Honda released detailed information on the new 2009 Acura MDX, priced from $40,790 up to $48,690. The 2009 Acura MDX is powered by a 3.7-liter, SOHC, V6 engine that outputs 300 hp at 6,000 rpm and 275 lb-ft of torque at 5,000 rpm. The engine features a VTEC (Variable Valve Timing and Lift Electronic Control) valvetrain and a 2-piece, dual-stage magnesium intake manifold. The engine of the 2009 Acura MDX is coupled with a Sequential SportShift 5-speed automatic transmission and the car comes equipped with the Super Handling All-Wheel Drive (SH-AWD) system.
The 2009 Acura MDX complies with the EPA TIER 2 - BIN 5 and CARB LEV II ULEV emissions standards and has an EPA estimated mileage of 15/20 mpg (city/highway).
2009 Acura MDX in Detail:
2009 Acura MDX – Introduction
OVERVIEW
Benchmarked against some of the best performance SUVs in the world and tuned on the Nürburgring
racetrack in Germany, the MDX clearly establishes itself as a driver's SUV. Outfitted with Acura's Super Handling All-Wheel Drive™ (SH-AWD®) system and an available Sport Package with Active Damper System, the MDX yields a combination of handling and comfort that is truly on the cutting edge.
The 2009 MDX is equally daring in its styling and thorough in its safety and environmental responsibilities. The MDX has an expansive array of safety features included as standard equipment. The MDX's 300-hp VTEC® V-6 makes as much power as some competitive V-8s, yet delivers ultra-low emissions and excellent fuel economy.
Inside the 7-passenger interior, the MDX offers thoughtful luxury and an unmatched range of advanced technologies, including the Acura Navigation System with Voice Recognition™ and AcuraLink® Satellite Communication System with real-time traffic and a spectacular 10-speaker Acura/ELS Surround® Premium Sound System.
Altogether, the 2009 MDX embodies Acura's commitment to performance, luxury, quality and style, along with an emphasis on safety and environmental care. The 2009 MDX is the seventh Acura project
to be designed and engineered in the United States (including the 1997 CL, 1999 TL, 2001 CL, 2001 MDX, 2004 TL and 2009 TL) along with several award-winning Honda products.
POWERTRAIN FEATURES
3.7-liter, SOHC, V-6 engine
300 horsepower @ 6,000 rpm
275 lb-ft of torque @ 5,000 rpm
VTEC® (Variable Valve Timing and Lift Electronic Control) valvetrain
2-piece, dual-stage magnesium intake manifold
Sequential SportShift 5-speed automatic transmission
Super Handling All-Wheel Drive™ (SH-AWD®)
EPA estimated mileage of 15/20 mpg* (city/highway)
EPA TIER 2 - BIN 5 and CARB LEV II ULEV emissions standards
*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.
BODY & CHASSIS FEATURES
Unit body structure with extensive use of high-strength steel
Xenon High-Intensity Discharge (HID) low-beam front headlights
MacPherson strut fully independent front suspension
Multi-link independent rear suspension
Torque-sensing, variable power-assist rack-and-pinion steering
18x8-inch aluminum wheels
P255/55R18 104H M+S all-season tires
4-wheel anti-lock braking system (ABS) with Electronic Brake Distribution (EBD) and Brake Assist
Vehicle Stability Assist™(VSA®) with traction control and Trailer Stability Assist
Tire Pressure Monitoring System (TPMS)
5,000-pound tow rating
LED tail lamps and Center High Mounted Stop Light (CHMSL)
Heated outside mirrors with Reverse gear tilt-down and integrated LED directional turn signals
INTERIOR FEATURES
7 passenger seating
Driver-oriented cockpit
Driver's 10-way power seat (8-way power seat with 2-way power lumbar support)
Electronic tilt and telescoping steering column
Two-driver custom memory system
Front passenger 8-way power seat
Heated front seats
Tri-Zone automatic climate control system with air filtration and humidity control
253-watt Acura Premium Sound System with AM/FM tuner, in-dash 6-disc CD/MP3/WMA changer, XM® satellite radio, AUX jack connectivity along with 8 speakers, including 8-inch subwoofer
HomeLink® remote control
Multi-Information Display (MID) allows access to multiple electronic functions
Maintenance Minder™
Adaptive and flexible cargo space with multiple configurations
Bluetooth® HandsFreeLink® wireless telephone interface
Auto dimming rearview mirror
SAFETY FEATURES
Advanced Compatibility Engineering™ (ACE™) body structure
Side impact door beams
Impact-absorbing crumple zones (front/rear)
Driver and front passenger dual-stage, dual-threshold airbag Supplemental Restraint System (SRS)
Driver and front passenger knee bolsters
Driver and front passenger side airbags with front passenger Occupant Position Detection System (OPDS)
Side curtain airbags for all three rows with rollover sensor
Active front head restraints
3-point adjustable-height front seat belts with automatic tensioning system and load limiters
3-point seat belts at all seating positions
Automatic Locking Retractor/Emergency Locking Retractors (driver has ELR only)
LATCH (Lower Anchors and Tethers for CHildren) child-seat mounting system for the second-row seats
Technology Package
Acura Navigation System with Voice Recognition™ and rearview camera
AcuraLink® satellite communication system with real-time traffic
410-watt, 10-speaker Acura/ELS Surround® Premium Sound System with 6-disc CD/DVD-Audio and DTS® changer, AM/FM tuner, XM® Satellite Radio and AUX jack connectivity
GPS-linked, solar-sensing, tri-zone, automatic climate control system with air filtration and humidity control
Power operated rear tailgate
Sport Package (in addition to the Technology Package features)
Active Damper System
Perforated, premium full-grain leather seating surfaces with high-damping front-seat cushion foam
Exclusive alloy wheel design
Auto-leveling headlights
Textured metallic accents on radio, cupholder and shifter bezel
Entertainment Package (available with Technology or Sport Package)
DVD Rear Entertainment System with wireless headphones and remote control
115-volt power outlet in center console
Heated second-row outboard seats
MARKET SUMMARY
MDX has been very important to Acura, accounting for about 30-percent of the division's sales since the vehicle's introduction as a 2001 model. Equally important, the original MDX attracted buyers from competitive luxury makes including BMW, Mercedes-Benz and Lexus, starting new relationships for Acura. The 2009 MDX competes in the Mid Premium CUV (Crossover Utility Vehicle) segment.
TARGET CUSTOMER
Focus groups with luxury customers were conducted in Seattle, Detroit, Chicago and Los Angeles. These cities were carefully chosen to explore how customers use their SUVs in cold climates, in areas that are traditional domestic-vehicle strongholds and in areas known for their trend-setting character.
Early in the study process Acura also benchmarked performance SUVs such as the BMW X5 - and polled their owners - to ensure that the second generation MDX would exceed its performance. Satisfying these highly discriminating customers means that the MDX would be well positioned to attract a wider group of potential buyers.
