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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 past 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.

Automotive diagrams 05 En

Rear-engine position / Rear-wheel drive

Rear-engined cars are almost always rear wheel drive, a layout known as RR. The exception is certain high performance four wheel drive models from some European automakers. This layout is chosen for three reasons - packaging, traction, and ease of manufacture:

  • Since the engine is located at an extremity, the rest of the vehicle can be used for passengers and luggage.
  • Having the engine located over the driven wheels increase downward pressure which is helpful for grip on loose surfaces.
  • The drivetrain can be assembled as a unit and installed easily at the factory - easier than a front wheel drive layout where the driven wheels also steer the car.
Hilman Imp - SCT 706J at Belvoir 08 - DSC01190

Hillman Imp

The disadvantage of the rear engine configuration, is that placing the engine outside the wheelbase can create problems for car handling[citation (source) needed]as, when the car begins to slide on a corner, the end of the car will tend to want to swing wide and overtake the front — especially under braking. This tendency is referred to as oversteer and creates potential safety issues both for ordinary drivers, and even in racing applications. There are also occasions where expert drivers find such behavior desirable in drifting[citation (source) needed], a motorsport based on intentional oversteer. Details on the handling characteristics of rear-engined cars were prominently featured in the 1965 book Unsafe at Any Speed.

In addition, even though the rear wheels benefit from the additional traction the added weight of the engine gives, the front wheels still need traction in order to steer the car effectively. For this reason, a rear-engined car can also be prone to understeer.

Although this layout was once popular, it was mainly found in small, inexpensive cars and light commercials, most car makers have abandoned the rear-engined layout apart from Porsche who has gradually developed their design with improvements to the suspension and chassis to reduce the shortcomings of the layout to exceptional levels in road and race cars.[citation (source) needed]

The most popular current applicaton of this layout is in Low-floor buses where its spacesaving attributes are best applied.

On the De Lorean, to compensate for the uneven (35/65) weight distribution caused by the rear-mounted engine, the car had rear wheels with a diameter slightly greater than the front wheels.

Some rear-engined carsEdit

DeLorean - 83 DMC at Sandbach 08 - P4170146

De Lorean gullwinged sports car

Smart Fortwo

Smart Fortwo's three-cylinder engine officially sits behind the rear axle.

ReferencesEdit


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