The K7 Premier has topped the sales ranking in Kia for 3 consecutive months. The stunningly grand K7 Premier improves upon all the elements that made it comparable to the full-size luxury sedans, boasting a precisely crafted cabin, for a more premium experience behind the wheel. The K7 Premier adds an extra dose of excitement to the large-car segment with its premium refinements.
A chassis must provide the ideal balance between stiffness and controlled flex, in order to provide the optimum ride and handling. This is where the engineers shine.
Research Engineer Kim Eunil and Lee Heejung (Suspension Engineering Design Team 2), who developed the suspension, and Senior Research Engineer Jeon Jaehong(R&H Test Team 2), who enhanced ride comfort, talks the development process behind the K7 Premier.
Q. Tell us about the K7 Premier’s exceptional ride quality.
Jeon Jaehong: Its predecessor also offered great ride quality. Although it did feature a very dynamic drive, we focused on making the K7 Premier more ponderous and luxurious vehicle this time.
The ride quality normally associated with the vehicle’s response to bumps is a factor of the relatively low frequency bounce and rebound movements of the suspension system. We tried to make it dynamic and engaging, but with sturdiness.
Q. Firm and dynamic handling with ride comfort sounds too good to be true. How did you make this happen?
Jeon Jaehong: Stiff suspension reduces body roll at the expense of ride quality. So we used the new shock absorber that includes a Hydraulic Rebound Stopper (HRS), which works to provide a smoother ride over harsh surfaces.
Rebound Stopper is a suspension dampener that helps give better control and reduce vibration and overall shaking. While previous Rebound Stopper was made of plastic, the new HRS is made of elastic polymer material so that it absorbs shock more efficiently.
Kim Eunil: The primary purpose of the HRS is to absorb shock, but it is longer than a regular rebound stopper so it can improve roll characteristics. A longer stopper reduces rolling and damping relaxation.
Jeon Jaehong: Upgrading suspension systems is not very cost-effective. It means that it is hard to improve customer satisfaction compared to the amount of investment in it. However, we think the HRS will be worth it.
Q. How does the new suspension valve system improve ride quality?
Jeon Jaehong: The original base valve made too much noise and it needs improvement. So we used this Modular Valve System (MVS) for the K7 Premier. It features a lot of advantages.
The base valve controls the oil flow that results from the damping rod entering the cartridge and displacing the oil. The oil gives resistance, the valve calibrated to allow the oil to flow past it in differing amounts to regulate the amount of resistance in both bump and rebound.
Though we can’t eliminate the noise from the valve completely, the MVS has a spiral port that makes lower noise. This improves ride quality.
Kim Eunil: The MVS comprises several discs, and more discs increase hydraulic resistance and damping force. We could manage the damping force by changing the amount of the disc. After countless experiments, we decided to apply 12 discs (11 kinds) on the K7 Premier, compared to the previous K7 (10 discs, 7 kinds).
Lee Heejung: Another advantage of the MVS is that it makes it possible to fine-tune the valve array to fit precise application needs. Each disc is only 0.1~0.2mm thick, which makes it easier to manage the damping force in detail.
Q. Upgrading from its predecessor K7 must have been tricky.
Jeon Jaehong: It was hard to improve the ride quality of a front-wheel drive model because the weight of the engine and transmission are over the front wheels. Softer suspension has not enough rear grip, while stiff suspension deteriorates a vehicle’s comfort. On the other hand, a rear-wheel drive car has an ideal weight distribution.
This time we used bigger bushings for better ride quality, and the K7 Premier has gone through tons of test drives because the number of the disc or different types of ports can change the damping.
Q. Suspension designing sounds difficult. Did you have to cooperate with other departments?
Jeon Jaehong: We feel insecure right after the car release date. We listen to reviews as much as possible to check if the consumers fully understood our intent.
Kim Eunil: Usually strut bearings are used for better steering feel and our competitor already had filed a patent application on the product. So, we had to develop a new kind of strut bearing. We did so through collaborating with other departments. The success made us feel very fulfilled. That moment really is unforgettable.
Ride quality is very important when choosing a vehicle, yet it is a very subjective quality. So we had to please as many people as we can. The K7 wouldn’t have been this good without all the effort of the research engineers.