With the MDX, added performance and handling capabilities boost its appeal for performance enthusiasts, while the luxurious and functional interior continues to satisfy the needs of traditional luxury customers.
ENGINE & POWERTRAIN
Developing 300 horsepower and 275 lb-ft of torque, the MDX's 3.7-liter V-6 output is competitive with many V-8 engines - without the fuel-economy penalty most V-8's suffer. To widen the powerband and improve fuel economy, the 3.7-liter engine has VTEC® (Variable Valve Timing and Lift Electronic Control) valvetrain, a dual-stage intake manifold and an electronic Drive-by-Wire™ throttle system. EPA estimated mileage of 15/20 mpg* (city/highway) and a large 21-gallon fuel capacity mean the MDX has a long cruising range. The MDX is designed to meet the latest emissions requirements including strict EPA TIER 2 - BIN 5 and CARB LEV II ULEV standards.
A 5-speed automatic transmission with Sequential SportShift is designed to satisfy the most performance-oriented drivers. Tuned on the famed Nürburgring circuit in Germany, the Super Handling All-Wheel Drive™ (SH-AWD®) system provides handling precision that sets a new benchmark for SUVs.
SH-AWD® actively varies the torque distribution between front and rear axles - then between the left and right rear wheels - to provide maximum grip under all driving circumstances. Such torque vectoring operates seamlessly and allows the SH-AWD® to overdrive the outside rear wheel up to 1.7-percent faster than the front wheels to create a "yaw moment" allowing the MDX to better rotate around a corner while minimizing understeer.
*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.
BODY & CHASSIS
The 2009 MDX sets new standards for SUV styling, engineering, handling and safety standpoints. Its dramatic styling utilizes large surface areas, sweeping curves and decisive angles. Longer, wider and lower (and with a longer wheelbase) than the original MDX, the dimensions create a more athletic appearance.
In an effort to keep mass out of the vehicle, the MDX features widespread use of light weight materials such as high-strength steel, aluminum and magnesium. In addition, the Advanced Compatibility Engineering™ (ACE™) body structure is intended to bring new levels of front crash safety to the MDX.
Befitting its position as Acura's flagship SUV, the MDX is equipped with Xenon High-Intensity Discharge (HID) low-beam front headlights, a dramatic array of Light Emitting Diodes (LEDs) in the rear tail lamps and center high-mounted stop light (CHMSL), and exterior mirror-mounted turn signals. The Acura signature front grille reflects a fresh look for the MDX. Careful aerodynamic tailoring reduces drag noise and high speed dynamic stability.
The 2009 MDX features a track-tuned chassis to complement its 300-horsepower VTEC® V-6 engine and Super Handling All-Wheel Drive™ (SH-AWD®). Engineers targeted the BMW X5 and Porsche Cayenne when developing the MDX chassis, and then tested and refined it at Germany's famed Nürburgring circuit. The Active Damper System, available in the Sport Package, has proprietary fully active dampers that adjust (in less than five milliseconds) to road conditions on a real-time basis. The MDX is also at home off-road where its excellent engine torque, responsive suspension, and generous ground clearance enable it to cross-step through rough terrain.
For family recreation, the MDX tows as well as it goes. With a 5,000-pound tow rating, standard trailer pre-wiring, high-capacity radiator with twin cooling fans, transmission fluid cooler and Trailer Stability Assist, the MDX needs only a dealer-installed hitch and wiring to tow a substantial trailer.
INTERIOR
The MDX features a luxurious yet functional interior. The cockpit environment is focused on the driver, and features a host of technologies to make driving simultaneously rewarding and relaxing. The interior styling and functionality perfectly coexist with a driver's cockpit that features a 10-way power seat including power-adjustable lumbar support for the driver, electronic tilt and telescoping steering column, a 2-position custom memory system, and a Multi-Information Display (MID) that allows access to multiple electronic functions.
The interior design is as dynamic and contemporary as the exterior, with a "4+3 seating" concept that luxuriously hosts four passengers in the first and second row seats, while also offering comfortable accommodations for three additional passengers (one in the second row and two in the third row). The front passenger enjoys an 8-way power seat, while everyone on board will appreciate the MDX's Tri-Zone automatic climate control system. All occupants will enjoy the 253-watt, 8-speaker Acura Premium Sound System with in-dash 6-disc CD/MP3/WMA changer, AM/FM tuner, and XM® Satellite Radio. An auxiliary jack for personal audio devices is also included. Standard convenience features include HomeLink®, Maintenance Minder™ and adaptive and flexible cargo space with six configurations.
SAFETY
The Advanced Compatibility Engineering™ (ACE™) body structure along with several passive-safety technologies help bring the 2009 MDX to the next level of safety. ACE™ more evenly distributes collision forces and helps maintain the integrity of the passenger cabin in the event of a severe frontal collision. The MDX is also less intrusive to smaller vehicles in a head-on collision thanks to a special frame member located below the front bumper that is designed to engage the front bumper of smaller vehicles.
The MDX is equipped with an active front head restraint system for front seat head restraints along with knee bolsters for the driver and front passenger. The driver and front passenger are also protected by dual-stage, dual-threshold airbag Supplemental Restraint System (SRS) and side airbags with front passenger Occupant Position Detection System (OPDS). Side curtain airbags help reduce the likelihood of injury to the occupants in all three rows of outboard seats A rollover sensor adds a further level of protection.
The 2009 Acura MDX furthers Acura's commitment to "Safety Through Innovation" with pedestrian injury mitigation features such as a deformable aluminum hood and hood hinges along with breakaway windshield-wiper pivots.
MANUFACTURING QUALITY
Honda of Canada Manufacturing in Alliston, Ontario, is the assembly plant for the MDX. A special dynamic quality-control process is employed to ensure the highest possible level of attention to detail for every MDX produced. After assembly is completed, each MDX enters a special Acura Quality line. The ability to immediately respond to the smallest quality issue allows the MDX to excel in quality - and in customer satisfaction.
2009 Acura MDX – Powertrain
OVERVIEW
Given the MDX's performance goals, its powertrain and driveline were required to advance on multiple fronts. The result is one of the most powerful normally aspirated 6-cylinder SUV powerplants currently available in America. In addition, the MDX returns competitive fuel economy and meets tough EPA TIER 2 - BIN 5 and CARB LEV II ULEV emissions standards. To put the power to the ground and provide agile, responsive handling, the MDX has standard Super Handling All-Wheel Drive™ (SH-AWD®).
The MDX's sophisticated 3.7-liter VTEC® V-6 powerplant develops 300 horsepower at 6,000 rpm and 275 lb-ft of torque at 5,000 rpm. The MDX returns an EPA fuel economy rating of 15/20 (city/highway) mpg*.
Compared to the previous generation MDX, the 3.7L engine gains 47 horsepower and 25 lb-ft of torque. Of that gain, 20 horsepower came from an increase in displacement and a new 11.0:1 compression ratio and 15 more horsepower are due to new intake port shapes, valve design and VTEC® tuning. The final 12 horsepower is credited to the 3.7L MDX's high-flow induction and exhaust systems. Although more powerful, the engine is actually 17.2 pounds (3.7-percent) lighter than the 3.5L engine it replaced. Durability upgrades throughout the powertrain, including a high capacity radiator with twin cooling fans and a standard transmission fluid cooler accommodate the MDX's 5,000-pound tow rating.
