In automotive design layout is the place where both the engine and driven wheels are. An engine is a mechanical device that produces some form of output from a given input

Contents 1 Types 2 Characteristics 3 Advantages of front-wheel drive 4 Disadvantages of front-wheel drive 5 References

Types

Front-engine, front-wheel drive, layout places both the engine and driven wheels at the front of the vehicle. A front-mounted engine describes the placement of an Automobile engine in front of the vehicle passenger compartment Front-wheel drive (or FF layout) is a form of engine / transmission layout used in Motor vehicles where the engine drives the front Wheels An engine is a mechanical device that produces some form of output from a given input This layout is typically chosen for its compact packaging - that is, it takes up very little space, allowing the rest of the vehicle to be designed more flexibly. In contrast with the FR layout, the FF layout eliminates the need for a central tunnel or a higher chassis clearance to accommodate a driveshaft providing power to the rear wheels. Like the RR and RMR layouts, it places the heavy engine over the drive wheels which aids traction. In Automotive design, a RR, or Rear-engine, Rear-wheel drive layout is one which places both the engine and drive wheels at the rear In Automotive design, a RMR or Rear Mid-engine, Rear-wheel drive layout is one in which the rear wheels are driven by an engine placed just As the steered wheels are also the driven wheels, FF cars are generally considered superior to FR cars in conditions such as snow, mud or wet tarmac. However, powerful cars rarely use the FF layout because weight transference under acceleration unloads the front wheels and sharply reduces their grip, effectively putting a cap on the amount of horsepower which could realistically be utilized. Electronic traction control can avoid wheelspin but largely negates the benefit of extra mileage.

Characteristics

Front wheel drive gives more interior space since the powertrain is a single unit contained in the engine compartment of the vehicle, there is no need to devote interior space for a driveshaft tunnel or rear differential, increasing the volume available for passengers and cargo. For the UK engine manufacturer see Powertrain Ltd. In a Motor vehicle, the term drivetrain, powertrain or powerplant ^[1] There are some exceptions to this as rear engine designs do not take away interior space. In Automobile design, a rear-engine design layout places the Engine at the rear of the vehicle (See Porsche 911, and Volkswagen Beetle) It also has fewer components overall and thus lower weight. The Porsche 911 (pronounced as Nine Eleven, Neunelfer is a Sports car made by Porsche AG of Stuttgart, Germany The Volkswagen Beetle, officially known as the type 1 and originally called ‘Käfer’ is an Economy car produced by the German auto maker Volkswagen ^[1] The direct connection between engine and transaxle reduce the mass and mechanical inertia of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economy. The vis insita or innate force of matter is a power of resisting by which every body as much as in it lies endeavors to preserve in its present state whether it be of rest or of moving Fuel economy in automobiles is the amount of Fuel required to move the Automobile over a given Distance. ^[1] In front wheel drive cars the mass of the drivetrain is placed over the driven wheels and thus moves the centre of gravity farther forward than a comparable rear-wheel drive layout, improving traction and directional stability on wet, snowy, or icy surfaces. Traction refers to the Friction between a drive member and the surface it moves upon where the friction is used to provide motion ^[1][2][3] Front-wheel drive cars, with a front weight bias, tend to understeer at the limit, which according to for instance SAAB engineer Gunnar Larsson is easier since it makes instinct correct in avoiding terminal oversteer, and less prone to result in fishtailing or a spin. Understeer is a term for a Car handling condition in which during cornering the circular path of the Vehicle 's motion is of a greater radius than the circle indicated Oversteer is a phenomenon that can occur in an Automobile which is attempting to turn Fishtailing (also called " tank slapping " is a car handling problem which occurs in Rear wheel drive vehicles when too much power is applied for the driving ^[3][4]

According to a sales brochure for the 1989 Lotus Elan, the ride and handling engineers at Lotus found that "for a given vehicle weight, power and tire size, a front wheel drive car was always faster over a given section of road. Lotus Elan is the name of two Convertible Cars and one fixed head Coupé produced by Lotus Cars. Lotus Cars is a British manufacturer of sports and racing cars based at Hethel, Norfolk, England. "^[5] However, this may only apply for cars with moderate power-to-weight ratio. ^[2][6][7] According to road test with two Dodge Daytonas, one FWD and one RWD, the road layout is also important for what configuration is the fastest. This page is about the 1980s and 1990s Daytona For information on the Charger Daytona, see this page. ^[3]

