Car layout

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The layout of a motorised vehicle such as a car is often defined by the location of the engine and drive wheels.

Contents

Layouts can roughly be divided into three categories: front-wheel drive, rear-wheel drive and four-wheel drive. Many different combinations of engine location and driven wheels are found in practice, and the location of each is dependent on the application for which the vehicle will be used.

Front-wheel-drive layouts

FF layout Automotive diagrams 10 En.png
FF layout

Front engine, front-wheel drive

The front-engine, front-wheel-drive layout (abbreviated as FF layout) places both the internal combustion engine and driven wheels at the front of the vehicle. This is the most common layout for cars since the late 20th century. [1] [2]

Mid-engine, front-wheel drive

Some early front-wheel drive cars from the 1930s had the engine located in the middle of the car.

Rear-engine, front-wheel-drive

A rear-engine, front-wheel-drive layout is one in which the engine is between or behind the rear wheels, and drives the front wheels via a driveshaft, the complete reverse of a conventional front-engine, rear-wheel-drive vehicle layout. This layout has only been used on prototype and concept cars.

Rear-wheel drive layouts

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FR layout
MR layout Automotive diagrams 04 En.png
MR layout
RR layout Automotive diagrams 05 En.png
RR layout

Front-engine, rear-wheel drive

The front-engine, rear-wheel drive layout (abbreviated as FR layout) is one where the engine is located at the front of the vehicle and driven wheels are located at the rear. [3] This was the traditional automobile layout for most of the 20th century, and remains the most common layout for rear-wheel drive vehicles. [4]

Mid-engine, rear-wheel drive

The mid-engine, rear-wheel drive layout (abbreviated as MR layout) is one where the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle. This layout is typically chosen for its low moment of inertia and relatively favorable weight distribution.

Rear-engine, rear-wheel drive

The rear-engine, rear-wheel drive layout (abbreviated as RR layout) places both the engine and drive wheels at the rear of the vehicle. In contrast to the MR layout, the center of mass of the engine is between the rear axle and the rear bumper. Although very common in transit buses and coaches due to the elimination of the drive shaft with low-floor bus, this layout has become increasingly rare in passenger cars. The Porsche 911 is notable for its continuous use of the RR layout since 1963.

Four-wheel drive layouts

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F4 layout

Drivetrains where power can be sent to all four wheels are referred to as either four-wheel drive (4WD) or all-wheel drive (AWD). [5]

Front-engine, four-wheel drive

The front-engine, four-wheel drive layout (abbreviated as F4 layout) places the engine at the front of the vehicle and drives all four roadwheels. This layout is typically chosen for better control on many surfaces, and is an important part of rally racing as well as off-road driving.

Most four-wheel-drive layouts are front-engined and are derivatives of earlier front-engine, rear-wheel-drive designs.

Mid-engine, four-wheel drive

The mid-engine, four-wheel drive layout (abbreviated as M4 layout) places the engine in the middle of the vehicle, between both axles and drives all four road wheels.

Although the term "mid-engine" can mean the engine is placed anywhere in the vehicle such that the centre of gravity of the engine lies between the front and rear axles, it is usually used for sports cars and racing cars where the engine is behind the passenger compartment. The motive output is then sent down a shaft to a differential in the centre of the car, which in the case of an M4 layout, distributes power to both front and rear axles.

Rear-engine, four-wheel drive

R4 layout, the engine is located behind the rear axle. Automotive diagrams 06 En.png
R4 layout, the engine is located behind the rear axle.

The rear-engine, four-wheel drive layout (abbreviated as R4) places the engine at the rear of the vehicle, and drives all four wheels.

This layout is typically chosen to improve the traction or the handling of existing vehicle designs using the rear-engine, rear-wheel-drive layout (RR). For example, the Porsche 911 added all-wheel drive to the existing line-up of rear-wheel drive models in 1989.

See also

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Axle Central shaft for a rotating wheel or gear

An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type axle is referred to as a spindle.

Steering System of components that allows vehicles to follow the desired course

Steering is a system of components, linkages, etc. that allows a vehicle to follow a desired course. An exception is the case of rail transport, by which rail tracks combined with railroad switches provide the steering function. The primary purpose of the steering system is to allow the driver to guide the vehicle.

Four-wheel drive Type of drivetrain with four driven wheels

Four-wheel drive, also called 4x4 or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges.

Porsche 996 Fifth generation of the Porsche 911 sports car

The Porsche 996 is the internal designation for the 911 model manufactured from 1997 to 2006 It was replaced by the 997 in 2004 but the high performance Turbo S, GT2 and GT3 variants remained in production until 2006. The 996 had little in common with its predecessor, with the first all new chassis platform since the original 911 and a new water-cooled engine. Technically, it was a major change, a complete breakthrough from the original car other than the overall layout.

Quattro (four-wheel-drive system)

quattro is the sub-brand used by the car brand Audi to indicate that all-wheel drive (AWD) technologies or systems are used on specific models of its Audi automobiles.

Front-engine, front-wheel-drive layout Term used in automotive technology

In automotive design, an FF, or front-engine, front-wheel-drive (FWD) layout places both the internal combustion engine and driven roadwheels at the front of the vehicle.