A 5-speed automatic transmission with Sequential SportShift is standard, giving the driver the choice of fully automatic operation or manual shifting via a special shift gate. With the electronically controlled Drive-by-Wire™ throttle system and transmission working together to execute shifts, the MDX delivers smoothly responsive acceleration.
The MDX has standard SH-AWD®, an exclusive all-wheel-drive system that actively distributes the optimum amount of torque not only between the front and rear axles but also between the left and right rear wheels. The effect of such "torque vectoring" is reduced understeer, superior cornering accuracy and more total cornering performance. For the MDX, SH-AWD® is enhanced with hill logic which automatically adjusts the front/rear torque split based on hill grade.
2009 Acura MDX
Engine SOHC VTECÆ V-6
Displacement 3664cc
Compression ratio 11.0:1
Horsepower @ rpm 300 @ 6,000
Torque @ rpm (lb-ft) 275 @ 5,000
Transmission 5-speed automatic
EPA estimated mileage City/Highway 15/20
Emissions certification (CARB/EPA) TIER 2 - BIN 5 / CARB LEV II ULEV
Fuel type Premium unleaded
POWERTRAIN AT A GLANCE
Engine
3.7-liter, SOHC, V-6 engine produces 300 horsepower at 6,000 rpm and 275 lb-ft of torque at 5,000 rpm
VTEC® (Variable Valve Timing and Lift Electronic Control)
11.0:1 compression ratio
2-piece, dual-stage magnesium intake manifold
Direct ignition system with knock control
Variable flow exhaust system
Drive-by-Wire™ throttle system
Maintenance Minder™ system optimizes service intervals
Transmission and Drive System
Sequential SportShift 5-speed automatic transmission
5-position transmission shifter
Advanced shift-hold control limits upshifts during spirited driving
Advanced Grade Logic Control System reduces gear "hunting" when driving on steep hills
External transmission fluid cooler
Super Handling All-Wheel Drive™ (SH-AWD®)
Noise, Vibration, and Harshness (NVH)
60-degree engine cylinder V-angle for inherently smooth operation
Maintenance-free serpentine accessory drive belt system with auto tensioner
Emissions/Fuel Economy
Dual high-flow, close-coupled catalytic converters plus under floor catalytic converter
High capacity 32-bit RISC processor engine control unit (ECU)
Meets strict EPA TIER 2 - BIN 5 and CARB LEV II ULEV emission standards
15/20 mpg* (city/highway)
*Based on 2009 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.
ENGINE ARCHITECTURE
The 3.7-liter VTEC® V-6 in the MDX is the largest production engine in Acura's history and it incorporates many of the refinements and improvements that have been developed in other Acura powerplants. The MDX engine has a smooth-firing 60-degree V-angle, compact overall dimensions, and it sheds 17.2 pounds from previous generation 3.5L engine. Aluminum alloy block construction including special aluminum cylinder sleeves saves weight and improves cooling, while VTEC® compatible cylinder heads operate four valves per cylinder for maximum power output.
A high-flow intake system, high compression ratio, close-coupled catalytic converters and high flow exhaust team to help the MDX engine produce strong torque.
ENGINE BLOCK
The MDX's lightweight, heat-treated die-cast aluminum-alloy block has unique cast-in-place aluminum cylinder liners. These high-silicon sleeves dissipate heat better than traditional iron liners. The aluminum sleeves also allow a closer piston-to-cylinder clearance for lower operating noise. A mechanical etching process during manufacturing exposes silicone particles embedded in the aluminum sleeves, which provide a hard piston ring sealing surface. The block also incorporates a deep-skirt design for rigid crankshaft support and reduced noise and vibration.
CRANKSHAFT/PISTONS/CONNECTING RODS
The MDX uses a forged-steel crankshaft for high strength with minimum weight. With their raised crowns, the MDX pistons raise the compression ratio (relative to the previous MDX) from 10.0:1 to 11.0:1. This elevated compression ratio is possible due to an oil jet system that sprays cooling oil on the underside of the piston crowns to keep temperatures in check. Steel connecting rods are forged in one piece and then the crankshaft ends are "crack separated," creating a lighter and stronger rod with a perfectly fitted bearing cap.
CYLINDER HEADS / VALVETRAIN
Like other Acura V-6 engines, the MDX powerplant uses single overhead camshaft (SOHC) cylinder heads. These lightweight components are made of pressure-cast, low-porosity aluminum, and improve overall packaging, enhance exhaust flow and allow the optimal positioning of a primary close-coupled catalytic converter on each cylinder bank. To save weight and reduce parts count, an exhaust manifold is an integral part of each cylinder head casting. Magnesium cylinder head covers save a total of 2.6 pounds.
The MDX features lightweight camshafts. Assembled from tubular steel shafts with splined steel lobes and journals that are pressed in place, this unique style of camshaft design is a first for Acura.
The MDX's intake port design has an optimized shape that contributes to the MDX's 300 horsepower output. Intake valves are 36mm in diameter (an increase of 1mm over the previous engine design), yet weigh 13-percent less due to a reduction in material in the valve head. The exhaust valves measure 30mm in diameter.
To ensure positive sealing, a 3-layer shim-type head gasket is used. A single Aramid-fiber reinforced belt drives the overhead camshafts.
VTEC® (VARIABLE VALVE TIMING AND LIFT ELECTRONIC CONTROL)
The MDX's VTEC® (Variable Valve Timing and Lift Electronic Control) operates the 12 intake valves in two distinct modes. Operation of the intake valves changes to optimize both volumetric efficiency and combustion of the air/fuel mixture. At low engine speeds, the intake valves have low lift and are open a comparatively short period of time during cylinder filling. At high engine speeds where breathing is critical, the valves switch to a high-lift, long duration mode to deliver improved volumetric efficiency. The VTEC® changeover point occurs at approximately 4,500 rpm and is virtually undetectable to the driver.
When the engine reaches the VTEC® changeover point, the powertrain control module (PCM) triggers the opening of an electric spool valve that routes pressurized oil to small pistons located in the intake valve rocker arms. The pistons slide into position to lock together the three intake rockers for a given cylinder, which then follow a single high-lift, long-duration camshaft lobe.
HIGH FLOW INDUCTION SYSTEM
To improve engine breathing and engine sound, particularly at high rpm and large throttle openings, the MDX has a low-restriction intake manifold system. With a large diameter inlet, a pair of resonators and a low-restriction air filter element, the 3.7L MDX induction system flows an additional 14-percent more than the previous 3.5L system.