In a front wheel drive car it is easier to correct trailing-throttle or trailing-brake oversteer. Lift-off oversteer (also known as snap-oversteer, trailing-throttle oversteer, throttle off oversteer, or lift-throttle oversteer) is a form ^[3]

Some high power front wheel drive cars may exhibit torque steer. Torque steering is the influence of the engine torque on the Steering for some Front-wheel drive vehicles Torque steer can be addressed by using a longitudal layout, equal length drive shafts, half shafts, a multilink suspension or centre-point steering geometry. ^{[8][9][10][11][12][13][14][15]}

Lack of weight shifting will limit the acceleration of a front-wheel drive vehicle. During heavy acceleration, weight is placed on the rear, or driving wheels, which improves traction. This is the main reason why nearly all racing cars are rear-wheel drive. However, since front-wheel drive cars have the weight of the engine over the driving wheels, the problem only applies in extreme conditions. The weight shifting and weight distribution of rear wheel drive cars cause oversteer and the related problem of fishtailing. Oversteer is a phenomenon that can occur in an Automobile which is attempting to turn Fishtailing (also called " tank slapping " is a car handling problem which occurs in Rear wheel drive vehicles when too much power is applied for the driving On snow, ice, and sand, rear-wheel drive loses its traction advantage to front or all-wheel drive vehicles which have greater weight on the driven wheels. Rear wheel drive cars with rear engine or mid engine configuration do not suffer from this, although fishtailing remains an issue. In Automobile design, a rear-engine design layout places the Engine at the rear of the vehicle A mid-engine layout describes the placement of an Automobile engine between the rear and front axles Some rear engine cars (e. g. Porsche 911) can suffer from reduced steering ability under heavy acceleration, because the engine is outside the wheelbase and at the opposite end of the car from the wheels doing the steering although this configuration provides outstanding grip and traction as the engine weight is over the drive wheels. The Porsche 911 (pronounced as Nine Eleven, Neunelfer is a Sports car made by Porsche AG of Stuttgart, Germany A rear wheel drive car's center of gravity is shifted rearward when heavily loaded with passengers or cargo, which may cause unpredictable handling behavior. ^[4]

On FR cars the long driveshaft adds to drivetrain elasticity. ^[4]

Advantages of front-wheel drive

• Interior space: Since the powertrain is a single unit contained in the engine compartment of the vehicle, there is no need to devote interior space for a driveshaft tunnel or rear differential, increasing the volume available for passengers and cargo. For the UK engine manufacturer see Powertrain Ltd. In a Motor vehicle, the term drivetrain, powertrain or powerplant ^[1]
  • However, the exhaust pipes can now be routed through the unused space once occupied by the drive train.
• Cost: Fewer components overall. ^[1]
• Weight: Fewer components usually means lower weight.
• Improved fuel efficiency due to less weight. Fuel efficiency, in its basic sense is the same as Thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier
• Improved drivetrain efficiency: the direct connection between engine and transaxle reduce the mass and mechanical inertia of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economy. The vis insita or innate force of matter is a power of resisting by which every body as much as in it lies endeavors to preserve in its present state whether it be of rest or of moving Fuel economy in automobiles is the amount of Fuel required to move the Automobile over a given Distance. ^[1]
• Assembly efficiency: the powertrain can often be assembled and installed as a unit, which allows more efficient production.
• Placing the mass of the drivetrain over the driven wheels moves the centre of gravity farther forward than a comparable rear-wheel drive layout, improving traction and directional stability on wet, snowy, or icy surfaces. Traction refers to the Friction between a drive member and the surface it moves upon where the friction is used to provide motion ^[1][2][3]
• Predictable handling characteristics: front-wheel drive cars, with a front weight bias, tend to understeer at the limit, which according to for instance SAAB engineer Gunnar Larsson is easier since it makes instinct correct in avoiding terminal oversteer, and less prone to result in fishtailing or a spin. Understeer is a term for a Car handling condition in which during cornering the circular path of the Vehicle 's motion is of a greater radius than the circle indicated Oversteer is a phenomenon that can occur in an Automobile which is attempting to turn Fishtailing (also called " tank slapping " is a car handling problem which occurs in Rear wheel drive vehicles when too much power is applied for the driving ^[3][4]
• The driver can control the movement of the car even while skidding by steering, throttling and pulling the hand brake (given that the hand brake operates the rear wheels as in most cases, with early Saabs being an exception). ^[16]
• According to a sales brochure for the 1989 Lotus Elan, the ride and handling engineers at Lotus found that "for a given vehicle weight, power and tire size, a front wheel drive car was always faster over a given section of road. Lotus Elan is the name of two Convertible Cars and one fixed head Coupé produced by Lotus Cars. Lotus Cars is a British manufacturer of sports and racing cars based at Hethel, Norfolk, England. "^[17] However, this may only apply for cars with moderate power-to-weight ratio. ^[2][18][7] According to road test with two Dodge Daytonas, one FWD and one RWD, the road layout is also important for what configuration is the fastest. This page is about the 1980s and 1990s Daytona For information on the Charger Daytona, see this page. ^[3]
• It is easier to correct trailing-throttle or trailing-brake oversteer. Lift-off oversteer (also known as snap-oversteer, trailing-throttle oversteer, throttle off oversteer, or lift-throttle oversteer) is a form ^[3]
• The wheelbase can be extended without building a longer driveshaft (as with rear wheel driven cars).

