Nov 2015 - When the Mazda CX-9 made its world debut back in 2006, it was an epiphany: A midsize three-row crossover SUV that defied the conventional design cues and cumbersome driving experience expected of vehicles in its class.
With the new CX-9, engineers sought to instill driving dynamics befitting of a Mazda—agile handling, tight steering and a responsive, controllable powertrain. To do this, they found smart solutions to keep CX-9’s structure light, yet rigid, with SKYACTIV Technology. They developed a new turbocharged SKYACTIV-G 2.5T engine that delivers instant throttle response, class-leading torque and an estimated around 20-percent increase in fuel- efficiency, based on initial estimates of U.S. EPA testing cycles, making CX-9 among the most efficient vehicles in its class.
Introducing the Turbocharged SKYACTIV-G 2.5T Engine
Absolute control, absolutely. This is a hallmark of Jinba Ittai. When a driver puts his or her foot down on the accelerator, a vehicle should do what the driver expects, harmoniously working to find the right gear at the right engine rpm to deliver the performance called upon for a given situation.
Throughout the SKYACTIV engine series, Mazda has never focused on the numbers that appear in the catalog. Rather, Mazda aims to offer customers a combination of great performance in everyday driving situations and excellent fuel economy. And Mazda’s engine development philosophy is to offer these two factors by combining the right displacement with the simplest configuration of technologies, as best suits each class of vehicle.
Based on this philosophy, Mazda’s SKYACTIV engine family has delivered it promise of combined performance and fuel economy, and it continues to do so with the introduction of the new SKYACTIV-G 2.5T. But how did Mazda land upon the decision to create this new engine?When Mazda’s engineers set out to design a new engine specifically for CX-9, they looked at how drivers used their vehicles. Customers want effortless acceleration through bountiful torque delivery, so engineers developed the SKYACTIV-G 2.5T with enough power and torque to provide ample acceleration without having to hunt through the gears.
Customers also expect top-notch fuel economy—not just on a catalog label, but in the real world, too. Mazda had a clean sheet from which to design a new powerplant. A large- displacement, naturally aspirated engine could deliver instant performance, but it would lack fuel-efficiency. A small-displacement, naturally aspirated engine could deliver fuel- efficiency, but it would sacrifice a premium performance feel. Finally, turbocharged engines often promise both effortless acceleration and high fuel-efficiency, but oftentimes, in the real world, their efficiency is not much better than a larger-displacement engine. Turbocharged engines can also “lag” before their turbocharger spools up, creating a sluggish, disappointing driving sensation when power is called upon.
One piece of technology is Mazda’s Dynamic Pressure Turbo, the world’s first turbocharger with the ability to vary the degree of exhaust pulsation depending on engine speed. The system routes engine exhaust to the turbocharger’s turbine through smaller ports at low rpm. It works similarly to when one might place his or her thumb on a garden hose, creating a strong amount of pressure through a smaller outlet. This allows the turbocharger to spool up quickly, creating instant boost—up to 1.2 bar (17.4 psi) of pressure. When the engine is in the heart of its rev range, it opens up secondary valves, allowing for greater amounts of exhaust gas to pass through the turbocharger. The system is complemented by the 2.5-liter engine that already benefits from more torque at atmospheric pressure than a comparable 2.0-liter by virtue of its size.
Further assisting CX-9 to maximize turbocharger efficiency is a 4-3-1 exhaust. With this setup, the exhaust from the middle two cylinders (2 and 3) is joined into a single port, while the exhausts from the outer cylinders (1 and 4) each have their own ports. These three ports come together at the entrance to the turbocharger’s exhaust side, where there is always one exhaust pulse arriving every 180 degrees of crankshaft rotation. Not only does this very compact manifold keeps the exhaust pulses separate for maximum energy extraction, it also harnesses each exhaust pulse to suck the residual exhaust from the adjacent ports.
That only tells so much of the story. In order to increase fuel-efficiency, SKYACTIV-G 2.5T employs the efficient combustion of Mazda’s SKYACTIV-G 2.5-liter engine and marries it to a cooled exhaust gas recirculation (EGR) system, which helps prevent burning excessive amounts of fuel when the engine is running at higher temperatures. In many turbocharged cars, heat is controlled through adding more fuel to the combustion chamber; Mazda’s cooled EGR reduces the need for that.