DRIVE-BY-WIRE™ THROTTLE SYSTEM
The MDX doesn't use a conventional throttle cable, but instead has smart electronics that connect the throttle pedal to the electronic throttle-body. A programmed "gain" between throttle pedal and engine offers better drivability and optimizes engine response to suit driving conditions. The throttle profile of the new MDX provides low speed control, followed by progressively building response at higher speed for improved linearity.
The Drive-by-Wire™ throttle system evaluates the driving conditions by monitoring throttle pedal position, throttle-body opening position, road speed, and engine speed. This information is used to define the throttle control sensitivity. This gives the MDX throttle pedal a predictable and responsive feel that better meets driver expectations.
PROGRAMMED FUEL INJECTION (PGM-FI)
The MDX features a Multi-Point Programmed Fuel Injection (PGM-FI) system that continually adjusts the fuel delivery to yield the best combination of power, low fuel consumption and low emissions. Multiple sensors constantly monitor critical operating parameters such as throttle position, intake air temperature, coolant temperature, ambient air pressure, intake airflow volume, intake manifold pressure, exhaust-air ratios and the position of the crankshaft and cams.
2-PIECE DUAL-STAGE INTAKE MANIFOLD
The MDX uses a dual-stage intake manifold that is designed to deliver excellent airflow to the cylinders across the full range of engine operating speeds. The 2-piece manifold is also very light due to its cast magnesium design. The light-weight manifold combines with the new exhaust system to contribute 12 horsepower to the MDX's 300 horsepower total.
The induction system significantly boosts torque across the engine's full operating range by working in concert with the VTEC® valvetrain. Internal passages and two butterfly valves within the intake manifold are operated by the powertrain control module (PCM) to provide two distinct modes of operation by changing plenum volume and intake airflow routing.
At lower rpm these valves are closed to reduce the volume of the plenum and effectively increase the length of inlet passages for maximum resonance effect and to amplify pressure waves within each half of the intake manifold at lower rpm ranges. The amplified pressure waves significantly increase cylinder filling and torque production throughout the lower part of the engine's rpm band.
As the benefits of the resonance effect lessen with rising engine speed, the butterfly valves open at 3,800 rpm to interconnect the two halves of the plenum, increasing its overall volume. An electric motor, commanded by the PCM, controls the butterfly valves. The inertia of the mass of air rushing down each intake passage helps draw in more charge than each cylinder would normally ingest. The inertia effect greatly enhances cylinder filling and the torque produced by the engine at higher rpm.
DIRECT IGNITION AND DETONATION/KNOCK CONTROL
The MDX's powertrain control module (PCM) monitors engine functions to determine the best spark timing. An engine-block-mounted acoustic detonation/knock sensor "listens" to the engine, and based on this input, the PCM retards the ignition timing to prevent potentially damaging detonation. The MDX has a coil unit for each cylinder that is positioned above each spark plug's access bore.
CLOSE-COUPLED CATALYSTS AND VARIABLE FLOW EXHAUST SYSTEM
The exhaust manifolds of the 3.7L V-6 are cast directly into the aluminum cylinder heads to reduce weight and to put the engine's two primary catalytic converters as close as possible to the combustion chambers. The 600-cell per-square-inch, high-efficiency catalytic converters mount directly to the exhaust port of each cylinder head for extremely rapid converter light-off after the engine starts -- thus lowering emissions output. A significant weight savings and reduction in parts count is realized by eliminating a traditional exhaust manifold and converter design.
Downstream of the close-coupled catalysts, a hydroformed 2-into-1 collector pipe carries exhaust gases to a single secondary catalytic converter located under the passenger cabin. This high-flow unit has a revised shape and a large 62mm outlet. Downstream of the underfloor catalyst, the system splits flow into a pair of underfloor chambers (the previous MDX used a single chamber) to give the exhaust note a more refined sound. Dual silencers near the rear fascia incorporate an exhaust pressure-activated valve to balance the engine's need for proper exhaust backpressure at low rpm and free flow at high rpm. With the valve in each silencer closed, the exhaust sound level is muted for quiet cruising. When exhaust flow increases sufficiently due to high rpm and a large throttle opening, the silencer valves open and provide a secondary exit path inside the silencer chamber. In total, the MDX's exhaust system refinements substantially improve flow potential.
EMISSIONS CONTROL
The 2009 MDX meets tough EPA TIER 2 - BIN 5 and CARB LEV II ULEV emissions standards, and per regulations, is certified to this level of emissions performance for 120,000 miles.
A number of advanced technologies are factors in this excellent emissions performance. The cylinder-head-mounted close-coupled catalysts light off quickly after engine start up, and a 32-bit RISC microprocessor in the powertrain control module (PCM) boosts computing power to improve the precision of spark and fuel delivery. In particular, right after startup, better fuel atomization is provided by the high-efficiency multi-hole fuel injectors that more accurately deliver fuel to each cylinder.
The MDX's Multi-Point Programmed Fuel Injection (PGM-FI) system monitors the state of the exhaust gas and tracks multiple engine inputs including intake manifold pressure, throttle position, intake air temperature, coolant temperature, and such. Based on these inputs PGM-FI continuously adjusts and optimizes the amount of fuel delivered to each cylinder.
ONE-TOUCH STARTER SYSTEM WITH HIGH-POWERED STARTER
To ensure consistent starting, the MDX has a one-touch starter system that maintains starter engagement until the engine starts, even if the driver releases the ignition switch.
AIR CONDITIONER SYSTEM EFFICIENCY
To provide greater driving range while maintaining a comfortable interior climate, the MDX has excellent air conditioner efficiency. By partially mixing cool cabin air with fresh air in the blower, the amount of compressor operation can be reduced by up to 40-percent compared to operating exclusively on exterior air. Over the course of a tank of fuel, this partial recirculation mode can extend fuel economy by as much as 4-percent. This function operates automatically when the HVAC system is in Auto mode.
NOISE, VIBRATION AND HARSHNESS CONTROL
The MDX powerplant is exceptionally smooth thanks to its 60-degree cylinder V-angle and compact, rigid and lightweight die-cast aluminum cylinder block. A forged crankshaft, die-cast accessory mounts and a stiff cast-aluminum oil pan also help reduce noise and vibration.
5-SPEED AUTOMATIC WITH SEQUENTIAL SPORTSHIFT AND GRADE LOGIC CONTROL
The MDX has a standard 5-speed automatic with Sequential SportShift and Grade Logic Control to maximize acceleration performance, fuel economy and driver control. Compared to the previous generation MDX, this sophisticated transmission features lower gear ratios for improved acceleration and towing power, upgraded shafts, gears, bearings and clutches to match the engine's greater power output and increased cooling capacity to accommodate the MDX's 5000-pound towing capacity.
Designed for a high level of durability and low maintenance, the MDX transmission has a strengthened aluminum case that carries both high-torque clutches and high-strength gears. A transmission cooler is positioned in the front of the MDX to help keep the transmission fluid temperature within tolerance, particularly when towing.
Automatic Mode
The Sequential SportShift 5-speed transmission can be operated in conventional fully automatic mode via a console-mounted shifter. The Grade Logic Control System and Shift Hold Control are integrated into the shift programming to reduce gear "hunting" and unnecessary shifting.
