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1997 MITSUBISHI MIRAGE HIGHLIGHTS

Engines

While the two Mirage engines are identical in displacement to those available last year, they differ so greatly in detail improvements and overall refinement that it's unfair to call them "carryover" powerplants.

Both the 1.5-liter in DE models and the larger 1.8-liter in LS models feature a cast iron block with an aluminum head, a belt-driven single overhead camshaft (SOHC), roller-type rocker arms and electronically controlled multi-point fuel injection. They differ in that the 1.5-liter 4-cylinder engine has 3 - valves per - cylinder, two intake and one exhaust, while the 1.8-liter has 4-valves-percylinder, with two intake and two exhaust.

And while the horsepower (hp) and torque figures are identical to 1996 – 92 hp and 93 lb-ft for the 1.5-iiter and 113 hp (111 hp with California emission standards) and 116 lb-ft of torque for the 1.8-liter -- the numbers are deceiving. Mitsubishi Motors' engineers have retuned the engines to respond faster and more smoothly in the cut and thrust of daily urban and suburban driving.

By straightening the intake manifold runners on both engines, Mitsubishi Motors' engineers reduced air low resistance, decreasing the engine speed at which maximum horsepower is achieved from 6,000 to 5,500 rpm. Additionally, they increased low-end horsepower and torque. As a result, during those critical first few seconds when the driver steps onto the throttle, Mirage responds more quickly, whether accelerating up a freeway on-ramp, moving away from a stop sign, or zipping along a twisty road. This all adds up to a fun, confidence-inspiring driving experience.

5-Speed Manual

Mitsubishi Motors' engineers spent considerable effort refining the Mirage transmissions as well. Starting with the standard manual 5-speed gearbox, the engineers analyzed each gear ratio to determine the best combination for quick bottom-end response, smooth acceleration, quiet cruising and maximum fuel efficiency. The transmissions were then tailored to each engine, with the 1.5- and 1.8-liter powertrains featuring unique gear ratios.

Quick, smooth shifting adds to the pleasure of operating a manual gearbox, so Mitsubishi Motors' engineers redesigned the synchronizers for even more solid and consistent performance.

The cable shifter also received important refinements. The shifter housing was redesigned for greater stiffness. Also, the shift lever has been changed from a conventional two-shaft design to a more rigid single spherical rotary shaft. Because of these refinements, you'll feel a decided improvement in shift smoothness and precision the first time you shift the lever into gear. 4-Speed Automatic Transmission

Mitsubishi Motors' engineers extensively redesigned the Mirage automatic, an approach that has led to one of the most technically sophisticated and innovative transmissions to be found in any subcompact car.

The 4-speed electronically controlled automatic features adaptive transmission control management system (ATCM) with ECM-TCM technology which allows the transmission to "learn" the owner's typical driving habits and adjust shifting strategies accordingly. ATCM consists of two parts, "comprehensive control optimization," which matches gear selections to the driver's needs under all road conditions, and a learning function, which modifies the timing of gear shifts in response to driver preferences and driving habits.

To achieve the level of precision required, the ATCM system uses what is called a neural network. With a decision-making capability which is patterned after the human brain, this neural network quickly correlates a variety of inputs, including engine power output and brake applications, and instantaneously provides optimum gear shift timing based upon driving style and cargo load.

Most "thinking" automatics are programmed with a specific set of maps representing how a wide range of drivers operate their vehicles. Mitsubishi Motors' engineers took this concept a giant step forward. The Mirage's neural network decision-making capability follows no set schedules. Rather, operates along a continuum, making instant decisions based solely on the driving habits of the person behind the steering wheel...you!

For example, if you drive in a relaxed manner, shifts occur at relatively &127o&127 speeds to enable gentle, economical driving in the higher gears. However, drive enthusiastically, and ATCM holds the transmission in the lower gears to higher engine speeds, for sportier driving.

Or, if you're on a downhill section of road and frequently on the brakes, a ATCM causes downshifts to occur relatively early to provide engine braking. As a result of this sophisticated adaptive control, the Mirage automatic transmission offers smoother shifting and is more responsive to individual driver's needs. It is also more efficient, which directly equates to improved fuel economy and to optimum driver comfort.

Additionally, the transmission and engine computers "talk" to each other. For instance, during upshifts the engine computer slightly retards the ignition timing, reducing engine torque, which results in smoother shifts.

Suspensions

To achieve higher quality ride and handling characteristics, Mitsubishi Motors' improved the fully independent front strut and rear multi-link suspension used on the previous Coupe and Sedan for more nimble handling.

The multi-link design consists of upper and lower lateral arms, a trailing arm and a toe-control link. The toe-control link provides stabilizing toe-in when acted upon by cornering forces. Under such situations, the rear wheels will toein slightly to prevent oversteer or "fishtailing." Al1 models except Coupe DE are equipped with a front stabilizer (anti-roll) bar for reduced body roll and crisper response when cornering. The stabilizer bars on DE and LS models are of different diameters for more precise tuning of each model's ride and handling characteristics.

Steering, Braking

Rack-and-pinion power assisted steering is standard on all Mirage models except Coupe DE, which offers power steering as an option. Requiring only 3.2 turns lock-to-lock, this system provides quick response and a reassuring level of information about the road surface.

Smooth, stable stopping is provided by power-assist front disc and rear drum brakes. The front discs are ventilated for air cooling, which reduces fade under heavy use and improves overall durability. An Anti-lock Braking System (ABS) is optional on LS coupe and sedan models.

Body Structure

Mirage's unit body is constructed to both resist deformation and to deform in a controlled manner. This apparent contradiction results from the fact that in a front or rear impact, deformation of the structure ahead of or behind the passenger compartment absorbs energy, thus reducing the crash energy and the forces reaching the occupants. At the same time, the passenger compartment has been redesigned to be more rigid and unyielding to prevent another vehicle from invading the space occupied by the passengers and for better disbursement of impact energy.

