Mazda SKYACTIV technology have been around some 5 years now and although initially thought to be the name for just the powertrain, SKYACTIV actually encompasses much more and extend to the structural design, engineering, chassis and even the safety features. A key objective of SKYACTIV Technology has been to raise the efficiency of the vehicle and a primary approach has been to lower weight in all areas. Individual parts made lighter can operate more efficiently and a vehicle that is lighter requires less energy to achieve a desired speed, thus using less fuel.
When it was first introduced, 5 Mazda engineers won the 2011 Japan Society of Mechanical Engineers Medal for their work on a new 1.3 litre petrol engine which could achieve up to 30 kms/litre using Japan’s 10-15 consumption test cycle. A highlight of the technology was the increase of the compression ratio to 14.:1 – 40% higher than most engines – without knocking. This enabled a 15% fuel economy improvement which would allow for a range of up to 30 kms on a litre.
Very quickly after that, besides introducing an advanced turbodiesel engine (SKYACTIV-D), Mazda began to show how SKYACTIV Technology was applied to areas such as the transmission (SKYACTIV-DRIVE), body structure (SKYACTIV-BODY), and chassis (SKYACTIV-CHASSIS). For the domestic market, it also has SKYACTIV-HYBRID technology in a variant of the Mazda3.
Being related to each other, the various elements in the SKYACTIV Technology are now being integrated to enhance vehicle handling. This has led to a new generation of vehicle motion control technologies which are unified under SKYACTIV-VEHICLE DYNAMICS. With integrated control of the engine, transmission, chassis and body, Mazda engineers are able to enhance the car’s ‘Jinba Ittai’ feel – that sense of ‘connectedness’ between car and driver.
The first technology in the SKYACTIV-VEHICLE DYNAMICS series is G-Vectoring Control (GVC), which sounds like something from ‘Star Wars’! The concept of varying engine torque to influence the dynamics of the car was first used introduced by Porsche about 2 years ago. By varying the torque distribution to the rear wheels and selectively applying brake pressure to the individual wheels, it is possible to enhance driving dynamics and stability and keep the car on the chosen course. Other carmakers have also introduced torque-vectoring as a more advanced form of vehicle stability control.
However, Mazda’s SKYACTIV-VEHICLE DYNAMICS is the world’s first control system to vary engine torque in response to steering inputs in order to provide integrated control of lateral and longitudinal acceleration forces; until now, lateral and longitudinal acceleration (G) forces have been controlled separately. This optimizes the vertical load on each wheel for smooth and efficient vehicle motion. By optimizing the load on each tyre brings the movements of the car more in line with the driver’s intentions, reducing the need for steering corrections, including many that are made unconsciously.
GVC maximizes grip by focusing on the vertical load on the tyres. The moment the driver starts to turn the steering wheel, GVC controls engine drive torque to generate a deceleration G-force, thereby shifting load to the front wheels. This increases front-wheel tyre grip, enhancing the vehicle’s turn-in responsiveness. Thereafter, when the driver maintains a constant steering angle, GVC immediately recovers engine drive torque, which transfers load to the rear wheels, enhancing vehicle stability. This series of load transfers extracts much more grip from the front and rear tyres, improving vehicle responsiveness and stability according to the driver’s intentions.
It sounds complicated and certainly, without a computer, all the actions would not be possible because they must be done at lightning speed. So the computer has to be able to process numerous streams of data from sensors continuously and send signals to the engine to adjust its output. What’s important is that the driver does not need to do anything and just enjoy the drive.
You may think that GVC is for fast and sporty drivers but it actually has usefulness in everyday driving conditions too. In fact, Mazda says it benefits drivers of all skill levels in a wide range of situations: from low-speed urban motoring to highway driving, winding roads, and even emergency manoeuvres. In addition, GVC significantly improves handling and stability on wet, snowy and unpaved roads and in such conditions, its benefits are at their best.
GVC acts smoothly so that it is virtually unnoticeable. The reaction rate and amount of control is extremely subtle, with a reaction time from the moment the driver operates the steering wheel faster than a person can perceive, and the resulting deceleration force usually at or below 0.01 G. So the driver will still have a natural driving feel but Mazda says that there is quicker and more precise control than is possible for a human driver.
Another benefit which even passengers will appreciate is less swaying of the head and body during cornering. This is something which may not be apparent but as a car is driven over many corners, the head and body will move and although the discomfort may not be noticed, there will be a degree of fatigue which builds up.
GVC can reduce such stress on the body caused by such fatigue because the minor steering corrections that cause the body sway are greatly reduced, even at low speeds. And when you consider how many corners you will go through on even a short drive to the nearby grocery store, that’s a lot of stress the body will experience.
So on long-distance trips, a driver will have less fatigue and that not only makes the driving more pleasurable but also safer. It’s something not immediately apparent but will make driving a Mazda feel different in a way that the driver might not be able to understand.
In addition, it is a highly versatile system adaptable to vehicles of any class and drive type. Being a software control system, there is no weight increase due to the use of additional hardware components. The only requirements are a SKYACTIV engine, which allows precise control over torque output, and a SKYACTIV chassis.
During a media event in Japan recently, Mazda provided an opportunity to experience GVC which is available on the latest Mazda3. Two other generations of the same model were also provided for comparison at the Mine test course which used to be a public speedway that has been bought over by the company and turned into a R&D facility.
The GVC experience was done on a specific course with many turns to allow the effects of GVC to be felt. Speeds were low – between 30 and 40 km/h – which made differences in steering movements difficult to detect. Only on a constant-radius U-turn did it appear that, with GVC, there was less steering angle needed. It’s a very subtle thing but the car’s steering felt more precise, reducing the need for steering corrections. It would have been interesting to see how GVC reacts at faster speeds but probably for safety reasons, Mazda didn’t include such a test.
GVC is another step forward in achieving that responsiveness which enthusiasts appreciate. It follows on from what Takeo Moriuchi, Deputy Program Manager for the Mazda3, told me when I was testing the model for the first time in Australia 3 years ago. An engineer largely responsible for chassis tuning, he said that the ‘new thinking’ among Mazda engineers was that the responsiveness can be better but the abruptness of movements should be reduced. Through a combination of damping and suspension geometry (plus lowering the steering ratio), the car reacts quickly to lateral motions more progressively without yawing, so the occupants do not experience discomfort (especially in their upper body). So they have cleverly managed to provide the sportiness in the steering response that enthusiasts want but at the same time, the forces exerted on the body are not so sharp and people will not be complaining.
While some companies may have reserved GVC for high-end models, Mazda wants to offer it to all its customers as soon as possible. It is starting with the updated Mazda3 which has just gone on sale in Japan and within 6 months, the same model in other countries (including Malaysia) will also have GVC. The second model is likely to be the Mazda6 and then other models, including the SUVs and MPVs and probably the next-generation pick-up too.
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