While traveling uphill or downhill, Grade Logic Control alters the transmission's shift schedule, reducing shift frequency and improving speed control. Throttle position, vehicle speed and acceleration/deceleration rate are continuously measured, then compared with a map stored in the transmission computer. When the system determines the MDX is on a hill, the shift schedule is adjusted to automatically hold the transmission in a lower gear for better climbing power or increased downhill engine braking.In spirited windy road driving, where the throttle is quickly released and the brakes are applied (as might be the case when decelerating to enter a corner), Shift Hold Control prevents upshifts to higher gears (4th and 5th). This reduces disturbance to the chassis and ensures abundant power is immediately available without a downshift. On curving roads, Shift Hold Control significantly improves throttle responsiveness and reduces unnecessary shifting.
Manual Mode
The Sequential SportShift transmission can be shifted into manual mode by moving the console-mounted gear selector lever laterally to a special gate to the left of the "Drive" position. When in manual mode, a forward push of the selector lever commands an upshift, while a rearward pull commands a downshift. The current transmission gear is shown in a digital display within the tachometer face. To heighten control and driver involvement, special shift logic in manual mode delivers quicker, firmer shifts than in fully automatic mode.
An array of features are active when the transmission is in manual mode to help protect the engine and drivetrain from inadvertent damage. The ECU cuts off fuel flow to the engine if there is a possibility of over revving. In the rare situation where the fuel cutoff alone is unable to prevent engine over revving (as could happen on a steep downhill) the transmission will upshift itself to prevent engine damage. Also, when downshifting, the transmission won't execute a driver-commanded downshift that would send the engine beyond redline in the lower gear. Regardless of the selected ratio, the Sequential SportShift transmission will automatically downshift to first gear as the vehicle comes to a stop thus preventing pulling away from a stop in a higher gear.
5-POSITION SHIFT GATE
The MDX has an intuitive 5-position shift gate that simplifies the operation of the transmission. When operated in automatic mode, the transmission allows the driver to choose D (1st through 5th gear) or D3 (1st through 3rd gear). The D3 position selects only the first three gears for increased engine braking or reduced shifting during city driving.
COOPERATION BETWEEN 5AT AND DRIVE-BY-WIRE
Both shift speed and smoothness are improved by cooperation between the Drive-by-Wire™ throttle system and the electronically controlled automatic transmission. Since the engine can be throttled by the engine management system during upshifts and downshifts, the function of the engine and transmission can be closely choreographed for faster, smoother shifting. As a result, the peak g-forces (or "shift shock") are reduced significantly during upshifts and downshifts.
SUPER HANDLING ALL-WHEEL DRIVE™
The MDX has Super Handling All-Wheel Drive™ (SH-AWD®) as standard equipment. This innovative full-time all-wheel-drive system actively distributes the optimum amount of torque not only between the front and rear axles but also between the left and right rear wheels. This "torque vectoring" improves cornering traction and steering precision by creating a yaw moment that helps the MDX turn. In addition to providing exceptional performance on dry pavement, the MDX's SH-AWD® system provides significant performance gains in snow and ice, as well as similar gains in off road performance. In fact, the SH-AWD® system knows when it is going up a hill and automatically shifts torque to the rear to improve launch traction - done before the vehicle starts to move.
SH-AWD® enhances stability on snow and ice in cooperation with the MDX's VSA® system. During acceleration and cornering, SH-AWD® first maximizes available traction by "preemptively" moving torque to the wheels with the maximum load. However, if the available traction limits are exceeded, the SH-AWD® system can directly modify the drive torque distribution to stabilize acceleration and reduce the potential for oversteer.
Direct Yaw Control promotes precise line trace in all conditions
Full-time "active and intelligent" all-wheel drive requires no driver interaction
SH-AWD® direct control electromagnetic clutches provide ultra-quick response
Grade logic control allows worry-free starting on steep grades with up to 70-percent of available torque being sent to the rear wheels
Up to 70-percent of available torque can be directed to the rear wheels during hill climb acceleration for maximum traction
Up to 90-percent of available torque can be transferred to the front wheels during cruising to help maximize fuel efficiency
In hard cornering, up to 50-percent of available torque can be directed to the rear axle for enhanced chassis balance and increased cornering capability
Up to 100-percent of the torque sent to the rear axle can be applied to either rear wheel as the traction conditions dictate
37-percent increase in rear torque capacity as compared to the previous MDX VTM-4® system
7-percent reduction in weight compared to the previous VTM-4® system
When accelerating on slippery surfaces, cooperation between SH-AWD® and VSA® greatly enhances stability and control
Effect of SH-AWD®
By overdriving the MDX's rear wheels up to 1.7-percent faster than the speed of the front axle, SH-AWD® can provide a "yaw moment" while accelerating into and through tight corners. The torque vectoring ability of SH-AWD® to directly create a yaw moment to allow the vehicle to track exactly as the driver intended is called Direct Yaw Control. This reduces unwanted understeer (or vehicle "push") during everyday driving and when the driver chooses to go for a spirited drive on a favorite stretch of mountain road.
Up to the available traction limits, direct yaw control delivers an uncanny level of precision and driver confidence. Since direct yaw control acts preemptively, VSA® brake and throttle interventions are less intrusive. In changing and challenging road conditions, SH-AWD® reacts to adjust drive torque more quickly than the VSA® can apply stabilizing brake torque.
During acceleration and cornering on slippery surfaces, a conventional 4WD vehicle distributes torque evenly between the two rear wheels. This may lead to loss of traction of the inside rear wheel as load is transferred to the outside wheel due to load transfer during cornering. However with SH-AWD® the side-to-side rear torque distribution varies according to the lateral g (and associated load transfer of the rear tires). For all situations including low-traction roads, the side-to-side torque distribution is naturally aligned with the tire vertical loads. This enhances traction and allows maximum utilization of the available road surface grip during acceleration and cornering.
Electronic Controls and Parameters - VSA®
Vehicle Stability Assist™ (VSA®) is included as standard equipment on the MDX. By continually monitoring the vehicle's operating parameters (such as road speed, throttle position, steering wheel position, accelerating, braking and cornering loads), VSA® anticipates if the vehicle is approaching oversteer or understeer. To help correct either of these situations, VSA® first acts to transfer torque bias to the axle with the most traction. This preventative measure significantly reduces the number of brake and throttle interventions. The response is so quick that the instability may be corrected even before the driver knows it is occurring. Traction Control is integrated into the VSA® which helps the MDX accelerate smoothly on slippery surfaces. The VSA® can request the SH-AWD® to adjust its torque level, thus allowing direct yaw control of the MDX to maximize stability under all driving conditions.
