Engine placement is one of the most important factors in car design. It can affect the handling, cabin space, cooling requirements and weight distribution of the car. All of this adds up to the cost because of which most of the modern cars are manufactured with a front-engine layout. However, most of the sports car uses a mid-engine layout because of its advantages as well discover later in the story. Front-engine has its limitations when it comes to handling due to which the Chevrolet had to finally shift from a front-engine layout to a mid-engine layout for their C8 Corvette. The Corvette has been front-engine rear-wheel-drive sports car since the late ‘50s and Chevrolet changing the engine layout entirely depicts how important an engine-layout impacts a car. So, what are engine placements and how does engine placements impact the handling?
There is a reason that front-engine layout is commonly used in most cars and that is because it is the most practical. It opens up a ton of cabin space, boot-space and a front-mounted engine is the easiest to work upon and assemble in the factory. Front-engine cars can be fun to drive but then it requires a lot of hard work to develop special types of equipment. For instance, Ford had to come up with a clever electronically controlled limited-slip differential and adaptive dampers so that they can reduce understeer on the Focus ST. And it is not just the Focus ST, front-wheel-drive cars usually tend to have understeer because the front wheels have to steer the car while powering the wheels. If the driver brakes hard or is going very fast and steers the car, the car continues to go in the direction where it was travelling before. Because of the momentum created by the weight at the front of the car, the front tyres slip and the car continues to go straight instead of changing directions.
There is another way of using the front-engine layout which is by powering the rear wheels. While the practicality remains, a lot of the power is wasted in this setup because of the drivetrain loss. The power has to travel through many mechanical components before it reaches the wheels. The power from the engine goes to the gearbox, then to the propeller shaft then to the rear differential and the differential drives the drive shaft which in turn drives the wheels. Because of all this mechanical equipment, a lot of power is wasted when the power is transferred from one part to another. Also, the braking potential is reduced because when the car brakes, the weight of the engine is transferred to the front which increases the momentum in the unwanted direction. This drivetrain combination also limits the acceleration because there is not enough weight on the rear wheels to force them in the ground due to which they can break traction and spin.
A mid-engine layout is mostly used in sports cars because it is the optimum location for the engine. The engine is placed in front of the rear axle to achieve the best possible weight distribution. Because of the optimum weight distribution and the weight of the engine towards the rear axle, it provides additional traction to the tyres. This layout also helps the centre of gravity to be set low in the car so that is can be steered with more precision because there is no additional weight directly on the wheels. The equal weight on all the wheels also increases the stability of the vehicle through the corners. The mid-engine layout also decreases body roll. Usually, the mid-engine layout does not have rear seats for the occupants because there is no space left in the cabin because of the engine. So, it is essentially a two-seater with a parcel shelf which can store some of the luggage.
The rear-engine layout is a rare one. You might have heard the rear-engine layout being used in the Porsche 911 since its first generation. The engine is placed behind the rear axle which means most of its weight is on the rear wheels and that weight forces the wheels into the tarmac. This increases the traction which in turns helps in increasing the acceleration of the car significantly. This layout also increases the braking of the vehicle because under hard braking because of weight transfer. The weight of the engine is shifted on the rear wheels under braking which means it generates the least amount of momentum. The braking efficiency is also increased because not only the front but also the rear tyres are also involved in braking because of the added weight of the engine. In the handling department, the rear-engine layout is tricky to handle because all the weight is at one end of the car. When a car makes a sudden turn it creates a pendulum effect which causes high momentum and resulting in over steering. The rear of the car loses traction and slides out of line causing fishtailing. Over steering is tricky to control and the car can break traction easily especially under rainy season. Because of the rear-engine layout, the cabin space suffers. Yes, you can put on two additional seats for the rear occupants but there is not much space for a full-grown adult to sit comfortably.
These are the three types of engine placements that manufacturer use. It seems an obvious choice for them to use the front-engine layout because it is the most forgiving of the three. Front-wheel drive cars do not need special talent or practice to handle because they are less likely to break traction and go out of control. Also, if the engine is in the front, the manufacturer does not have to worry about special cooling needs of the engine because the engine can suck up air straight from in front. All of the three have their advantages and disadvantages. For the passenger vehicles, the front-wheel-drive seems to be the best choice. For the enthusiasts who crave acceleration, the rear-engine layout seems to do the perfect job. Whereas, the mid-engine layout hits the perfect balance in terms of physics but it comes with its downsides too.