Naoyuki Sakamoto gives C/D details about everything from engine design to chassis welds on the new hot hatch — and laughs at the assumption that the car’s AWD and RAV4 have something in common.
At the launch of the 2023 Toyota GR Corolla, we spent a few minutes with Toyota’s chief engineer on the project, Naoyuki Sakamoto, to learn some of the challenges in developing the car and what he thought made it likely to go in the right direction.
C/D: Everyone in the United States is very jealous of yaris GR. How long after Yaris, the team started gr corolla?
NS: In fact, we started developing the GR Corolla in 2018. So before Yaris, we studied it. I’d say we’re developing both cars almost at the same time.
The GR Corolla uses a three-cylinder engine. Was it designed for the Yaris and tuned, or was it planned for the original Corolla?
Corolla is using the Yaris engine, but to bring it to the U.S. market, we thought we would need more power, so we started making modifications to make that possible. Americans demand power.
That’s what we are. If horsepower is a goal, why stick with three cylinders? Is the four-cylinder turbocharging easier?
In fact, the compact engine is suitable for a sports car. The closer you can keep heavy parts near the center of gravity, the better it handles, so the lighter the engine will be better. A lighter car is better.
How much does the Circuit version weigh?
So to create more power, what did you do? You didn’t drill or stroke it, it was the same size as Yaris’s engine, but what, another 30 horses? And a three-cylinder needs a balance axis, right? And this is a dual camera?
Yes, 300, up from 268 hp. We have increased the pressure and to do that we need to reduce the reverse pressure. We need to move more fuel in, more emissions, and it creates high reverse pressure. And yes, a balanced axis, and double oranges, of course.
How do you keep things cool?
We did a lot of testing along the way, in the summer, in the winter. We opened the grille, you can see, it is very large compared to an ancient Corolla. Vents to guide air through. Even straws, we have a thin straw for slow speed, for rapid air movement, and another duct below opens at higher revs, to put more air into the engine.
Is the whole chassis and body different from the old Corolla?
The chassis is reinforced, adding 349 welds and adding 2.7 meters of fillings, more glue. The floor is different at the back from the warehouse, to make room for difference. We also move the battery from front to back for better weight distribution. The front fender is a piece, the rear extension is mounted with a latch. The carbon roof is only for GR. The doors are like an antique car. The suspension shape for the front uses a new connection point, higher than 15 mm to make the roll center of gravity higher and we have made it harder but also lighter, only in design.
And the GR-Four, AWD, is it a performance version of what customers will get, a RAV4?
[NS laughed and brought it to the AWD expert, who also laughed]. It is the GR system dedicated to this type of vehicle in the United States. It was developed through the races, from our race series. It will provide more acceleration control under different conditions.
Choose to use forged carbon fiber for the roof instead of woven carbon fiber because it helps reduce the price, or because it’s fashionable and new?
Are you tired of talking about this car?
Not! I’m excited about it. We built it with a lot of passion.