SH-AWD® System Layout
The MDX's SH-AWD® system is closely related to the system in the 2009 RDX. (The system in the RL sedan differs mechanically between the RDX and MDX systems, but is similar in principle.) A torque transfer unit is bolted directly to the front-mounted transaxle. Attached to the front differential's ring gear is a helical gear that provides input torque to the transfer unit. A short horizontal shaft and a hypoid gear set within the case send power to the propeller shaft, which in turn carries it to the rear drive unit. The MDX rear axle is designed to turn up to 1.7-percent faster than the front axle.
Direct Electromagnetic Clutch Systems
Located on either side of the hypoid gear that drives the rear axle, two identical direct electromagnetic clutch systems control the amount of drive torque that reaches each rear wheel. These clutch systems can be controlled as a pair to alter the front/rear torque split or can be controlled independently to allow up to 100-percent of the total rear axle torque to go to one side of the vehicle. The fast acting clutches coupled with smart control logic means traction is maximized in most conditions, without the need for driver intervention.
An electric coil controls the pressure in each clutch device. The amount of available rear axle torque transmitted to each rear wheel can vary continuously, ranging between zero and 100-percent, depending on the conditions. Since the clutches are electromagnetically operated, the amount of drive torque delivered to each rear wheel can be controlled quickly and precisely, reducing wheel slip in low traction conditions.
The clutch packs and friction material are specially designed for the small amount of continuous slip between front and rear axles (created by the 1.7-percent speed differential), while ensuring the expected level of Acura durability. An oil-temperature sensor allows the ECU to estimate the clutch plate coefficient of friction (which changes with heat) in each clutch pack and then adjusts the current sent to the electromagnetic coil that controls the compensation of each clutch. To ensure that the amount of torque transmitted remains optimized as miles accumulate a coil provides a feedback loop that the ECU uses to adjust current to the electromagnetic clutches to compensate for clutch wear.
MAINTENANCE MINDER™ SYSTEM
An Maintenance Minder™ system monitors the vehicle's operating conditions to eliminate unnecessary service visits while ensuring that the vehicle is properly maintained. When the Maintenance Minder™ system determines that maintenance is required, the driver is alerted via a series of messages on the Multi-Information Display (MID). The alerts occur well in advance of required maintenance for scheduling convenience.
This resettable system indicates when maintenance is due on many normal service parts and systems, including oil and filter change, tire rotation, air cleaner, automatic transmission fluid, parts replacement and more. The MID monitors operating conditions such as oil and coolant temperature along with total engine rotations to determine the proper service intervals. Maintenance alerts are presented when the ignition is first turned on, not while driving, unless an urgent need arises. The driver can also check the remaining oil life at any time through the MID.
2009 Acura MDX - Body
OVERVIEW
The 2009 MDX fuses the model's traditional virtues of adaptable space, functionality, safety and environmental responsibility with a more exciting visual presence along with more accomplished handling and ride comfort.
Customers in the luxury SUV arena demand distinctive style. The 2009 MDX ups the game with standard 18-inch wheels and tires, standard Xenon High Intensity Discharge (HID) headlights and a distinctive front grille. Driving excitement is equally embraced with a chassis tuned at the Nürburgring circuit and on autobahns in Germany.
The exterior has bold, clean and advanced styling details with European cache, and it was styled to connect with enthusiast drivers from the moment they first see it. Sitting in the vehicle - and then experiencing it - makes the desire even more intense. Besides featuring a 300 horsepower V-6, the MDX includes Super Handling All-Wheel Drive™ (SH-AWD®), an available Active Damper System along with lightweight aluminum components used in the suspension and body. Convenience features such as an available power rear tailgate further improve functionality and luxury.
EXTERIOR DESIGN GOALS
One of the primary goals in designing the second generation MDX was to keep its traditional strengths but advance its performance and image. The clear direction for the MDX was to create a bold and innovative look that clearly conveyed the "Driver's SUV" nature of the vehicle. The grille is free of molding breaks for a cleaner look and features dark silver satin plating.
STYLING DEVELOPMENT
The original MDX provided a fine blend of utility, luxury and style. The 2009 Acura MDX has powerful, dynamic styling that is a continuation of the themes that have been embodied in recent Acura products. Designers found inspiration in a high-powered mega yacht, which features an exceptionally bold, lean and contemporary design. The challenge was to apply the useful elements of the yacht design to an SUV, and designers found their answer in the adoption of large areas of clean surfaces and the addition of decisive line breaks and dynamic surface curvature. Large 18-inch wheels and tires not only benefit handling, but also create a muscular look. In front, the 2009 MDX has a distinctive, advanced Acura look. The platform is long, low and wide to enhance cornering and high-speed stability.
COMPETITIVE COMPARISON
The MDX has a significantly wider track than its primary market competitors. As a result it offers dramatic appearance, packaging and utility advantages.
BODY STRUCTURE
The 2009 MDX utilizes the Advanced Compatibility Engineering™ (ACE™) body structure, which distributes collision forces through the structure during a frontal collision while helping to retain the integrity of the passenger compartment. The MDX uses a large amount of high-strength steel to help reduce vehicle weight while simultaneously increasing strength. Alternative materials including aluminum and magnesium are also used throughout the vehicle, further reducing vehicle mass, which helps improve fuel economy and increase performance.
Attaining a high level of dynamic body rigidity is essential for precise handling, ride quality and quietness inside the cabin. By researching the body's dynamic response to chassis loads resulting from everyday driving events, MDX engineers considered the unit body's "dynamic stiffness" as an entire system -- not just as a single component. Thus, body rigidity is not an end to itself, but rather it is an enabler for enhanced vehicle dynamics, riding comfort, and driving quietness.
Instrumented testing revealed that the "tailgate ring" - the open area surrounding the tailgate - is particularly important for handling, stability and ride. In the second generation MDX, this area has been markedly stiffened, providing the rear suspension with a more solid mounting and netting an improvement in handling precision. In addition, the MDX's floor frames are wider than before for improved packaging and rigidity.
HIGH-STRENGTH STEEL
The use of high-strength steel contributes to rigidity, excellent crashworthiness and light weight. High-strength steel is specified in different grades for use in different parts of the vehicle. Some unit body areas using this material include the roof arches, floor cross members, tailgate opening and front rails and body sides.
LIGHTWEIGHT ALUMINUM
In addition, about 4.1-percent of the 2009 MDX body components are constructed of aluminum. This material is ideal for certain components such as the hood and instrument panel support, where light weight is required but the strength of steel is not imperative.
The hood on the first-generation MDX was steel, and the weight savings of using aluminum instead of steel (for the 2009 MDX hood) is 15.5 pounds. Aside from using a unique metal conditioner and phosphate dip prior to painting, there are no unique production challenges for using an aluminum hood - and no ownership compromises either. To improve environmental efficiency, a factory separation line isolates different scrap materials, including aluminum, for recycling.
The aluminum instrument panel support saves an additional 10.5 pounds compared to a traditional steel unit. This support structure, which connects the A-pillars to the front floor crossmember, is a structural element consisting of cast parts, extrusions and sheet aluminum.
