Toyota Prius Prototype

Toyota Prius Prototype Review: “Has high body rigidity, even making the door sound better when closing” by Hideaki Kataoka

The official selling of the all-new Prius will start soon. The front mask of the fourth-generation Prius still remains the same with the previous-generation model, but its form has become bolder. It adopts a package with a low center of gravity like never before, and just like the Mirai, its design was filled with emotion and liveliness.

My impression of it has greatly changed when I sat in the car. It is because its hip point was made lower by 59mm compared to the previous generation model. Its steering wheel was changed from elliptical, which was its characteristic, into a circular shape. The tilt and telescopic steering wheel and driving seat that can be finely adjusted provide optimum driving position. Before embarking, I thought its field of vision became worse, but it actually had a great field of vision when I drove it. Since its nose became lower, its field of vision in the front and pillar areas became even better.

It still has the same hybrid system until now. Its 1.8L 2ZR-FXE Atkinson cycle engine is mated to a motor that adopts the THS II system. As for its engine, its combustion chamber’s air flow was optimized through the changes applied in its intake port and piston. It was also installed with a huge exhaust gas recirculation (EGR), which increases its combustion efficiency. It has best-in-class maximum thermal efficiency of 40% through its detailed improvements. Further, its motor, transaxle, power control unit and the like have become smaller and lighter in weight. As for its driving battery, it has a Li-ion battery in addition to NiMH battery. Including the NiMH, both these batteries are newly designed.

The seat positions became lower, and its atmosphere became sportier like never before. I felt that its seats became fitter than the previous generation model. I’ve heard that the spring characteristics in its seats were optimized and the thickness of its cushion pad and materials were also improved, but its holding was totally different when I drove this model. The level of comfort of its seats, including the rear seats, as well as its door’s sound when you close it have become better.

I’m grateful to have this opportunity of test driving the final prototype at the short course and within its nearby areas, but I also drove the previous-generation Prius and did a comparison test for it. As I expected, almost all of its parts have exceeded the previous generation model, and I found out its great progress. The first thing I noticed when I drove it was that it has a higher level of quietness. It doesn’t only have an extravagant soundproofing, its mechanical noises such as its motor parts were also reduced, and the range of driving in EV mode was also expanded. It also has better aerodynamic performance, so I thought its level of quietness tops its class. The operation sound of its cooling fan also has higher level of quietness that it makes me wonder.

Since its weight has become heavier, I thought it has no huge difference with the previous-generation model in terms of its acceleration performance in normal driving mode. However, it has sharp response and smooth performance, so it became more refined. It moved naturally when I switched driving from EV mode to engine mode, so I did not feel uneasy. The engine started so smoothly that it made me surprised. On the other hand, there were things I also did not notice while I was driving. It had a high RPM when I selected the power mode, but it wasn’t as exciting as I thought.

Its running performance has dramatically made progress. It surprisingly has high body rigidity, and it has better sound when you close its doors. Further, the shape of its suspension was also different. It still has front struts, but its rear part has a newly-equipped double wishbone suspension. I first test-drove the third-generation Prius, but I struggled a lot in controlling it while I was on the course. When I drove on the wet road, it was difficult for me to get to my target line. It had a slow steering response when I entered the corner, and I was troubled with its stubborn understeering. Its brake had issues, and I had difficulty in controlling it when driving at high speed. The car struggled when I stepped on the brake and it would falter halfway so its anti-skidding system was also fast.

On the other hand, the all-new Prius is controllable even if it is equipped with 15-inch tires. I was able to drive freely on my target line from the first corner. Its steering gear became quick and its rolling has been reduced, so I did not have any trouble in driving in continuous corners. Its linear steering feel and rear part was also accessible so I was able to drive easily towards my ideal line.

The Prius’s 215/55R17-sized tires also had an exclusive suspension. It has a solid body,and it has a high grip limit in addition to its wheels’ movement. Therefore, its flexibility was different when I drove at the same speed. It also had a wider controllable range so I was able to drive at ease on corners. I couldn’t find out a big difference in its handling whether in Li-ion battery mode or in NiMH battery mode. Its ride comfort, which was its weak point, has also improved. It has a gentle ride even when overcoming the bumps and protuberance. I’d also like to mention that it has fully-equipped advanced safety technology. Its Pre-Crash Safety System, which has a pedestrian detection function that uses milliwave radar and monocular camera, is highly reliable. The fourth-generation Prius is a more fascinating vehicle. I was not able to test its fuel consumption, so I want to check it when I can already test drive its production version.

â–  5 Star Rating
Packaging: ★★★★
Interior / Comfort: ★★★★
Power Source: ★★★★★
Footwork: ★★★★
Recommendation: ★★★★★

Hideaki Kataoka │ Automotive Journalist
A freelance automotive journalist who works as editor for a number of Automobile Specialist magazines. He has tried his hand at writing for a wide range of journals, and always provides deep incites into such subjects as EV and other cars with low fuel consumption and next generation automobiles. A member of Automotive Journalists Association of Japan (AJAJ).

(Translated by Claire Marie Sausora)