When it was launched in 2012, the CX-5 represented a monumental breakthrough as the first Mazda to feature SKYACTIV TECHNOLOGY and KODO Design. In developing of the all-new CX-5, the engineers in charge of driving dynamics strove to take the Jinba Ittai—“horse and rider as one”—driving experience of the new-generation lineup to the highest level possible. This meant developing a car that would provide not only drivers but also passengers with driving pleasure.
Kiyoshi Hayashi, deputy program manager, drafted the plans for the CX-5 development project including performance, weight and scheduling targets. He also led the development of driving dynamics as the coordinator of the engineering and testing and research departments under the Vehicle Development Division. As one who has devoted himself to car development, Hayashi is widely known. Rather than scheduling regular meetings, he communicated directly with each engineer and visited each department to promote co-creation. He placed importance on cabin quietness.
“When describing Jinba Ittai, we often use the word ‘responsive.’” But that doesn’t mean the car merely responds to the driver,” Hayashi said. “Our vision of Jinba Ittai also includes eliminating any vehicular behavior that drivers or passengers will find unsettling or unpleasant and providing a quiet environment that allows them to ride in comfort. In other words, improving the dynamic performance of the new CX-5 called for raising the quality of the ride a level or two for everyone in the car. One key to this is quietness.
Under Hayashi’s centralized leadership, Masahiro Awane was responsible for road noise. In approaching noise vibration harshness (NVH) development for the new-generation product lineup, their team established indices for “Interior Noise Balance.” They then set a “quiet zone” goal for the CX-5 for an extremely quiet cabin even when driving at highways speeds or on rough roads.
“It was a big challenge to get the NVH performance of the tires, suspension and body into the quiet zone,” Awane recalled. It involved almost every aspect of the car. It involved tens of thousands of parts. We previously pursued superior cabin quietness by searching for the sources of vibration and the paths along which noise traveled and resolved each issue by working with the staff members from the departments in charge of those parts. Aspiring to further raise this level of cabin quietness, the project team reviewed their prior approach and considered whether further improvements could be made.
It became an exhaustive effort to identify areas where there was still room for improvement in locations that had already been checked. For example, by using special tools to detect locations where vibrating air generated noise, the team discovered that the headliner vibrated slightly. Driving tests to measure the vibration characteristics of each location revealed that resonance peaked in the rear fender panels. These painstaking efforts at co-creativity among departments enabled the team to reach its “quiet zone” target for road noise with the new CX-5.
The development team that worked on enhancing the quality of the diesel engine also focused on noise. Since introducing the SKYACTIV-D diesel engines, Mazda has introduced technologies such as the Natural Sound Smoother and Natural Sound Frequency Control to reduce knocking for a more pleasing engine sound. Mazda has also eliminated its model and engine displacements hierarchies and introduced these new technologies on each model when it was updated.
“Working to improve quietness without regard to hierarchy resulted in a pleasing sound in all Mazda diesel engines regardless of the model,” said Toshio Matsubara, who led powertrain development on the CX-5. “So we had to raise the bar even higher. Expectations are always rising. But I believed that, in addition to a responsive, dependable performance feel, if the engine was quiet and harmonized with the car’s linear characteristics, we could give everyone in the vehicle—not just the driver—a comfortable, high-quality ambience in the cabin.”
Kiyoaki Iwata is a specialist in diesel engine sound and vibration characteristics. In addition to bringing greater stability and more precision to the control systems governing the engine knock reduction technologies on previous SKYACTIV-D engines, he investigated the paths by which knocks travel from their source to the locations in the cabin to which they radiate. By blocking and controlling noise in the body as well as engine components, he built what he calls, “A car that is not just quiet but whose pleasing, high-quality sound matches the smooth feel of the engine’s acceleration.”
This reflects the sensibility he has developed over the years. Iwata was once dispatched overseas and told he need not return until he found the answer to the problem he was assigned to solve. He took various locally produced diesel engines apart and spent hours researching the methods used on the engines to insulate against noise and suppress vibration.
The development team also worked to further improve the SKYACTIV-G 2.5 gasoline-powered engine, focusing on how the vehicle responds to the driver’s inputs for acceleration. If the vehicle’s response is sluggish when the driver steps gently on the accelerator to pull out smoothly, the driver steps on it more than necessary and the car accelerates suddenly. But if the car is simply made more responsive so that it will start moving faster, the driver may be anxious about stepping on the gas. The development team focused on achieving the right balance between response time and the strength of the response. Masayoshi Kanei, a member of the development team, concentrated on getting the right balance for everyday driving. He said he felt he contributed greatly to improving the ride in development of the new CX-5 engine, he said he wants to do even more to offer customers a satisfying driving experience.
Manabu Takagi worked on handling stability. From the start of development, he felt it necessary to enhance ride comfort to give customers a higher quality driving experience. Achieving a level of comfort that enables drivers as well as passengers to experience the pleasing sense of unity with the car is what makes it possible to achieve the high-quality driving dynamics only the new CX-5 can provide.
Once they received management’s approval, Takagi and the team focused on developing a suspension that responds to the driver in a smooth, linear fashion. The goal was to optimize the characteristics of the new hydraulic bushings at the rear of the front suspension’s lower arms as well as the specifications and mounting locations of the front coil springs to support the 10mm increase in the tread over the previous model. These efforts were intended to ensure that the suspension maintains proper geometry and the tires continue to grip the road without any bouncing or inconsistency in damper performance. The work demanded precision adjustments in 0.1millimeter increments.
“Even though a road surface may appear flat,” Takagi explained, “your car will often sway or bounce slightly as you drive over it. Feedback from the steering wheel and pedals allows the driver to sense the conditions, but the passengers sway back and forth and cannot fully relax. This can’t be called quality driving. We were determined to provide everyone in the car with a comfortable, relaxing ride on any road.”
The slightest difference in settings can completely change a car’s character, and there’s no way to ensure a given result. So, he makes it a habit to go to the test course and drive each prototype vehicle whenever he has the chance. Using his senses to assess the car’s performance he works to achieve a truly comfortable ride.
In this way, engineers from different departments worked together to enhance the quality of the drive of the all-new CX-5. They also achieved their lofty objective of, “Providing all cabin occupants and not only the driver with a higher level of comfort.” But they aren’t finished. A new starting line lies just ahead. The evolution of Mazda vehicles and the challenges Mazda’s engineers tackle are ongoing.