The cooled EGR helps bring engine temperatures down from approximately 500 degrees C (932 F) to just over 100 degrees C (212 F), allowing SKYACTIV-G 2.5T to operate with a compression ratio of 10.5:1—one of the highest numbers of any gasoline-powered, turbocharged engine.
The net result: 310 lb-ft (420 N-m) of torque at a low 2,000 rpm and 250 horsepower at 5,000 rpm on 93-octane gasoline (227 horsepower on 87-octane gasoline). At 55 mph (88 km/h), a driver needs just 18 horsepower to maintain speed on flat roads with a front- wheel-drive model—a four-horsepower reduction versus the outgoing model, illustrating reduced friction in all parts of the driveline and enhanced aerodynamics.
Additionally, as an example of CX-9’s readily available power, in the outgoing CX-9, when a driver needed 90 horsepower at highway speeds, the vehicle would have to downshift from sixth to fourth gear. However, the new CX-9 can more quickly draw upon that power with faster, better-controlled throttle response and stay in sixth gear, allowing for a smoother operation and a greater sense of confidence.
Lightweight SKYACTIV Technology and NVH Refinement
All of Mazda’s sixth-generation vehicles were faced with the program objective of losing weight and increasing efficiency, which would go toward delivering a more engaging driving experience as well.
With CX-9, even including safety and rigidity goals, engineers far exceeded objectives—so much that 53 lbs. of sound-deadening mats were added back into the body in for reduced NVH, placing it among the quietest vehicles in its class. In all, the new CX-9 lost approximately 198 lbs. (90 kg) in front-wheel-drive configuration and approximately 287 lbs. (130 kg) when equipped with predictive i-ACTIV AWD.
The weight savings allowed Mazda engineers to increase window thickness to 4.8mm and rethink active noise-cancelling technologies, in addition to using simpler, more rigid parts, to reduce noise. At 62 mph (100 km/h), interior noise levels have been reduced by 12 percent from the previous model and road noise levels have been reduced by 2.0 dB.
Safety at the Forefront
Mazda has been a leader in building safer vehicles through several methods:
- Provide an optimum driving environment with well-positioned controls, easy-to-read instruments, minimal driver distractions and good visibility.
- i-ACTIVSENSE, which provides active safety features like Mazda Radar Cruise
- Control (MRCC) and Blind Spot Monitoring (BSM).
- Passive safety, which is designed to make the structure and onboard features such that they protect occupants in the case of an accident.
Mazda’s class-leading chassis dynamics and outstanding HMI technologies adhere toJinba Ittai, advancing the notion of purposeful technology that reduces clutter and improves the driving experience. A lighter, yet more rigid, chassis and straight load-path frame rails integrated into the unibody secure crash protection in the event of a collision and lighter weight improves braking performance with 12.6-inch (320mm) ventilated front disc brakes and 12.8-inch solid rear discs (325mm). Those brakes are unchanged in size from the previous model, but they now have approximately 198 fewer lbs. (90 kg) to halt.
CX-9’s i-ACTIVSENSE suite1 features new and notable safety features, including:
- Advanced Blind Spot Monitoring (ABSM): Employing a 24 GHz radar on each side of CX-9, ABSM can detect vehicles closing in from as much as 164 ft. (50m) away.
- Mazda Radar Cruise Control (MRCC): Operating at speeds between 30 km/h to 145 km/h (19 to 90 mph), MRCC uses millimeter wavelength radar to judge the relative speed and distance to the vehicle ahead. In accordance with the target speed set by the driver, the system automatically controls the engine and brakes to maintain the driver-selected vehicle speed and safer following distance, which is also adjustable by the driver. Because the driver does not need to operate the accelerator or brakes while using MRCC, the system relieves some of the burden on long drives. The radar sensor is capable of precise detection from a long distance, so its use allows the system to operate effectively in the rain, in backlit situations, and at night. It is also possible to turn off all of the system’s automatic functions and revert to conventional cruise control should road conditions make this more desirable.