AERODYNAMICS
Acura MDX prototypes spent a total of seven weeks in the wind tunnel to test and develop its aerodynamic properties. The attention to detail in aerodynamic efficiency included the development of body side sills that help keep air from moving underneath the vehicle which can cause turbulence. Lift balance and the coefficient of lift were also addressed to keep the MDX stable at high speeds. In this area, internal testing revealed that the MDX exceeds the performance of the BMW X5.
WIND NOISE
Careful attention was paid to reducing wind noise inside the MDX cabin. An acoustic wind tunnel was used to identify and correct noise issues, resulting in the MDX's best-in-class wind noise performance (at the driver's ear point) according to Acura's internal measurements.
An added benefit of wind tunnel testing was the ability to rotate the MDX sideways into the airflow. This allowed engineers to approximate even the most severe gusting side winds and solve unexpected and unwanted wind noise that could accompany such severe conditions.
The MDX's moonroof is larger than used in the previous generation and is also the widest of any direct competitor. A finely tuned deflector ensures that the moonroof does not add objectionable wind noise when in the open position, even at highway speeds. Attention to detail in the sealing of the doors and tailgate also heightened the performance of the MDX's overall wind noise level.
INSULATION
Engineers attacked noise from virtually every source inside and outside the MDX. Their primary goal was to reduce noise at its source. One creative noise-reduction technique is the use of composite seals in the exterior door panels. These composite seals actually serve two purposes - to reduce the transmission of noise through the doors and to shield the interior components from dirt and water while driving through rain or puddles. The new door insulators provide a substantial reduction in objectionable sound - up to five decibels on some roads.
DOORS
The MDX's door handles are sized for comfort as well as ease of use, regardless of whether the user is bare handed or wearing winter gloves. There are three door checker - the detent mechanism that holds the door partially open - positions instead of the usual two, thus providing a convenient "in between" position useful during tight parking situations. The door openings are finished with an attractive composite garnish that hides the doorsill when the door is open.
GLASS
Normally only sports cars use windshields with highly compound curves. Deeply contoured glass is more complex and costly to make, thus it is usually reserved for low-production vehicles. Designers specified deeply curved acoustic glass for the MDX for its styling appeal as well as to improve aerodynamic efficiency and quietness. The 2009 MDX uses an acoustic glass front windshield that incorporates a unique PVB film to help quell wind and windshield wiper noise from entering the cabin. The rear glass is also a deep wraparound design - the deepest in the Acura product range.
The MDX has an auto up/down feature for the driver and front passenger's 3.5mm thick side windows. The 2009 MDX offers 273-degrees of outward visibility compared to 266-degrees of visibility for the BMW X5, which is a significant accomplishment considering the increased size of the MDX's head rests mandated by the government's FMVSS 202 safety regulations.
All glass from the B-pillar rearward has a gray tint to reduce eyestrain and heat buildup inside the cabin. In addition, the outside rearview mirrors use a special blue glass (sourced from Germany) that provides bright imaging along with excellent glare resistance.
XENON HID HEADLIGHTS
All 2009 Acura MDX models include Xenon high-intensity discharge (HID) low beam front headlights with halogen high beams. The advantages of HID headlamps include greater lighting power, daylight-color light balance and reduced power consumption. In addition, the cut lines of the new HID headlights are extremely precise, providing maximum nighttime visibility without distracting other drivers.
The 2009 MDX features Daytime Running Lights (DRL), which automatically turn on with the activation of the ignition. An MDX fit with the optional Sport Package features an auto-leveling feature that keeps the headlights level regardless of how the vehicle is loaded with passengers or cargo.
To ensure a high degree of theft prevention, the HID headlights are attached to the unit body with multi-strand steel cables. Halogen fog lamps are also included as standard equipment on all MDX trim levels
LED TAILLAMPS
Two Light-Emitting Diode (LED) arrays, comprised of 12 LEDs apiece, are used for the tail lamps of the 2009 MDX. Likewise, the Center High Mount Stop Lamp (CHMSL) features a single array of 16 LEDs. Advantages of the LED taillights include an elegant contemporary appearance, quicker turn-on time compared to a conventional incandescent bulbs and significantly greater service life. LEDs are also brighter, smaller, lighter and produce less heat than incandescent lights. The LED CHMSL was selected for its appearance and ability to produce the required lighting brightness while retaining slender physical dimensions. LEDs are also used in the MDX's outside mirror housing-mounted turn signals, improving visibility during lane changes or turns.
POWER TAILGATE
Acura's power tailgate system is included on MDX models optioned with Technology or Sport packages. The power tailgate can be operated via the remote key fob, from a button on the driver's door panel, or from a button located inside the tailgate. The location of the motor in the MDX's D-pillar (instead of in the roof) allows excellent headroom for the third-row seats. The tailgate can also be operated manually.
RESIN FUEL FILLER DOOR
The MDX fuel filler door is operated remotely from inside the vehicle via a switch on the driver's door panel. The fuel-filler door is made of a composite resin material that is lightweight, dent resistant and corrosion proof. For a better appearance the inside of the door features a flangeless resin design.
BUMPERS
The front and rear bumpers are constructed of a structural beam covered with a plastic fascia rated to withstand impacts of up to five mph without sustaining significant damage. An attachment point for a tow hook is located under a small cover on each bumper fascia. Removing the cover allows access to a threaded boss that accepts a steel eyebolt located in a holder in the jack storage area.
EXTERIOR PAINT
Inspired by the smooth finishes on fine pianos, Acura set out to achieve a mirror-smooth paint finish with a wet, glossy look. To advance the surface smoothness, "orange peel" - the finely undulating surface found on some paints resulting from the evaporation of the paint solvents - had to be all but eliminated. Seven environmentally safer waterborne exterior colors are available, and each uses a durable clear-coat finish that resists scratching and airborne pollutants. For 2009 the MDX is available with two new colors: Bali Blue Pearl and Mocha Metallic.
MANUFACTURING
Assembled in Alliston, Ontario, Canada, every 2009 MDX that comes down the assembly line goes through a special inspection area. Here inspectors focus on finding and solving any concerns. The inspection process is dynamic, with changeable parameters based on where concerns lie.
Along with the RDX, this represents the first time Acura vehicles are separated from Hondas during the assembly process. It represents Acura's commitment to being at the leading edge of quality and it is befitting of the most exclusive Acura SUV ever created.
2009 Acura MDX - Chassis
CHASSIS DEVELOPMENT
From its inception the MDX targeted the dynamics and driving feel of its strongest European competitors. The essential elements of this engineering goal included steering, suspension, braking and overall dynamic performance, as well as noise, vibration and harshness (NVH) control.
At the beginning of MDX development, engineers tested European luxury SUV competitors including the BMW X5, Mercedes-Benz ML350, Porsche Cayenne and Volvo XC90. These experiences provided real-world understanding of how these luxury SUVs functioned in everyday driving on their "home turf." Although later development testing was conducted in the United States, the DNA of the MDX was largely formed in Europe.
