Mazda released the CX-3 at the end of February. Its Japanese specification has one 1.5L SkyActiv diesel engine (DE). This engine uses a technology that decreases the knocking sound in diesel engines. I asked Tsunehiro Mori, in charge person of the engine performance development department, about its features.
This mechanism decreases the knocking sound from the vibration in the engine through the Natural Sound Smoother, a small cylindrical metal part equipped inside the piston pin. They crafted it as the technology that would improve engine silence, when DE was developed as one of the SkyActiv series.
According to Mori, “The equipment produces more knocking sound if the engine vibration frequency is at 3.5kHz (kilohertz). Hence, we will create a vibration that will prevent the knocking sounds.” That was their starting point. However, the development did not progress because even a computer simulation could not clearly indicate from which part the engine vibration occurs.
Thus, they developed an equipment that can measure the vibration of each parts by making a hole in the engine block while operating the car. As a result of their experiment, they proved that the main cause of the knocking sound was the vibration from its connecting rod between the piston and crankshaft when it expands and contracts. “This measurement is a huge driving force to achieve practicality,” Mori stated, and they accelerated their development.
They also thought about where to incorporate the parts (Smoother) which would negate the vibration of the connecting rod. Consequently, they selected the piston pin which connects the connecting rod and piston. They inserted the optimized smoother in the cylindrical piston pin after analyzing its weight and form in the computer, and after pursuing more experiments, they implemented this technology.
According to Mori, the decrease in the knocking sounds is perceived clearly when slowly accelerating from 20 to 40 km/h. Furthermore, from the clattering sound, it now produces a pleasant sound, and according to them, the engine would sound more natural as the former sound is reduced. This improvement appeals to the senses, and it is a suitable technology for the company’s next generation technology group, the SkyActiv.
It is incorporated, as a set, with the i-ELOOP, an energy regenerating system for middle and high grade AT cars (Including 64,800 yen tax). One month after its release, 13% of the customers among the 10,000 initial orders of the CX-3 have selected this option.
(Translated by Claire Marie Sausora)