Rear-engine, rear-wheel-drive layout

In automotive design, an RR, or rear-engine, rear-wheel-drive layout places both the engine and drive wheels at the rear of the vehicle. In contrast to the RMR layout, the center of mass of the engine is between the rear axle and the rear bumper. Although very common in transit buses and coaches due to the elimination of the drive shaft with low-floor buses, this layout has become increasingly rare in passenger cars.

Rear mid-engine, rear-wheel-drive layout Car layout in automotive design

In automotive design, an RMR, or rear mid-engine, rear-wheel-drive layout, is one in which the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle. This layout is typically chosen for its low moment of inertia and relatively favorable weight distribution. The layout has a tendency toward being heavier in the rear than the front, which allows for best balance to be achieved under braking. However, since there is little weight over the front wheels, under acceleration, the front of the car is prone to lift and cause understeer. Most rear-engine layouts have historically been used in smaller vehicles, because the weight of the engine at the rear has an adverse effect on a larger car's handling, making it 'tail-heavy'. It is felt that the low polar inertia is crucial in selection of this layout. The mid-engined layout also uses up central space, making it impractical for any but two-seater sports cars. However, some microvans use this layout, with a small, low engine beneath the loading area. This makes it possible to move the driver right to the front of the vehicle, thus increasing the loading area at the expense of slightly reduced load depth.

Front-engine, rear-wheel-drive layout Automobile layout

In automotive design, a FR, or front-engine, rear-wheel-drive layout is one where the engine is located at the front of the vehicle and driven wheels are located at the rear via a drive shaft. This was the traditional automobile layout for most of the 20th century. Modern designs commonly use the front-engine, front-wheel-drive layout (FF). It is also used in high-floor buses and school buses.

Rear-wheel drive (RWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the rear wheels only. Until the late 20th century, rear-wheel drive was the most common configuration for cars. Most rear-wheel drive vehicles feature a longitudinally-mounted engine at the front of the car.

Transaxle Combined transmission, axle and differential in one assembly.

A transaxle is a single mechanical device which combines the functions of an automobile's transmission, axle, and differential into one integrated assembly. It can be produced in both manual and automatic versions.

A mid-engine layout describes the placement of an automobile engine in front of the rear-wheel axles, but behind the front axle.

Drive shaft Mechanical component for transmitting torque and rotation

A drive shaft, driveshaft, driving shaft, tailshaft, propeller shaft, or Cardan shaft is a component for transmitting mechanical power and torque and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them.

Stout Scarab 1930–1940s American minivan

The Stout Scarab is a streamlined 1930–1940s American car, designed by William Bushnell Stout and manufactured by Stout Engineering Laboratories and later by Stout Motor Car Company of Detroit, Michigan.

Drive wheel

A drive wheel is a wheel of a motor vehicle that transmits force, transforming torque into tractive force from the tires to the road, causing the vehicle to move. The powertrain delivers enough torque to the wheel to overcome stationary forces, resulting in the vehicle moving forwards or backwards.

Front mid-engine, front-wheel-drive layout

In automotive design, a Front Mid-engine, Front-wheel-drive layout is one in which the front road wheels are driven by an internal-combustion engine placed just behind them, in front of the passenger compartment. In contrast to the Front-engine, front-wheel-drive layout (FF), the center of mass of the engine is behind the front axle. This layout is typically chosen for its better weight distribution. Since the differences between the FF and MF layouts are minor, most people consider the MF layout to be the same as the FF layout.

Rear-engine design

In automobile design, a rear-engine design layout places the engine at the rear of the vehicle. The center of gravity of the engine itself is behind the rear axle. This is not to be confused with the center of gravity of the whole vehicle, as an imbalance of such proportions would make it impossible to keep the front wheels on the ground.

Front-engine, four-wheel-drive layout

In automotive design, an F4, or front-engine, four-wheel drive (4WD) layout places the internal combustion engine at the front of the vehicle and drives all four roadwheels. This layout is typically chosen for better control on many surfaces, and is an important part of rally racing, as well as off-road driving. In terms of racing purposes, whether it be on-road or off-road, can be described as followed, "A team that pursues the Weak LS4WD architecture will minimize the development cost of the front-wheel drive system at the expense of having a larger rear powertrain. The Weak architecture produces a vehicle with a large powersplit between the front and rear powertrains, while the Strong architecture recommends a vehicle with more similar power and torque requirements for the front and rear."

Mid-engine, four-wheel-drive layout

In automotive design, an M4, or Mid-engine, Four-wheel-drive layout places the internal combustion engine in the middle of the vehicle, between both axles and drives all four road wheels.

Rear-engine, four-wheel-drive layout

In automotive design, an R4, or Rear-engine, Four-wheel-drive layout places the internal combustion engine at the rear of the vehicle, and drives all four roadwheels.

References

  1. "All About Front-, Rear-, Four- and All-Wheel Drive". www.edmunds.com. Retrieved 18 December 2018.
  2. "All-Wheel Drive vs. Front-Wheel Drive". www.usnews.com. Retrieved 18 December 2018.
  3. "FWD vs. RWD: Which Is Best For You?". www.usnews.com. Retrieved 18 December 2018.
  4. "The Best Wheel Drive For You - Rear Wheel Drive, Front Wheel Drive, Four Wheel Drive, All Wheel Drive". www.kbb.com. Retrieved 18 December 2018.
  5. "Wheel Drive Explained - All-Wheel Drive and More". www.vroomgirls.com. Retrieved 18 December 2018.