③Riddle of Car Terms - Inline, V-Type, Direct Injection? [Reading Science]

Engine bay of a sports car equipped with a 10-cylinder engine. As the number of cylinders increases, the structure of the engine bay becomes more complex.
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jong-hwa] "The 3.3 gasoline model is equipped with a V-type 6-cylinder engine producing a maximum output of 290 horsepower, befitting A company's 'flagship' model. The 2.5 gasoline model features the newly developed Smartstream G2.5 engine. The Smartstream G2.5 engine optimizes fuel injection by selecting either direct injection (GDi) or indirect injection (MPi) based on speed and revolutions per minute (RPM), injecting fuel in the most efficient way."

This is part of an article introducing newly released cars in Korea. The article includes puzzling automotive terms such as 'V-type 6-cylinder,' 'direct injection (GDi),' and 'indirect injection (MPi).' Before considering the number of engine cylinders, one must first understand the engine displacement.

Engine displacement refers to the volume inside the engine cylinders. Specifically, it denotes the total amount of gas expelled from the cylinder by the movement of the piston. Inside the cylinder, air mixes with fuel and ignites, causing the piston to move. The volume of the space in which the piston moves is called the displacement.

Generally, a larger displacement means the piston moves more, which translates to greater vehicle power. When we say '2000cc displacement,' it means the total volume of gas expelled from the cylinders, or the volume of the space where the piston moves, is 2000cc. Since displacement is a measure that determines engine size and vehicle class, automobile taxes are also levied based on displacement.

Depending on the arrangement of the cylinders, they are classified as horizontally opposed (top photo), inline (middle), and V-type (bottom). This was developed as an idea to efficiently utilize narrow spaces.
[Photo by YouTube screen capture]

Each cylinder contains one piston, and the number of cylinders corresponds to the number of pistons. A 6-cylinder engine means it has six cylinders. However, while more cylinders mean more power, they also consume more fuel. A 4-cylinder engine injects fuel into four places, whereas a 6-cylinder engine must inject fuel into six places.

Why are engines divided into 4-cylinder, 6-cylinder, 8-cylinder, and so on? For example, to build a 1600cc engine cylinder, its size must be larger than a 1.5-liter (ℓ) PET bottle. Making a cylindrical shape that large in a small engine room is difficult, and such a size would likely cause significant vibration and noise.

Therefore, the same total volume is divided into multiple cylinders of the same size. This approach considers engine room space and efficient use of other spaces. For example, the compact 800cc Matiz has 3 cylinders, the 1000cc Morning and 2000cc Sonata have 4 cylinders, and larger engines have 6 or 8 cylinders accordingly.

'V-type' refers to arranging the cylinders in a V shape to save space. Typically, from 6 cylinders upward, three cylinders are placed vertically on each side, meeting at the bottom to form a V shape. When cylinders are arranged side by side in a horizontal line, it is called 'inline,' and when cylinders face each other, it is called 'horizontally opposed.' These names simply describe the shape and have no deeper meaning.

When vehicle specifications are displayed, terms like 'V6,' 'L6,' or 'I6' are used, meaning V-type 6-cylinder or inline (L-type) 6-cylinder engines. The 'In-Line' configuration is abbreviated as I or L.

'Direct injection (GDi)' and 'indirect injection (MPi)' refer to the fuel injection methods. 'GDI (Gasoline Direct Injection)' is the most common gasoline engine method. It injects fuel directly inside the cylinder via an injector to increase combustion power,

while 'MPI (Multi Point Injection)' mixes fuel with air outside the cylinder before injecting it to ignite.

This is a rare sight of a 'V-type 10-cylinder engine.' Since the cylinders cannot be arranged horizontally in a straight line, they are placed in a V shape with five on each side.
[Photo by YouTube screen capture]

GDI offers better fuel efficiency and power but tends to be more expensive and produces more noise and vibration. MPI has lower power and fuel efficiency than GDI but generates less noise and vibration and has better durability.

Therefore, the statement in the article, "The fuel injection method is optimally selected between direct injection (GDi) and indirect injection (MPi) depending on the situation," can be interpreted as "Using GDI during high-speed or acceleration driving and MPI during low-speed or steady driving improves fuel combustion efficiency, i.e., fuel economy."

Understanding these terms beforehand is very helpful when choosing a vehicle. It means you don't have to nod along blindly to the salesperson's fluent but hard-to-understand jargon. At the very least, you can select a suitable vehicle based on the driver's preferences and the car's intended use.

If you prioritize acceleration, a gasoline engine with GDI is preferable; if you value fuel economy, durability, and quietness, choosing a vehicle equipped with the previously introduced engine is better. While you don't need to grasp every detail as a non-expert, knowing the basics such as displacement (which affects taxes), engine type, power, torque, and fuel efficiency is essential.