- Lane-Keep Assist System (LAS) and Lane Departure Warning (LDW): Rather than keeping CX-9 centered in a lane between two lines as some systems do, which can cause an unnatural-feeling tug on the steering wheel, LAS, which is available in a Mazda for the first time in the U.S., helps ease CX-9 into turns. Meanwhile, LDW vibrates the steering wheel to warn drivers if they begin to stray from the lane. LAS will employ a progressive approach to assisting users to drive within lanes, but the system will deactivate after warning the driver if it senses he or she has taken his or her hand off the wheel.
- High Beam Control (HBC): HBC allows users to keep high beams on at all times, dipping them when necessary when a camera built into CX-9 detects headlights from oncoming vehicles or tail lights. The system automatically switches to low beams below 19 mph (30 km/h), when they are unnecessary.
- Smart City Brake Support (SCBS): Using an near-infrared sensor mounted to the windshield, SCBS operates between 2 and 19 mph (4 and 30 km/h) to apply the brakes in order to lessen the severity of an impending and inescapable collision at up to 20 ft. (6m).
- Distance Recognition Support System (DRSS) and Forward Obstruction Warning (FOW): Uses a millimeter wavelength radar to display the distance of CX-9 to the vehicle in front of it in a five-step display, encouraging the CX-9 driver to lessen his or her speed if necessary. If distance between vehicles decreases and evasive action is necessary, audible and visual Forward Obstruction Warning signals will indicate that evasive action is needed.
- Smart Brake Support (SBS): Operates at speeds above 9 mph (15 km/h) to automatically brake in the case of an impending collision.
i-ACTIV AWD Predicts Road Conditions for Maximum Stability
In 2013 when Mazda introduced its first full-SKYACTIV vehicle, CX-5, it also ushered in its i-ACTIV AWD system that could instantly recognize road conditions and adjust response accordingly. Mazda’s all-wheel-drive system in the previous CX-9 took approximately 10 factors into account, including on-road speed, engine rpm and wheel slip, among others. The information was then fed through the onboard computers that would modulate torque transfer between front and rear axles.
i-ACTIV AWD upped the ante, implementing a host of other sensors that were already integrated into vehicles for other functions and channeling the information they presented such as ambient temperature, steering wheel angle, longitudinal grip, brake fluid pressure and even windshield wiper movement. In all, i-ACTIV AWD brings 27 different sensors together to paint a picture of road conditions and direct torque to the rear wheel as necessary, predicting what the driver may face on a slick road in the winter or in heavy rain.
i-ACTIV AWD measures road conditions 200 times every second and can adjust power distribution to account for wheel slip even in dry conditions. It can even route power to limit understeer during spirited driving, sending as much as 50 percent of CX-9’s power to the rear wheels through Mazda’s proven six-speed SKYACTIV-DRIVE automatic transmission.
New CX-9 comes with a seven-inch or eight-inch MAZDA CONNECT touchscreen infotainment system standing front and center for connectivity needs with commander control knob. Using both touchscreen functions when parked and a center-mounted commander control knob when on the move, MAZDA CONNECT intuitively and safety control radio, phone, navigation, diagnostic and phone functions. MAZDA CONNECT also enables voice controls for many functions as well as five shortcut buttons around the commander control for selecting favorite radio channels or enabling specific functions.
The driver also has an available 4.6-inch, full-color TFT screen in the gauges for many of these information readouts in addition to Active Driving Display, a full-color head-up display projected onto the lower windshield for readouts from the navigation, cruise control and other functions.
In back, passengers have two 2.1-amp USB ports available for charging smartphones or tablets, each mounted in the outboard passenger armrests.
Together, the technologies allow an unfettered driving experience while still allowing for the needs and wants of today’s drivers and passengers.Last but not least is the new Bose premium audio system, which is designed to deliver outstanding clarity, image and range. The 12-speaker system—two additional speakers from the previous CX-9’s Bose premium audio system—was benchmarked against stereos from ultra-premium crossover utility vehicles using several different audio formats, including radio and both full and compressed digital formats.
The Bose system in CX-9 was designed to be able to take compressed audio formats— often the go-to for many people—and tailor the frequency ranges of the audio files to better-simulate how the music would sound at a concert, with precise imaging and robust quality. Bose sound engineers worked with Mazda’s development team to acoustically tune CX-9’s interior, even going so far to develop silk tweeter covers specifically for CX-9 to make sure sound travels the way it was meant to do so.