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The R50 program didn't have a happy childhood. Its parents, BMW and Rover, divorced over Mom's spending, and the father (BMW) took custody of the child. Still, the progeny appears to be well-adjusted, safe, and efficient. Note the multiple air bags, composite front module, unique engine mounts, and efficient underhood packaging.

Mini Cooper: Package Delivery

The original Mini, introduced in 1959, brought transverse front- wheel drive to the auto industry, and stayed in production virtually unchanged for 41 years.

The original Mini, introduced in 1959, brought transverse front- wheel drive to the auto industry, and stayed in production virtually unchanged for 41 years. Now there's a new version, built by BMW (it got the baby in its divorce from Rover) in England for export around the world.

Though quite diminutive–142.8-in. overall, or just 23.8-in. longer than a Ford Expedition's wheelbase–the Mini Cooper is packed with technology. For example, the multi-link rear axle–called the "Z-axle"–is borrowed from parent company BMW's 3 Series, as is the plug-and-play multiplex electronics architecture. In addition, the body structure, at 24,500 Nm/degree, is 50% stiffer than a 3 Series. This is due, in part, to the structure's 3,800 spot welds and a one-piece, 8.3-lb., die-cast magnesium cross-car beam. In addition, the Mini Cooper's one-piece hood has the deepest draw of any mass-produced body panel (10.2 in.) currently in production. And the list goes on.

 

Under the hood

Let's start under that deep-draw, tailored-blank hood with its integral headlight buckets. The front fascia attaches to an aluminum bumper beam, which bolts through the composite front end carrier and attaches to the body's longitudinal beams. The carrier module is made of a composite material developed by Owens Corning and DSM Automotive Plastics. It is delivered to the line with the radiator, air conditioning condenser, cooling fan, overflow tank, and shrouding already attached. On a systems basis, BMW claims its price is comparable to a conventional steel structure, and that it can be serviced in the field as a unit.

 The Tritec engine, a 1.6-liter four-cylinder jointly developed by BMW and DaimlerChrysler and built in Brazil, features a cast-iron block, aluminum head, chain-driven overhead cams, and four valves per cylinder with roller tips for reduced friction. The result is 115 hp at 6,000 rpm, and 110 lb.-ft. of torque at 4,500 rpm. The engine meets EU4 emission requirements without secondary air injection or exhaust gas recirculation, thanks to its base design and engine computer.

The powertrain computer (Siemens EMS 2000) controls the electronic throttle, optional CVT automatic transmission, and monitors the engine torque and fuel take-up. If the torque output is below the maximum available, the unit retards ignition timing to increase torque output and improve low-speed performance and drivability. Active Knock Control allows the engine to run on any fuel between 87 and 98 octane, which means one engine map can be used almost anywhere in the world.

Three transmissions are available. The Mini Cooper gets a standard five-speed manual, the Cooper S receives a six-speed Getrag gearbox. A CVT automatic is optional on the Cooper, but unavailable on the more powerful–163-hp–Cooper S. It features full-automatic operation, or semi-automatic shifting through six preset gear ratios.

 

Plug-and-play

The multiplex electrical system connects the engine management, braking, transmission, and instrumentation computers through a CAN-bus, while the body electronics (lighting, windows, door locks, air conditioning, etc.) are connected via a K-bus system. By integrating these systems, as well as the sub-systems on each bus, the engineers were able to reduce the size and weight of the wiring harness, as well as introduce a "plug-and-play" capability: options, like the rain sensor, navigation system, or auto-dimming rear view mirror, can be integrated into the system through simple software changes. Plus, should the need arise, drive-by-wire systems can be added as they come on-line.

 

Passive and active safety

Jack Pitney, general manager of Mini USA, counters concerns about the Mini's safety with this observation: "It has one airbag for every two feet of vehicle." This includes twin front and seat-mounted airbags for the front passengers, and full-vehicle side impact head protection airbags. The front airbags can detect impact strength, and whether or not the passenger seat is occupied, while the head protection airbags remain inflated after the initial crash. Plus, all the airbags use common, interlinked crash sensors to determine optimal inflation strategy.

The Mini also offers ABS, Electronic Brake Distribution (EBD), and Cornering Brake Control (CBC) as standard equipment. Plus, the standard flat tire monitoring system compares the rotational speed of each wheel with its diagonal opposite to determine if a tire is losing pressure.

The EBD system controls front-to-rear brake distribution, shifting braking force to the rear when the vehicle is loaded with people and/or luggage. CBC, on the other hand, increases retardation on the outside front wheel during heavy braking in a corner to counteract oversteer. In addition, it increases rear wheel braking force individually to shorten stopping distances even further. As if this wasn't enough, Dynamic Stability Control (DSC) is available as an option. It reads the lateral and longitudinal forces acting on the car, as well as the driver's steering inputs, then brakes individual wheels and controls the throttle application to keep the car going in the intended direction.

When all else fails, like a severe head-on collision, the entire power-train breaks away from its engine mounts, which transfers energy away from the passenger compartment and through the floor. And the body computer makes certain the battery terminal automatically disconnects, fuel flow is cut off, the doors unlock, and the interior and hazard lights turn on.

 

Steering and brakes

Electric power assist is used on the steering, which eliminates the hydraulic lines, and pump, and provides boost only when needed and at a variable rate. The same unit is used across the line, with programming changes used to alter the assist rate for different wheel, tire, or performance specifications. For greater driver comfort, an additional link in the steering column keeps the wheel nearly vertical, not tilted away from the driver, while equal-length driveshafts quell torque steer.

In addition to the various assist systems already mentioned, the Mini Cooper is fitted with four-wheel disc brakes. The 10.9-in. front discs are ventilated, while the 10.2-in. rear brakes are not, but–between the base Cooper and high-performance Cooper S–only the pad material changes. This dramatically reduces the number of parts that must be catalogued, stored, and sent to the assembly line for installation.

The Mini Cooper, like BMW's 3 Series, has the potential to change perceptions in its market. Though sold as a "premium" small vehicle, the Mini's content, materials, and dynamic abilities may well become the benchmark against which all others are measured. 

 

Numerically Speaking

All measurements are in inches unless otherwise noted.

Cooper
Cooper S
Overall length/width/height
142.8/66.5/55.4
143.9/66.5/55.8
Wheelbase
97.1
97.1
Track front/rear
57.4/57.7
57.2/57.5
Overhang front/rear
24.5/21.1
25.5/21.3
Ground clearance
4.5
4.5
Trunk volume seat up/down (ft.3)
5.6/25.0
5.6/25.0
Unladen weight
2,524 lb.
2,678
Bore/Stroke
3.03/3.37
3.03/3.37
Compression ratio
10.6:1
8.3:1
Horsepower
115 @ 6,000
163 @ 6,000
Torque
110 @ 4,500
155 @ 4,000
Horsepower/ torque per liter
71.9/68.8
101.9/96.9
Tire size
175/65R-15
195/55R-16
Mpg city/highway/combined (est.)
26/43/35
n/a
Assembled in/plant capacity
Oxford, England/100,000 units per year

 

 

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