2006 Mitsubishi Raider - powertrain

The 2006 Mitsubishi Raider offers truck buyers the choice of two capable drive trains. Both are engineered to provide a smooth, responsive power in everyday driving, and also deliver maximum performance and capability off road, hauling or towing a heavy load. The base 3.7-liter, SOHC 12-valve V6 engine is mated to either a six-speed manual transmission or a four-speed automatic transmission with overdrive. The Raider's V6 produces 210 horsepower at 5200 rpm and 235 lb-ft of torque at 4000 rpm. It is available in the LS and DuroCross trim levels, in both cab styles. The available 4.7-liter, SOHC 16-valve V8 engine delivers 230 hp at 4600 rpm and 290 lb-ft of torque at 3600 rpm. The Raider is the only truck to offer a V8 engine in the mid-size import brand truck class, and is offered as an available option in the DuroCross and standard on the XLS in both cab styles. All trim lines and engines are available in two-wheel drive or four-wheel drive. The XLS adds full-time all-wheel drive as standard.

3.7-Liter SOHC V6 Engine

The Raider's longitudinally-mounted 3.7-liter, 90-degree, SOHC, 12-valve V6 engine combines responsive power, durability and refinement, while being economical to operate. By combining premium materials and modern design, this flexible, V6 engine provides an exceptionally smooth, quiet ride.

Two of the engine's design priorities were to optimize performance while reducing noise, vibration and harshness (NVH). The 90-degree 3.7-liter engine utilizes a cast iron block, with aluminum cylinder heads with single overhead cams on each bank. Splayed valves and generous yet uniform intake ports help promote a consistent and efficient distribution of the air-fuel mixture into the combustion chambers. The engine's proven two-valves-per-cylinder port configuration is designed to help boost low-end torque and make the motor more compact to improve packaging. The compact V6 engine's 3701 cc of displacement are achieved with a 3.57 mm bore and a 3.40 mm stroke.

The V6 engine's lightweight composite intake manifold features individually tuned short runners for improved performance and to help produce torque and power peaks at higher engine speeds. The manifold's smooth polymer construction provides more airflow than a cast aluminum manifold with the same dimensions, and its light weight helps to lower the engine's center of gravity. Use of composite materials also helps to mitigate NVH. The manifold walls are thickened at the rear and bottom of the component, and a sound-absorbing pad located between the intake manifold and block significantly subdues engine noise. High-pressure cast aluminum pistons, robust forged metal connecting rods, and a steel crankshaft are designed to help reduce reciprocating mass, increase strength and allow the engine to rev at high speeds. The V6 engine is also equipped with a balance shaft assembly that helps improve smoothness at idle in particular.

The V6 cylinder heads are designed to breathe freely, rev easily, and meet ever more stringent emissions targets. Spark plugs are located near the center of an efficient combustion chamber designed to promote optimal flame travel, extract the maximum amount of energy from the combustion, and increase efficiency while resisting potentially damaging detonation or knock.

The overhead camshafts are driven using three chains with an intermediate shaft to provide chain speed reduction and to ensure reliability. The alternator, power steering pump and air conditioning compressor are mounted directly on the front cover of the engine to provide more precise alignment of the accessory drive. This arrangement also helps minimize belt wear and noise. An automatic tensioner for the single serpentine poly-vee belt ensures a lifetime of reliability. The design of the composite valve covers with thick molded material in strategic sections as well as internal ribbing helps dampen valvetrain noise better than a steel valve cover.

In the interest of durability and to help protect against oil or fuel leaks, the Raider is equipped with a stainless steel fuel rail finished with premium sealing materials to prevent leaks. An oil filter drip trough is used to prevent oil drained from the filter from running onto chassis parts. The engine uses reduced-tension piston oil control rings and 5W-20 oil instead of 10W-30, which helps reduce friction for better fuel economy.

The Raider's V6 uses a sequential multi-port electronic returnless fuel injection (MPFI) system. Relying on commands from the sophisticated Powertrain Control Module (PCM) computer, fuel is injected directly into each intake port using a fuel map programmed for higher output, along with fast throttle response.

V-6 Fuel Economy

The Raider's V6 with a 9.7:1 static compression ratio requires only regular unleaded fuel. With a manual transmission, EPA fuel economy is estimated at 16 city / 22 highway miles per gallon for 2WD models, and 16 city / 20 highway mpg for 4WD models. With an automatic transmission, fuel economy is estimated at 17 city / 22 highway mpg for 2WD, and 15 city / 19 highway mpg for 4WD models.

4.7-Liter SOHC V8 Engine

Similar in overall design to the 3.7 V6, the Raider's longitudinally-mounted 90-degree 4.7-liter, SOHC, 16-valve V8 engine utilizes a cast iron block and two cast aluminum cylinder heads with a single overhead camshaft per bank and two valves per cylinder. Essentially a 3.7-liter V6 with two more cylinders, the 4.7-liter V8 achieves its 4701 cc displacement with a 93 mm bore and an 86.5 mm stroke. The V8's reciprocating assembly is comprised of the same premium cast and forged metal materials as the smaller V6. The 4.7-liter V8 engine is enhanced using lighter weight hollow camshafts with steel lobes, magnesium valve covers and a molded composite intake manifold. These measures help the engine maintain low mass while providing responsive power across the rev range. A noise-reducing compound molded into the accessory drive belt keeps it operating quietly even after years of use.

