- Mid-engine design
- 1 Benefits
- 2 Drawbacks
- 3 Variations
- 4 Examples
- 5 References
The mid-engine layout is typically chosen for its relatively favorable weight distribution. The heaviest component is nearer to the center of the vehicle, reducing the vehicle's moment of inertia and making it easier and faster to turn the vehicle to a new direction. Also the engine weight is more evenly carried by all the wheels with this layout. As a result, vehicle stability, traction, and ride quality are naturally improved when turning, braking, and accelerating.
Mounting the engine in the middle instead of the front of the vehicle puts more weight over the rear tires so they have more traction and provide more assistance to the front tires in braking the vehicle, with less chance of rear wheel lockup and less chance of a skid or spin out. If the mid-engine vehicle is also rear-drive (as almost all of them are) the added weight on the rear tires can also improve acceleration on slippery surfaces, providing much of the benefit of all wheel drive without the added weight and expense of all wheel drive components. The mid-engine layout makes ABS brakes and traction control systems work better, by providing them more traction to control. The mid-engine layout may make a vehicle safer, since an accident can occur if a vehicle cannot stay in its own lane around a curve or is unable to stop quickly enough. Mid-engine design is also a way to provide additional empty crush space in the front of the automobile between the bumper and the windshield, which can then be used in a frontal collision to absorb more of the impact force to minimize penetration into the passenger compartment of the vehicle.
In most automobiles, and in sports cars especially, ideal car handling requires balanced traction between the front and rear wheels when cornering in order to maximize the possible speed around curves without sliding out. This balance is harder to achieve when the heavy weight of the engine is located far to the front or far to the rear of the vehicle. Some automobile designs strive to balance the fore and aft weight distribution by other means such as putting the engine in the front and the transmission and battery in the rear of the vehicle. Some of the same benefits are gained, but at the cost of greater moment of inertia compared to the mid-engine layout, making it harder and less responsive to turn the vehicle to a new direction.
Another benefit comes when the heavy mass of the engine is located close to the back of the seats. It makes it easier for the suspension to absorb the force of bumps so the riders feel a smoother ride. But in sports cars the engine position is once again utilized to increase performance and the potentially smoother ride is usually more than offset by stiffer shock absorbers.
This layout also allows the transmission and motor to be directly bolted to each other—with independent suspension on the driven wheels this removes the need for the chassis to transfer engine torque reaction.
The largest drawback of mid-engine cars is restricted rear passenger space; most mid-engine vehicles are two-seat vehicles. The engine in effect pushes the passenger compartment forward towards the front axle (if engine is behind driver). Exceptions typically involve larger vehicles of unusual length or height in which the passengers can share space between the axles with the engine, which can be between them or below them, as in some Toyota vans, large trucks and buses. The mid-engine layout (with a horizontal engine) was common in single-decker buses in the 1950s and 1960s, e.g. the AEC Reliance. The Ferrari Mondial is to date the only successful example of a true mid-engined convertible with seating for 4 and sports car / supercar performance. A version of the Lotus Evora with a removable roof panel is anticipated but no definite date is known.
Like any layout where the engine is not front-mounted and facing the wind, the traditional "engine-behind-the-passengers" layout makes engine cooling more difficult. This has been a problem in some cars such as the Porsche 914, which is air cooled rather than having a front-mounted coolant system. But this issue seems to have been largely solved in newer designs. For example, the Saleen S7 employs large engine-compartment vents on the sides and rear of the bodywork to help dissipate heat from its very high-output engine.
The term "mid-engine" has usually been applied to cars having the engine located between the driver and the rear drive axles. This layout is referred to here as RMR layout. Sports and racing cars typically have this mid-engine layout, as these vehicles' handling characteristics are more important than other features, such as capacity. Additionally the mechanical layout and packaging of a RMR car is substantially different from that of a front engine or rear engine car.
A subset of Front-Rear when the engine is in front of the driver, but fully behind the front axle line, the layout is sometimes called Front Mid engine Rear FMR layout instead of the less-specific term front-engine. In handling and vehicle layout FMR is substantially the same as FR. Some vehicles could be classified as FR or FMR depending on the factory installed engine (I4 vs I6). Historically most classical FR cars such as the Ford Models T and A would qualify as a FMR engine car. Additionally, the difference between FR and FMR may be as little as a few millimeters of engine protrusion in front of the front axle line as manufacturers mount engine as far back in the chassis as possible. Not all manufacturers use the Front-Mid designation.
