACE SUV and the XF Sedan.

Land Rover, particularly in the Defender and Range Rover models, has seen the introduction of straight-six engines, replacing V6s in some variants.

• Defender
• Range Rover
• Range Rover Sport

Volvo has historically used straight-six engines, but in recent years, it has seen a shift towards four-cylinder and electric powertrains. However, some older but still modern models feature straight-six engines, such as the XC90.

Hyundai’s luxury brand, Genesis, has begun using straight-six engines in some markets, particularly in their larger sedans and SUVs, such as the Genesis GV80.

These manufacturers and models highlight the diversity of vehicles that employ straight-six engines, ranging from sports cars to luxury sedans and SUVs.

Future Trends Of Small Displacement Inline-Six Engines

The straight-six engine has long been celebrated for its smooth operation, balanced performance, and iconic sound. In recent years, advancements in automotive technology and changing consumer preferences have sparked a renewed interest in this classic engine configuration.

As we look to the future of automotive engineering, there may yet be an application for small displacement inline-six engines, particularly in new-generation green applications. From hybrid powertrains to increased focus on efficiency and performance, the future trends of straight-six engines could potentially deliver exciting innovations and enhancements for drivers around the world.

The future of small displacement inline-six engines looks promising as manufacturers aim to strike a balance between performance and efficiency. With advancements in turbocharging and hybrid technology, smaller inline-six engines are able to deliver impressive power outputs while also improving fuel economy and emissions. This trend is particularly noticeable in the luxury car segment, where automakers are downsizing their engine offerings without compromising on performance or refinement.

The compact size of inline-six engines makes them well-suited for a wide range of vehicle applications. Their inherent smooth operation provides a level of refinement that is difficult to match with other engine configurations. As automakers continue to push the boundaries of engineering and technology, we can potentially see even smaller displacement inline-six engines that offer a compelling combination of power, efficiency, and sophistication, shaping the future of automotive propulsion.