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2008 Mitsubishi Outlander Offers Choice Between V-6 And New I-4 Power

2008 Mitsubishi OutlanderThe next-generation Mitsubishi Outlander, which was introduced for 2007 exclusively powered by a new 220-hp V-6 engine, for 2008 offers a a new 2.4-liter DOHC MIVEC 4-cylinder engine. The 4-cylinder engine is featured in the revised Outlander ES model and new Special Edition model to provide a new choice for customers who prioritize fuel economy over maximum performance.

The V-6, which produces 213 hp in PZEV spec, continues in the LS and XLS models with a 6-speed Sportronic automatic transmission. The XLS features magnesium steering wheel paddle shifters. The Outlander ES model comes equipped as standard with a new Sportronic® continuously variable transmission (CVT). The V-6 and 4-cylinder models are available with 2WD or 4WD.

The combination of the 4-cylinder engine, CVT, aluminum roof panel (also on V6 models) and a modified rear suspension system all contribute to fuel economy in the Outlander ES and Special Edition.

The new 2.4-liter 4-cylinder engine is based on the same architecture as the 2.0-liter engine used in the next-generation Lancer. The Outlander’s 2.4-liter version produces 168 hp and 167 lb.-ft. of peak torque. Counter-balance shafts, a system patented by Mitsubishi over 30 years ago to reduce engine vibration and noise, help give the Outlander ES and Special Edition smooth, quiet performance, a trait further enhanced by the CVT. The Mitsubishi Innovative Valve-timing Electronic Control (MIVEC) system for the DOHC engine controls valve timing on both the intake and exhaust camshafts to optimize performance at all engine speeds.
The new Outlander 2.4-liter MIVEC engine has a 10.5:1 compression ratio and still uses regular-grade fuel (87 AKI). The engine has a free-revving character (6,500 rpm redline), and an optimal balance of linear power delivery and wide torque curve that gives Outlander responsive and flexible responses.

Using a timing chain instead of a belt allows for a more compact design and also helps ensure reliability. Iridium spark plugs contribute to lower emissions and help extend major service intervals for lower cost of ownership.

The exhaust manifold’s rear location on the transverse engine yields important benefits, including optimal packaging of the catalysts for quicker “light off,” and therefore better emissions performance. The manifold’s location also contributes to the vehicle’s excellent weight distribution, which is 55/45 in the 4WD model, for responsive handling.

V-6 Provides Abundant Torque
The Outlander LS and XLS models’ 4-valve-per-cylinder V-6 produces 220 hp at 6,250 rpm (213 hp, PZEV) and 204 lb.-ft. of peak torque at 4,000 rpm, running on recommended regular-grade fuel. A combination of the Mitsubishi Innovative Valve Timing and lift Electronic Control (MIVEC) – a variable valve timing and lift system – and a two-stage variable intake manifold ensure a broad torque curve. The Outlander V-6 provides nearly 90 percent of peak torque from just 2,000 rpm. Combined with the optimized ratios of the six-speed automatic transmission, this performance curve gives the new Outlander outstanding response in all driving situations. The Mitsubishi V-6 engine uses aluminum for its cylinder block, cylinder heads, oil pan, and resin rocker covers and weighs just 341.7 lbs.

California P-ZEV Certification
The Outlander V-6 is designed and optimized to meet the most stringent emissions requirements – it was the first V-6 in the U.S. market to offer P-ZEV certification in states where applicable. The engine uses efficient, clamshell-type exhaust manifolds. A catalytic converter housed within the clamshell of each manifold helps improve exhaust emissions performance, particularly under cold start conditions.

The combination of a high-efficiency HC-trap catalyst system and PremAir® Direct Ozone Reduction catalyst radiator helped earn the new Outlander Partial Zero Emissions Vehicle (PZEV) certification in California, making Outlander the first PZEV V-6 in the segment. The PremAir® catalyst radiator effectively reduces ozone in the air that passes over its coated surfaces by converting ozone molecules into oxygen molecules upon contact. Tests have shown that PremAir® catalyst radiator converts as much as 80 percent of the ozone it contacts into oxygen. Federal certification is Tier 2 bin 5.