FMR layout – Front Mid-engine / Rear-wheel drive
These cars are RWD cars with engine placed between driver and front axle. Typically, however, these cars are referred to as FR cars instead.
- Aston Martin Vanquish, DB9 and One-77
- Bentley Continental GT
- BMW Z4 and Z8
- Chevrolet Corvette (second through sixth generations)
- Dodge Viper
- Ferrari 599 GTB Fiorano and 612 Scaglietti
- Honda S2000
- Infiniti G, Infiniti EX, Infiniti M and Infiniti FX
- Lexus LFA
- Mazda MX-5 (third generation), RX-7, and RX-8
- Mercedes-Benz SLR McLaren and SLS AMG
- Nissan 350Z and 370Z
- Suzuki Cappuccino
- Volvo B10M
- Toyota Estima and 2000GT
- Most pre WWII front engine-RWD cars.
FM4 layout – Front Mid-engine / Four-wheel drive
This layout, similar to above FMR layout, with engine between driver and behind front axle, adds front wheel drive to become a four-wheel drive.
- Ferrari FF
- Hummer H1
- Nissan GT-R
- Toyota Previa All-Trac variant
- Toyota Van 4WD variant (first generation)
RMR layout – Rear Mid-engine / Rear-wheel drive
These cars use traditional engine layout between driver and rear drive axle. Typically, they're simply called MR layout cars.
- Toyota MR2
- Pontiac Fiero
- Porsche Cayman
M4 layout – Rear Mid-engine / Four-wheel drive
These cars uses mid-ship, four-wheel drive, with engine between axles.
- Audi R8
- Bugatti Veyron and EB110
- Ford RS200
- Jeep Forward Control
- Lancia Delta S4
- Lamborghini Aventador
- Lamborghini Diablo VT series
- Lamborghini Gallardo
- Lamborghini Murcielago
- Lamborghini Reventon
- MG Metro 6R4
- Panther Solo 2
- Volvo L3314
- Volvo C303
MF layout – Front Mid-engine / Front-wheel drive
These cars are "mid-ship engined" vehicles, but they use front-wheel drive, with engine in front/parallel to driver. Please note that this layout should not be confused with a "front midships" location of the engine, referring to the engine's center of mass being located behind the front axle centerline in which case this would be a FR layout.
- Citroën Traction Avant
- Citroën DS
- Citroën SM
- Cord 810
- Renault 4
- Renault 5
- Renault 16
- Saab Sonett mk1
- Acura Vigor (3rd generation)
- Acura TL only the 2.5 TL
Wikimedia Foundation. 2010.
Look at other dictionaries:
Mid-engine, front-wheel drive layout — MF layout In automotive design, a MF, or 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… … Wikipedia
Mid-engine, four-wheel drive layout — The Lamborghini Murciélago uses the M4 configuration. 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 roadwheels. It is … Wikipedia
Front-engine design — A front mounted engine describes the placement of an automobile engine in front of the vehicle passenger compartment.Historically, this designation was used regardless of whether or not the entire engine was behind the front axle line. In recent… … Wikipedia
Rear mid-engine, rear-wheel drive layout — 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 in front of them, behind the passenger compartment. In contrast to the rear engined RR layout, the center… … Wikipedia
Front mid-engine, rear-wheel drive layout — In automotive design, a FMR, or Front Mid engine, Rear wheel drive layout is one that places the engine in the front, as in the FR layout, but pushed back enough that the engine s center of mass is to the rear of the front axle. This aids in… … Wikipedia
underfloor mid-engine — A design, introduced on the Toyota Previa minivan, where the engine is located below the passenger compartment, between front and rear … Dictionary of automotive terms
Engine balance — is the design, construction and tuning of an engine to run smoothly. Engine balance reduces vibration and other stresses, and may improve the performance, efficiency, cost of ownership and reliability of the engine, as well as reducing the stress … Wikipedia
Mid-lift — (also mid lift) is a design and installation of a Rocker arm on the internal combustion engine, of an Over Head Valve (OHV) design. The MID LIFT principle became known as a term within a US Patent, #4,365,785, issued to Jim Miller in 1982, also… … Wikipedia
Engine control unit — An engine control unit (ECU) is an electronic control unit which controls various aspects of an internal combustion engine s operation. The simplest ECUs control only the quantity of fuel injected into each cylinder each engine cycle. More… … Wikipedia
Mid-American Stock Car Series — 2006 champion James Swan … Wikipedia