Like the V6, the V8 engine uses a tuned-length runner composite intake manifold and free-flowing cold air induction system, and heads that feature fast-burn combustion chambers. The static compression for the 4.7-liter engine is 9.0:1 and is equipped with dual knock sensors that permit more spark advance and help mitigate potential detonation. The engine's additional displacement helps to create the extra torque and horsepower that makes the V8-equipped Raider the ideal vehicle for towing and hauling.

Intake/Exhaust

The Raider V6 and V8 engines' exhaust systems are designed for durability and tuned for performance, while also keeping noise in check and reducing emissions. Tri-layer exhaust system heat shields are formed from two layers of aluminized steel crimped around a layer of pure aluminum, which is lighter and easier to form than a single layer of steel, and has improved insulating and noise control properties. This provides better corrosion protection with reduced noise radiation.

Both Raider engines are equipped with a cold air induction system to help quiet induction noise. The Raider uses an air cleaner housing and an engine-mounted resonator assembly to help reduce radiated induction noise, as well as an additional resonator upstream of the air cleaner. A flexible duct connects the air cleaner housing and the engine-mounted resonator, providing a more effective seal over the life of the system. An engine-mounted air box assembly houses two resonators with unique sound canceling tuning for each engine configuration. The exhaust system includes two close-coupled catalytic converters, one for each bank of the engine. Both are mounted close to the engine, which enables them to reach operating temperature and begin controlling emissions more quickly.

Powertrain Control Module

The Powertrain Control Module is the computer (PCM) that electronically controls all engine and transmission combinations, and is available in manual and automatic transmission versions. With an automatic transmission, the PCM uses two microprocessors. The manual transmission version uses only one microprocessor and less hardware, as well as a simplified harness. The PCM controls fuel delivery and spark events.

The PCM helps improve idle quality, adds transmission functionality, reduces exhaust emissions and provides better diagnostic capabilities. It is programmed with a combination of throttle position points, spark advance curve, and fuel injection rate needed to produce the required engine output and torque based on operator input.

To maintain smooth operation in anticipation of changes in air conditioning compressor operation, alternator loads and power steering loads - which can change operating speeds - the engine controller builds a torque reserve. When these situations are about to occur, the controller adjusts ignition timing and engine airflow before the change takes place, and then again as the change occurs to keep engine speed constant. The controller not only anticipates the timing of the change, but also the amount of change required.

The PCM also provides an alternator charging rate control with a battery temperature sensor input to ensure a charging rate appropriate to the operating conditions. To prevent the driver from re-starting the engine when it is already in operation, a starter override feature automatically disengages the starter to prevent overrun.

Both engines use 136-ampere alternators with a 600 CCA (Cold-Cranking Ampere). An insulating battery wrapper extends battery life by reducing its temperature during heavy-load hot-weather operation.

V-8 Fuel Economy

The 4.7-liter engine produces V8 power and torque (230 hp at 4600 rpm and 290 lbs.-ft of torque at 3600 rpm) while achieving a fuel economy level on par with some competitors' six-cylinder engines. Estimated fuel economy is 15 city / 20 highway mpg for 2WD, 14 city / 19 highway mpg for 4WD. Both the V6 and V8 engines have a 50-state emissions system calibration that meets federal Bin 10A emissions standards and California LEV1 standards.

Powertrain Mounts

The 2006 Raider uses pre-loaded elastomeric bushings for the front powertrain mounts that are tuned through computer-aided analysis and testing to ensure that the natural frequency of the powertrain assembly does not couple with that of the frame. The frequencies of such vibrations tend to be perceived by the driver as frame-borne shakiness. The engine's front mounts are located and angled so that they limit torsional motion of the engine during the application of power. A new two-path mount at the transmission, with paths angled shared with the front mounts, duplicates the benefit of focusing torsional movement to help avoid creating vibration in other directions. The powertrain mounts use a tuned durometer rubber isolation member compressed into its mounting bracket to ensure durability. The Raider's 2WD and 4WD each require different calibrations because the added weight of the 4WD front axle bolted to the engine requires some modification. All of these components help reduce idle vibration transmitted to the frame, and add a sense of refinement to the truck's ride quality.

Transmissions

The Raider offers three transmission options between the four models. The Getrag 238 six-speed overdrive manual transmission is offered on all LS Extended Cab models with the 3.7-liter V6. It uses closely spaced ratios, which improve fuel economy and engine response in everyday driving. A low first gear ratio provides a smoother ride during launching and low-speed acceleration. For easy shifting, the transmission features triple-cone synchros on first and second gears and double-cone synchros on third and fourth gears. Multiple-cone synchros ensure the gears engage smoothly and quickly, during both upshifts and downshifts with nominal effort. An overdrive sixth gear reduces the need for downshifting to maintain cruising speed on rolling or hilly roads. The transmission's gearsets are power honed to help minimize gear noises.