One essential tool that Acura used was the famed Nürburgring Nördschleife road circuit in Germany. This 13-mile course contains over 170 corners, numerous altitude changes and is considered the toughest natural road course in the world. Engineers used the Nürburgring as a "weakness finder" because it quickly exposes problems with a vehicle's dynamics, making them easier to identify and fix.
In order to build in a combination of increased handling agility, increased stability and comfort, the current MDX's wheelbase, tread width, and suspension technology were changed from the first-generation MDX. Engineers changed the lift and squat characteristics of the suspension to provide a flatter takeoff. Thanks to its extended wheelbase together with SH-AWD®, the 2009 MDX offers both exceptional high-speed stability and responsive handling.
FRONT SUSPENSION
The entire front chassis area was tuned to provide the best balance of handling precision, road isolation, and impact after-shake damping. MacPherson struts with inversely wound coil-over springs and forged-aluminum lower control arms reduce unsprung weight, while the front subframe "floats" on rubber mounts to provide road and engine isolation. The front suspension also uses newly developed hydro-compliance bushings to provide superior ride isolation as well as chassis vibration control. Suspension and engine mounts are specifically tuned to provide minimum vibration transfer to the occupants, and the front struts employ internal rebound springs to improve ride and handling. Anti-dive properties were revised to improve impact harshness and ride comfort.
REAR SUSPENSION
The MDX's rear suspension is a multi-link design mounted on a separate steel subframe. Squeeze-cast aluminum uprights (or "knuckles") reduce unsprung weight for improved response, while revised trailing-arm mounting points (compared to the previous MDX) reduce body squat during acceleration. Coil springs, dampers and an anti-roll bar are tuned for the optimum combination of ride and handling.
Rear subframe mounts and lateral control link bushing rates were significantly revised to create a discrete level of lateral force steer at the rear axle. Since the SH-AWD® system constantly varies drive torque at the rear axle, the longitudinal and lateral force steer properties were carefully developed for optimum response, stability and consistency.
ACTIVE DAMPER SYSTEM
Included with the optional Sport Package, the Active Damper System gives the MDX an elevated level of handling precision designed to satisfy the most discriminating drivers, while maintaining a smooth and controlled ride. Acura considered all of the available technologies before choosing electronically controlled, fast-acting Magneto-Rheological fluid dampers as the ideal technology to maximize ride comfort and handling in one integrated system.
The overall goal of the Active Damper System is to achieve outstanding levels of handling response while maintaining refined levels of ride comfort. This allows the driver intuitive vehicle control in a relaxed environment - free from neck straining head toss and other sudden vehicle motions. This is made possible by the quick response of the dampers and by the computer algorithms that keep the dampers a step ahead of the actual body movements.
Advantages of the Active Damper System include:
Flat cornering feel with minimal body roll or pitch -- even during spirited driving
Responsive, precise and secure steering feel
Elimination of unwanted under-damped body heave, roll and pitch motions
Improved tire adhesion, vehicle stability and road isolation
Real-Time Damper Control
The secret to the MDX's Active Damper System is its fast-acting shock absorbers. These dampers are built and tuned specifically for the MDX and offer the ability to individually adjust from minimum to maximum damping force in as little as five milliseconds (0.005 seconds). This ability hinges on the principle of electromagnetic induction. Each damper carries a unique coil that generates an electromagnetic field when current is passed through it. Proprietary damper fluid contains microscopic (on the order of 10 microns in diameter) ferric spheres that align when surrounded by the electromagnetic field, dramatically and instantly changing the effective fluid viscosity. Not only is the overall range of damping force available significantly more than that of a conventional damper, but there are hundreds of damping steps within that range.
The current that passes through the field coils is controlled by an electronic control unit (ECU) that uses special algorithms to determine the best damper setting for the road conditions. This, combined with nearly instantaneous reaction time of the dampers, allows damping control to occur before the vehicle's tires or body are allowed to have any extraneous motion.
The Active Damper System will operate with low damping when the road is smooth and level and the vehicle is being driven at a constant speed. Such limited damping further reduces the amount of vibration and harshness that passes from the suspension to the body thus quieting and improving the vehicle's ride quality.
Using the dampers' 5-millisecond response time, the Active Damper System reacts to sudden changes in driver or road inputs. The high damping force achieved in this short time allows the dampers to aid the springs and stabilizer bars in roll and pitch control, greatly improving the handling of the MDX.
The result of the improved transient handling, road isolation, and body control is that the MDX with the Active Damping System noticeably reduces the driver's workload when compared to other performance-oriented SUVs. The system is able to achieve the benefits of a sporty suspension without the traditional ride comfort tradeoffs. The overall benefit is more enjoyment, better control and less fatigue over the long haul.
Sport or Comfort Mode
The Active Damper System provides two driver-selectable settings - Sport and Comfort. Sport mode prioritizes handling response, vehicle body control and tire adhesion to allow for spirited driving with high levels of precision and composure. Comfort mode allows for a more relaxed driving experience by prioritizing road isolation and reduced passenger fatigue caused by road inputs. Either Sport or Comfort mode can be used in any type of operating conditions as preferred by the driver.
The Active Damper system maintains the same quality, durability and performance as all other Acura components, does not require any special maintenance and has no scheduled replacement interval.
POWER RACK & PINION STEERING
Of the luxury SUVs that Acura targeted in developing the MDX, the BMW X5 3.0i offered the best steering quality. Acura set out to exceed the BMW's combination of linearity, precise feel and security at high speed with using torque-sensing, variable power-assist rack-and-pinion steering.
Acura engineers spent considerable energy studying steering "on-center" feel in an effort to elevate the quality of steering feedback the driver receives. Beyond offering the correct steering effort level, the MDX provides subtle transient steering feedback that is an integral part of its subjective handling quality. Notable geometry changes include increasing the rake and trail over the previous MDX to provide a stronger steering feel.
WHEELS AND TIRES
The 2009 Acura MDX has standard 18x8-inch 5-spoke aluminum wheels with P255/55R18 104H M+S all-season tires. The tires were specially developed for the MDX by Bridgestone and Michelin and offer a significant traction improvement in dry and wet conditions, while maintaining the previous MDX's level of snow/ice traction. Michelin P275/45R19 summer tires are also available with the Acura accessory 19-inch aluminum alloy wheels.
Acura designers purposefully moved the wheels and tires to the high end of the competitive set. In 2009, the MDX has larger tires than all of its base-level AWD/4WD competitors and it is the only vehicle in the group with standard 18-inch tires.
4-WHEEL DISC BRAKES
The 4-wheel disc brakes on the 2009 MDX are the largest brake system ever featured on a production Acura vehicle. The brake system is engineered to provide best-in-class braking capability in dry conditions, as well as while driving in rain, snow or icy conditions.
Engineers benchmarked the existing MDX as well as the top competitors including BMW X5 and Porsche Cayenne for braking performance and pedal feel. The 2009 model has short pedal travel and firm pedal feel, in keeping with the direct feel that enthusiast drivers want. The ventilated front brake rotors are 13-inches in diameter with a thickness of 1.1-inches, wh