To improve the Mirage's crashworthiness, Mitsubishi Motors' engineers redesigned the body structure after analyzing a variety of computer models. When they were finished, the engineers added stronger front and rear side members for improved side crash protection in the front and rear. In addition, they enlarged the side sills and reinforced the doors to better resist side >impacts. The compact unit body they created has immense structural rigidity. This equates to improved crashworthiness because the unit body and perimeter frame are much more efficient at dispersing shock impact to the side sills, front floor and roof pillars.

The engineers also added a front crossmember to suppress movement of the steering wheel. This member further improves crashworthiness.

The front and rear bumpers also came under the engineers' scrutiny. By designing them to collapse in stages, the vehicle absorbs impacts more efficiently, further reducing the forces reaching the occupants. Environmental Friendly Engineering

In its never-ending battle to preserve limited resources and protect the environment, Mitsubishi Motors has addressed several key issues. To help prevent depletion of the ozone layer, the Mirage air conditioning system uses R134a refrigerant, and non-chlorofluorocarbon (CFC) urethane is specified for the seat padding and steering wheel.

For easier recycling, most plastic parts are made from thermoplastics and stamped with a code indicating their material. Coded plastics make recycling vastly more efficient when a vehicle reaches the end of its service life.

For reduced exhaust emissions, the thickness of the head gasket on both engines has been decreased and the distance between the top ring and the piston crown has been reduced. This decreases the tiny pockets and crevices in the combustion chamber where the air/fuel mixture tends to get trapped and escape combustion. Unburned fuel would otherwise enter the atmosphere as elevated hydrocarbon emissions. These 2-layer metal gaskets are also more resilient, which allows them to expand and contract with the aluminum head and iron block as they heat and cool under use.

The exhaust manifold on the 1.8-liter engine has been changed from cast iron to stainless steel. This more expensive design provides faster catalytic converter light-off during a cold start and thus lower exhaust emissions as well as improved manifold durability and reliability.

Durability/Reliability

Engineering attention to durability, reliability and reduced maintenance make the 1997 Mirage even more enjoyable to own and economical to drive. The stainless steel exhaust manifold on the 1.8-liter engine and redesigned head gaskets for both engines are perfect examples of long-life design.

There are many others. The strength and durability of the timing belt on the 1.5-liter and 1.8-liter engines have been >increased by changes to the core wire and the surrounding rubber. Timing belt durability, in the case of the 1.8-liter engine for example, is enhanced by approximately 15 percent.

New fuel injector nozzles, noted for their small size, light weight and low noise characteristics, have been developed. These injectors also improve hotstarting and are more resistant to developing deposits that can restrict fuel flow.

The 1.8-liter engine has a distributorless ignition system, which eliminates the conventional distributor and ignition on coil, providing more reliable starting and more consistent spark plug firing. This system employs crank angle and cam angle sensors, improving the accuracy with which the spark plugs fire while eliminating the need for periodic ignition timing adjustment.

Refinement

It doesn't matter whether you're driving an expensive luxury sedan or a sporty convertible. Nobody likes a noisy car. Noise leads to irritation and fatigue resulting in an unhappy driving experience. Accordingly, automakers go to enormous lengths to reduce noise and vibration in the vehicles they build.

In the case of the new Mirage, many large and small detail changes add up to significant qualitative and quantitative reductions in noise. The engines in both models are mounted transversely, commonplace in the design of a small front-wheeldrive car in which minimizing overall length and maximizing interior room are prime design considerations. The difference between the 1996 Mirage and the new models is that the engines have been rotated 180 degrees from a west-east to an east-west mounting configuration.

East-west mounting improves engine servicing accessibility and simplifies engine construction, thus reducing costs. Furthermore, and critically from the standpoint of reduced engine vibration, this arrangement reduces the forces resulting from acceleration and deceleration shock loads that can twist the engine and its mounts. This change, in conjunction with new hydraulic engine mounts, helps transform Mirage Coupe and Sedan into two of the most quiet, smooth and refined cars in the subcompact segment.

Noises emanate from a variety of sources in an automobile -- engine, transmission, road, tires -- and Mitsubishi Motors' engineers addressed all of them in methodical fashion. By increasing the gear tooth contact ratio, manual transmission noise was reduced.

The application of damping pads, asphalt sheets, urethane foam and a 4-layer dash insulator results in improved road noise isolation.

The connection between the engine and transmission was made more rigid, and computer aided design (CAD) was employed to reinforce the cylinder block front bulkhead and lower deck to reduce engine noise.

The conventional flywheel was replaced with a flexible flywheel in which the flywheel mass and the crankshaft are dynamically separated by a flexible plate. This arrangement "tunes" the resonant bending frequency (essentially the frequency at which a conventional crankshaft and flywheel would normally vibrate) out of the 200-500 Hertz (cycles per second) range which is particularly irritating to human ears.

Most drivers probably don't give their alternator even a first thought. But Mitsubishi Motors' engineers are certainly familiar with the noise created by the spinning fan blades that cool the alternator. So they redesigned the fan, reducing both ambient and interior noise levels.

Even the oil pan in the 1.8-liter 4-cylinder engine didn't escape the engineers' attention. They redesigned it using low-noise steel plate to reduce exterior noise levels.

Aerodynamics

A quieter, less fatiguing driving experience also results from reduced wind noise. This brings into play the aerodynamic characteristics of the vehicle.

The Mirage's class-leading coefficient of drag (a wind cheating 0.30) results from both obvious and subtle aero details. The low front end and high rear deck are obvious contributors to the efficient design.

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