Six-Speed Gear Ratios

Automatic Transmissions

A four-speed overdrive automatic transmission is available on all models with the 3.7-liter V6 engine, and a five-speed overdrive automatic transmission is available on all models with the 4.7-liter V8 engine.

Both transmissions use an Electronically Modulated Converter Clutch (EMCC), which allows the torque converter clutch to engage at steady speed driving in third, fourth or fifth gears. When uncontrolled, converter slippage at cruising speeds is about 250 rpm. During partial engagement, slippage is maintained about 60 rpm by modulating the hydraulic pressure that applies the converter clutch. EMCC disengages immediately when acceleration is needed. It isolates the driveline and passengers from engine power pulses, thus avoiding noise and vibration. EMCC also improves transmission durability by reducing transmission fluid and engine coolant temperatures when climbing grades. Grooved friction material allows ongoing slippage in the torque converter while retaining full durability.

Another feature found in automatic transmission-equipped Raiders is Part-Throttle Torque Management which provides smooth, quick shifts over a wider range of throttle openings. This electronic feature reduces energy dissipation to eliminate harsh quick shifts by reducing spark advance to the engine for approximately 0.25 second. The processor identifies the type of shift (up or down), when to reduce spark advance and when to resume. The adjusted spark advance events are computed in real time for each shift based on the operating speeds of the required mechanical shift elements. The operation is monitored every two milliseconds for correct execution.

The Powertrain Control Module (PCM) also initiates downshifts during deceleration to keep the engine speed higher than the transmission output speed. During deceleration, the PCM regulates idle airflow using the idle air control system to keep the engine speed slightly above the transmission input shaft speed the vehicle decelerates. As the shift occurs, the PCM briefly increases idle airflow to provide an idle speed that matches the higher speed expected in the lower gear. The transaxle downshifts to third and then second gears during deceleration, anticipating the "kick-down" that would otherwise occur after the accelerator is depressed. When the driver reopens the throttle the vehicle will accelerate smoothly. If deceleration continues after the shift is complete, the PCM continues regulation until the normal idle speed is reached or acceleration begins.

The four-speed automatic on the V6 equipped Raider uses Electronically Controlled Hydraulic Pressure to help control the efficiency-sapping parasitic losses using a two-stage transmission fluid pump with electronic output pressure control. During normal driving conditions, the pump pressure control system monitors clutch torque requirements and adjusts the pump pressure accordingly, often using only half the available pressure. The primary stage of the pump works continuously; output from the secondary stage is adjusted by an electronically controlled variable-force solenoid valve. When clutch pressure demand is low, this valve allows flow from the second stage to return directly to the sump, consuming minimal power. As driving conditions change, and when additional pressure is needed, the variable-force solenoid closes the valve, increasing fluid pressure in proportion to demand, for swifter, firmer engagement.

The five-speed automatic transmission provides a second overdrive ratio for increased highway fuel economy and reduced engine noise at highway speeds. The additional overdrive gear reduces engine speed by 12 percent relative to fourth gear.

Transfer Cases

Four-wheel drive Raider models benefit from added traction on snow, ice or other low-traction surfaces. Full-time four-wheel drive, available on the XLS trim level, transmits even more torque to all wheels during dry or slippery conditions. This is due to its center differential that allows the front and rear drive shafts to rotate at different speeds on dry pavement without damaging the drivetrain. Two-speed (high and low range), part-time four-wheel drive provides added traction when necessary by locking the front and rear axles together, but should only be used on low-traction areas to prevent lash-related damage to the drivetrain.

On low-traction, low-speed conditions, such as slow climbing, the all-wheel drive mode multiplies engine torque and locks the front and rear axles together so they rotate at the same speed for optimum performance. Both transfer cases are put through rigorous tests equivalent to 150,000 miles to insure durability.

Front and Rear Axle

On 4WD-equipped Raider models, the front axle uses premium shafts, seals and a new, stronger pinion nut design. The differential vent hose terminates high in the engine compartment to help keep out water when crossing shallow waterbeds or driving in flood conditions.

All Raider rear axles rely on carrier and tube construction with either 8.25- or 9.25-inch ring gears combined with 3.55 and 3.92 axle ratios. Both are available with anti-spin differentials. An available 3.21 axle ratio in both ring gear sizes offers better fuel economy when paired with the Getrag manual transmission.

Mitsubishi Motors North America, Inc., (MMNA) is responsible for all manufacturing, finance, sales, marketing, research and development operations of the Mitsubishi Motors Corporation in the United States. Mitsubishi Motors sells coupes, convertibles, sedans and sport utility vehicles through a network of approximately 570 dealers. 

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