Disadvantages of front-wheel drive

• Torque steer is the tendency for some high power front-wheel drive cars to pull to the left or right under hard acceleration. Torque steering is the influence of the engine torque on the Steering for some Front-wheel drive vehicles It is a result of the offset between the point about which the wheel steers (which falls at a point which is aligned with the points at which the wheel is connected to the steering mechanisms) and the centroid of its contact patch. Contact patch is the portion of a vehicle's Tire that is in actual contact with the road surface The tractive force acts through the centroid of the contact patch, and the offset of the steering point means that a turning moment about the axis of steering is generated. In an ideal situation, the left and right wheels would generate equal and opposite moments, cancelling each other out, however in reality this is less likely to happen. Torque steer can be addressed by using a longitudinal layout, equal length drive shafts, half shafts, a multilink suspension or centre-point steering geometry. ^{[19][20][21][22][23][24][25][26]}
• Lack of weight shifting will limit the acceleration of a front-wheel drive vehicle. In a vehicle, the weight shifts back during acceleration, giving more traction to the rear wheels. This is one of the main reasons why nearly all racing cars are all- or rear-wheel drive. However, since front-wheel drive cars have the weight of the engine over the driving wheels, the problem only applies in extreme conditions.
• In some towing situations, front-wheel drive cars can be at a traction disadvantage since there will be less weight on the driving wheels. Because of this, the weight that the vehicle is rated to safely tow is likely to be less than that of a rear-wheel drive or four-wheel drive vehicle of the same size and power.
• Traction can be reduced while attempting to climb a slope in slippery conditions such as snow or ice covered roadways.
• Due to geometry and packaging constraints, the CV joints (constant-velocity joints) attached to the wheel hub have a tendency to wear out much earlier than the universal joints typically used in their rear-wheel drive counterparts (although rear-wheel drive vehicles with independent rear suspension also employ CV joints and half-shafts). Constant-velocity joints (aka homokinetic or CV joints) allow a rotating shaft to transmit power through A universal joint, U joint, Cardan joint, Hardy- Spicer joint, or Hooke's joint is a Independent suspension is a broad term for any Automobile suspension system that allows each wheel on the same Axle to move vertically (i The significantly shorter drive axles on a front-wheel drive car causes the joint to flex through a much wider degree of motion, compounded by additional stress and angles of steering, while the CV joints of a rear wheel drive car regularly see angles and wear of less than half that of front wheel drive vehicles.
• The driveshafts may limit the amount by which the front wheels can turn, thus it may increase the turning circle of a front-wheel drive car compared to a rear-wheel drive one with the same wheelbase.

References

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