One thing is true for all petroleum-powered cars: their engines are big, heavy chunks of metal. Engines are what make cars move and they account for a significant portion of a vehicle’s total weight. Automakers must choose whether to mount an engine at the front, middle, or rear of a car. Where it goes makes a big difference in a car’s looks and performance, and benefits and compromises come with each option.
Front-engined cars have engines mounted ahead of the driver over the vehicle’s front axle, and are by far the most common on the road. There are several reasons why this layout is so prevalent. Since most cars are front-wheel drive, it’s simpler to build drivetrains that send power to the wheels they’re closest to. With moving parts contained at the front, designers have more flexibility in how they can build the passenger and cargo areas behind it.
From a performance standpoint, it’s easier to keep the engine supplied with the air it needs to operate, since it faces fresh air as the car moves forward. However, putting the engine’s weight on top of the steering axle isn’t ideal, and can make a car unbalanced. As such, engineers must find ways to keep handling light and prevent pushing through turns.
The mid-engine layout is all about balance, which is why it’s exclusive to performance-oriented machines like the Lamborghini Huracán and Audi R8. They have their engine in the middle between the axles, usually behind the driver. This concentrates mass at the center, enhancing handling and high-speed stability. Plus, with the engine behind the driver, the hood can be shortened and lowered, making it easier to see corner apexes on twisty roads or racetracks.
However, it’s harder to cool the engine when airflow is blocked by the passenger area. Space for passengers and cargo is also compromised. Mid-engined cars are often difficult to maintain too, since the engine is buried deep in the chassis. For these reasons, they’ll likely remain uncommon and expensive to own. Still, nothing can match how they drive.
While most mid-engined cars put the driver in front of the motor, it’s technically possible to have a front-mid engine layout. For example, the Mercedes-Benz SLS AMG’s engine is ahead of the driver but behind the front axle, so it qualifies as front-mid engined — and because of that, the SLS has one of the longest hoods ever made.
The rear-engine layout is rare, since putting the engine behind or on top of a car’s rear axle makes little engineering sense — but logic and fun aren’t always corollaries. Certainly the most famous rear-engined car is the Porsche 911, which embraces and enhances the unique quirks that come with this layout.
Unusual driving characteristics are rear engined cars’ prime feature. Weighing down the rear axle by putting the engine over it aids traction when accelerating from a stop or out of a corner. It also sharpens handling, since there’s not as much weight on the steering axle. However, hitting the brakes shifts weight forward, so rear-engined cars are more prone to pirouette into a slide or spinout. Some say this makes them difficult to control, while others relish the challenge of wrangling an inherently unstable beast.
Regarding practicality, rear-engined, rear-wheel drive cars theoretically have similar packaging benefits as front-engined, front-wheel drive cars: the rest of the vehicle can be devoted to passengers or cargo. But given consumers’ unfamiliarity with them and their potentially sketchy handling, rear-engined cars won’t take over roadways any time soon. Fortunately, the 911 is there to show how following convention isn’t always the path to success.