A sophisticated electronically controlled multi-point fuel injection system ensures precision fuel delivery. The electronic throttle control system (throttle-by-wire) eliminates the mechanical linkage between the accelerator pedal and the throttle plate. Looping the fuel line around the engine improves exhaust gas performance by reducing fuel temperature differences between the delivery pipes, reducing pulsations within the delivery pipes, and suppressing variations in the amount of fuel injected.

Mitsubishi’s environmental commitment goes well beyond vehicle emissions. Mitsubishi made a concerted effort to substantially reduce or eliminate toxic substances used in vehicle manufacture. For example, the fuel tank is free of hexavalent chromium and lead.

Mitsubishi Innovative Valve Timing and lift Electronic Control system (MIVEC)
Many engines today employ some form of variable valve control system, which can optimize power and torque by varying valve opening times and/or duration. Some of these valve control systems optimize performance at low and mid-range engine speeds. Others focus on enhancing only high-rpm power.

In the Outlander V-6 engine, the Mitsubishi Innovative Valve Timing and lift Electronic Control (MIVEC) system provides both of these benefits by controlling valve timing and lift. Despite its technological complexity, the basic operation of the MIVEC system can be expressed quite simply: MIVEC alters the cam profiles, tailoring engine performance in response to driver input.
In essence, MIVEC serves the same function as “swapping cams,” something that car enthusiasts and racers might do when modifying older-design engines to produce more power. However, such swaps come with a compromise – generally yielding either greater low-end torque or more high-end horsepower, but not both.

MIVEC achieves both goals. With MIVEC, the “cam swap” occurs automatically at 4,750 rpm. The cam switch operation is transparent to the driver, who is simply rewarded with a smooth flow of power.

Under low-rev conditions, MIVEC uses a smaller cam profile, yielding medium lift on the intake valves to provide stable idle and lower emissions. When engine speed reaches the switchover point, MIVEC applies longer duration and higher lift to the intake valves, yielding maximum and efficient power and torque over a broad engine speed range.

How MIVEC Works
In the MIVEC system, two distinct cam profiles are used to provide two engine modes: a low-speed mode, consisting of low-lift cam profiles; and a high-speed mode. The low-lift cams and rocker arms – which drive separate intake valves – are positioned on either side of a centrally located high-lift cam.

Each of the intake valves is operated by a low-lift cam and rocker arm, while placing a T-lever between them allows the valves to follow the action of the high-lift cam. At low speeds, The T-lever’s wing section floats freely, enabling the low-lift cams to operate the valves. The intake rocker arms contain internal pistons, which are retained by springs in a lowered position while the engine speed is below the MIVEC switchover point, to avoid contacting the high-lift T-shaped levers. At high speeds, hydraulic pressure elevates the hydraulic pistons, causing the T-lever to push against the rocker arm, which in turn makes the high-lift cam operate the valves.

In summary, MIVEC switches to the higher cam profile as engine speed increases, and drops back to the lower cam profile as engine speed decreases. The reduced valve overlap in low-speed mode provides stable idling, while accelerated timing of the intake valve’s closing reduces backflow to improve volumetric efficiency, which helps increase engine output as well as reduce lift friction. High-speed mode takes advantage of the pulsating intake effect created by the mode’s high lift and retarded timing of intake valve closure. The resulting reduced pumping loss of the larger valve overlap yields higher power output and a reduction in friction. The low- and high-speed modes overlap for a brief period, boosting torque.

