The words "longitudinal" and "transverse" simply describe which way an engine is mounted in a vehicle. Longitudinal engines are arranged with the cylinders running front-to-back. Transverse engines are arranged with the cylinders running side-to-side. Each setup has its own advantages and disadvantages, and they affect everything from the drivetrain to the layout of the cabin.
What Is a Transverse Engine?
A transverse engine is an engine that is mounted so its crankshaft runs perpendicular to the driveshaft and the direction of travel. This means that the engine is also parallel to the axles of the vehicle. If you look under the hood of a car, a transverse engine will have its cylinders arranged left to right. The transverse configuration is the most common layout used in modern cars.
How Does a Transverse Engine Connect to the Drivetrain?
A transverse engine usually connects with the transmission, differential, and axle at the front of the vehicle. That’s why they’re widely used in front-wheel drive cars today. With a transverse layout, it’s also easy to integrate a transaxle. A transaxle is the combination of the transmission, differential, and axle. This direct connection means that fewer parts are needed and less energy is lost.
What Cars Have Transverse Engines?
Most modern cars use a transverse engine layout, especially non-sporty ones. Almost all FWD and AWD vehicles will be transverse, as will most four-cylinder and V6 cars today.
Transverse V8s exist but are very rare. Anything with more than eight cylinders (think supercars) will use a longitudinal layout. Dedicated sports cars will usually be longitudinal, though smaller ones can still use transverse setups.
Transverse Engine Pros and Cons
The transverse setup is popular in everyday cars for its practicality and efficiency. However, size limitations and handling issues make it less ideal for sporty vehicles.
Transverse Engine Pros and Cons
|Transverse Engine Pros||Transverse Engine Cons
|More cabin room
||Limits on power/displacement
|Works well with transaxle/FWD
||Can cause torque steer in FWD cars
|Cheaper and more efficient
Transverse Engine Pros
Efficient Packaging Means More Passenger Space
Because transverse engines tend to be smaller and are mounted side-to-side, they leave more room for the cabin. In FWD cars, there isn’t a need for a transmission tunnel, so the floor can be lower as well. This is especially important in small cars that don’t have much space to spare.
Works Well With FWD
A transverse engine is the perfect complement to a front-wheel drive car. The crankshaft is parallel to the axle, so it can lead right to a transaxle transmission. This keeps the drivetrain components together in one location and requires less material. Additionally, since the majority of the weight is over the driven wheels, the car has better traction. This can be useful in snowy or wet conditions.
Cheap and Efficient
A transverse engine is cheaper to make because of how well it plays with a front-mounted transaxle. There are fewer needed drivetrain parts, meaning it’s lighter and cheaper to make. Plus, it’s a bit more efficient than a longitudinal engine. Because the crankshaft is parallel to the axles, the work put out doesn’t have to be turned 90 degrees.
Transverse Engine Cons
Limits on Power/Engine Size
Because of the size limitations with a transverse engine, you can only get so much displacement and power out of them. Larger engines are tough to package transversely. Although modern turbochargers can help push the performance limit of four-cylinder and six-cylinder engines, they can’t quite match up to a V8. Even if you don’t agree that there’s "no replacement for displacement," a turbo-V8 still beats a turbo-V6.
If you do end up with a high horsepower transverse engine, there can be issues with torque steer. While the engine and transmission being over the driven wheels means lots of traction, too much torque leads to wheel spin and uneven power. This problem is amplified by the unequal driveshafts generally found in transverse setups. The result is the fun yet slightly scary jerking of the steering wheel.
What Is a Longitudinal Engine?
A longitudinal engine is an engine that is mounted so its crankshaft runs parallel to the driveshaft and direction of travel. This means that it is perpendicular to the axles themselves. Longitudinal engines have their cylinders arranged front-to-back. This is a less common layout, and it's usually found in sports cars and 4WD vehicles.
How Does a Longitudinal Engine Connect to the Drivetrain?
A longitudinal engine requires more components to connect to the transmission and axles. Cars with longitudinal engines are usually rear-wheel drive, so the engine must connect to them through the drivetrain. Unlike a transverse layout, the differential and transmission won’t be in front with the engine. The transmission will sit just behind the engine, while the differential will be on the rear axle.
What Cars Have Longitudinal Engines?
Longitudinal engines are most common in rear-wheel drive cars. They’re also common in 4WD SUVs and trucks. Any car with a mid-engine or rear-engine layout is likely to use a longitudinal engine.
For sports cars and supercars, longitudinal engines are often a necessity. Any engine with eight or more cylinders is almost sure to have a longitudinal layout.
Longitudinal Engine Pros and Cons
Longitudinal engines are great for rear-wheel drive sports cars and 4x4s. But the packaging can pose issues for compact everyday vehicles.
Longitudinal Engine Pros and Cons
|Longitudinal Engine Pros||Longitudinal Engine Cons
|Room for more power/displacement
|Better front/rear weight balance
||Impedes cabin room
|More space in engine bay
Longitudinal Engine Pros
Room for Larger Engine
A longitudinal layout is often required to fit a large engine, such as a V8. Cars with large-displacement motors are typically designed for the enthusiast. Because powerful rear-wheel drive vehicles are the most common configuration of high-performance cars, a longitudinal engine makes the most sense. They also work well for the rear differential layout of 4x4 vehicles.
Better Front/Rear Weight Balance
Because a longitudinal engine layout is "North to South," it has a better distribution of weight from front to rear. This improves handling, making it a good choice for performance sports cars.
More Space on Sides of Engine
The layout of a longitudinal engine leaves room on either side of the motor for more components. Specifically, it’s easier to put a turbocharger (or two) in an engine bay with a longitudinal setup. This space also makes the engine easier to work on.
Longitudinal Engine Cons
Since a longitudinal engine can’t lead right into a transaxle, more components are needed to connect to the drivetrain. This means more weight and complexity. Additionally, the work done by the crankshaft must be turned 90 degrees to be sent to the axles. This results in a less efficient setup.
Impedes Cabin Room
The long layout of a longitudinal configuration means there is less physical space for the cabin. Passenger room is typically reduced because the engine has to stretch so far back from the front of the vehicle. The transmission tunnel will also require a higher floor and can reduce center console space.
The long shape and need for a transmission tunnel means that it’s tougher to fit a longitudinal engine in a vehicle. This is especially true if the existing platform was built for transverse motors.
Can You Mount a Transverse Engine Longitudinally?
A transverse engine can be mounted longitudinally. However, doing so as a DIY project would take lots of time and effort. It’s probably been done before, but it doesn’t make much sense.
That doesn’t mean that manufacturers can’t mount the same engine transversely and longitudinally in different cars. A great example is the 2.3 EcoBoost four-cylinder made by Ford. It was used in a transverse setup in the Focus RS, a small hatchback. However, in the Mustang, which was built for a big V8, Ford decided to mount the 2.3 longitudinally. This packaging made more sense for the existing platform.
Which Engine Is Better: Longitudinal or Transverse?
Neither engine layout is inherently better than the other. Most of the time, you're not going to be choosing a vehicle based on whether it's got a longitudinal or transverse engine.
Those who want a "true" sports car experience or a 4x4 will generally lean towards models that have a longitudinal setup. They may be heavier, more expensive, and less practical, but they offer the best enthusiast driving experience and allow for larger displacements and power.
Those who don’t need lots of engine power will generally end up with a transverse setup. They’re cheaper and more efficient, and offer the more practical configuration for most.
Sources: CarThrottle | WhichCar AU