2.4-Liter Engine Uses Its Own MIVEC System
In the Outlander 2.4’s MIVEC system, intake and exhaust cam timing is independently controlled to provide four optimized engine-operating modes:

  • Under most conditions, to ensure highest fuel efficiency, valve overlap is increased to reduce pumping losses. The exhaust valve opening timing is retarded for higher expansion ratio, enhancing fuel economy.
  • When maximum power is demanded (high engine speed and load), intake valve closing timing is retarded to synchronize the intake air pulsations for larger air volume.
  • Under low-speed, high load, MIVEC ensures optimal torque delivery with the intake valve closing timing advanced to ensure sufficient air volume. At the same time, the exhaust valve opening timing is retarded to provide a higher expansion ratio and improved efficiency).
  • At idle, valve overlap is eliminated to stabilize combustion.

V-6 Variable Intake Manifold
Like variable valve timing, variable intake manifolds are a modern interpretation of an idea first used in high-performance engines decades ago. So-called “long-ram” manifolds were once used to provide a longer intake tract, which helped to boost low-end and mid-range torque. In contrast, “short-ram” manifolds helped boost high-end horsepower, but usually at the expense of low-end and mid-range torque. The Mitsubishi 6B31 V-6 engine’s aluminum intake manifold uses a resin Induction Control Valve to provide the benefits of short and long intake tracts, automatically switching in response to engine speed. A flap inside the Induction Control Valve remains closed below 3,600 rpm, forcing the intake charge to take a longer route to the inlet valves. Over 3,600 rpm, the flap opens, providing a shorter tract to the valves to increase power. Positioning the EGR distribution inlet on the upper intake manifold, far from the throttle valve, improves real-world fuel consumption by lowering the temperature entering the EGR distribution passageway.

Premium Level Refinement
When setting standards for minimizing noise, vibration and harshness (NVH), Mitsubishi benchmarked not only Outlander competitors, but premium-level models, as well. The 60-degree V-6, an inherently smooth-running configuration, does not require a balance shaft, yet engineers took extra steps to quell sources of even the smallest vibrations. One example is offsetting the cylinder axis of rotation in the direction of crank rotation, which reduces operating friction.

For the air intake, lengthened ducts and optimized resonators ensure quietness and to reduce weight. A variable-valve main muffler helps reduce noise and vibration. Even reducing the number of exhaust system hangers from six on the previous model to four on the new one helps reduce a source of vibration transmission.

The Outlander V-6 mounts to the front subframe using a four-point inertial axis system with liquid-filled mounts that help to reduce vibration and enhance ride quality. The pressure-cast aluminum right mounting bracket (engine side) and left mounting bracket (transmission side) have both been made more rigid and lighter, which helps to reduce acceleration noise. A new insulator design for the front and rear mounts is specially tuned for use with the six-speed automatic transmission, offering a optimal balance of insulation from idle vibration and acceleration shock.

Small Details for Enhanced Durability
Mitsubishi took several steps to enhance engine durability, as well. One example is the use of long-reach Iridium spark plugs. The thinner diameter plug (M12) allows wider valve diameter, and enlarging the water jacket improves cylinder head cooling performance. Another example is the 100,000-mile timing belt, which is quieter than a chain while providing outstanding durability.

The Outlander’s cooling system also provided opportunities to reduce parts and weight while enhancing overall performance and durability. The cross-flow radiator is lower than a conventional type, and therefore easier to install and remove if needed. The radiator is installed with one-touch clamps rather than bolts, improving serviceability. The number of parts in the blower and condenser connections was reduced.

Six-Speed Sportronic® Automatic Transmission
The new Outlander V-6 is teamed exclusively to a six-speed Sportronic automatic transmission, which features a sport mode. As with the new outlander V-6 engine, the new six-speed transmission was designed to impart the refinement expected in premium class vehicles.

Employing six gear ratios instead of five – as most competitors do – helps make the transmission more responsive to a wider variety of driving conditions. In particular, “hunting” between gears over varying road grades is minimized.

Advanced control of the engine and transmission minimizes torque fluctuation during gear changes. The INVECS-II electronic controls match automatic gear changes to both road conditions and individual driving habits. The shift schedule is optimized to match expectations of the average driver, and the transmission responds to driver input and adapts to an individual driver’s style.

Sport Mode enables driver to enjoy more dynamic driving performance by shifting manually. The driver can shift gears manually using the floor console shift handle (forward for upshifts and rearward for downshifts), or a feature more commonly seen on exotic sports cars – and a first for the compact SUV segment – magnesium Sportronic steering wheel paddle shifters in Outlander XLS models. The right-hand shift paddle is for up-shifting, and the left-hand paddle is for downshifts.

The paddles are attached to the steering column and remain in the same position regardless of the steering wheel angle for ease of shifting even in tight corners. The paddle shifters are active during sport mode and automatic mode to enable quick manual shifting at any time. The Outlander can be driven away in second gear under slippery road conditions.

Outlander 2.4 CVT Delivers Excellent Performance and Economy
The Outlander is one of the few crossover SUVs to offer a continuously variable transmission (CVT) in place of a conventional automatic transmission. A CVT not only can enhance performance and fuel economy, but also provides a smoother driving experience than a traditional automatic. As a result, the driver will enjoy a more premium driving experience.

A conventional automatic transmission uses fixed gear ratios, which engineers must select to provide the optimal balance of performance and efficiency and suit all customers and driving conditions. A CVT, in contrast, operates on a pulley system that allows an infinite variability between highest and lowest available ratios with no discrete steps or shifts. A CVT smoothly adapts to changing vehicle speeds, allowing the engine speed to remain at its level of peak efficiency, helping to improve both fuel economy and exhaust emissions. Because a CVT does not “shift” gears, the customer also benefits from smoother performance.

The Outlander ES model’s CVT’s ratio range is 2.349 to 0.394, with a 6.12 final drive. The transmission ratio is always adapting to the driver’s current power needs and the driving conditions.

CVT Control Modes
The Outlander ES model’s CVT provides a P-R-N-D-DS shift quadrant, with DS engaging instantaneous 6-step manual control via the console-mounted shifter. The Outlander Special Edition in addition includes the magnesium steering wheel paddle shifters from the XLS model. Many conventional automatic transmissions offer manual control to provide a more engaging driving experience. The Sportronic CVT’s pulley hydraulics, however, offer faster and crisper “shifts” than in conventional automatics. Such programming would theoretically have allowed Mitsubishi to select any number of “gears,” but six was determined as the best number for ease of use, sporty driving and flexible performance.

In D mode (analogous to the “Drive” mode in a conventional automatic), the CVT ratio is controlled based on shift patterns, with a target primary rotation speed set to match vehicle speed and throttle opening. The D-range ratio pattern is programmed to provide an optimal balance of dynamic performance and fuel economy on most roads.

For slope control, INVECS III software determines the excess or deficiency of engine braking from the driver’s brake and accelerator operation, based on a value that suits driving conditions, and adaptively compensates. In particularly hilly areas, the driver can select “L” mode to provide stronger engine braking during deceleration.

Improved Driving Feel
By its nature, a CVT delivers a noticeably different driving feel for the customer, and so a manufacturer must use careful tuning and special control software to ensure a satisfying driving experience. Mitsubishi’s INVECS III software customizes the CVT shift strategy to match the acceleration and braking patterns of each driver, providing better drivability and responsiveness.

With a conventional automatic, when the driver presses on the accelerator, engine and vehicle speeds climb in unison, with perceptible rev drops between gearshifts. The Mitsubishi CVT, on the other hand, allows the engine to rev to its optimal-efficiency speed for a given throttle opening and vehicle load, adjusting the ratio to match the power demands.

The overall affect of the “car catching up with the engine” may seem surprising to a driver at first. Also, since the CVT is designed to keep the engine running at an optimal speed over a wide range of vehicle speeds, pressing on the accelerator pedal will increase vehicle speed but won’t necessarily change the engine sound – another trait that customers may find unusual at first.

After quick acclimation to the CVT, drivers come to appreciate its seamless operation. The Mitsubishi INVECS III software even simulates the slight off-the line lurch that drivers feel and expect in a conventional automatic transmission vehicle. Without this programming, CVT response could be perceived as sluggish.

Source: Mitsubishi

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