Wednesday's running was significant as it marked the first time all three GT500 manufacturers had shared a track in dry conditions at Fuji using the new-for-2023 carbon-neutral fuel.
Speculation was rife during the off-season regarding which manufacturer had gained a competitive edge with the new fuel, with drivers reporting a small loss of power compared to using regular gasoline.
Last year there was little to choose between the Nissan and Toyotas in the speed traps at Fuji, with both the Z and the GR Supra proving capable of breaching the 300km/h mark at certain stages, but the figures from Fuji on Wednesday appear to show Nissan with a small but clear advantage.
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The #24 Kondo Racing machine of Daiki Sasaki and Kohei Hirate was consistently the fastest of all in the GT500 class, recording a best speed of 299.1km/h in practice and improving that to 300.8km/h in the FCY practice session.
All four Nissans featured in the top five for the day, with only the #37 TOM'S Toyota of Giuliano Alesi and Ukyo Sasahara getting in among the quartet of Zs with a best of 298.3km/h, likewise set in FCY practice.
Honda's NSX-GT, which was the weakest car in a straight line last year, meanwhile only just breached the 295km/h mark with both the #100 Team Kunimitsu and the #17 Real Racing squads.
Best top speeds at Fuji in FP/FCY practice (unofficial):
| Pos. | No. | Car/Team | Top speed | Success weight |
|---|---|---|---|---|
| 1 | 24 | Nissan/Kondo Racing | 300.8km/h | |
| =2 | 37 | Toyota/TOM'S | 298.3km/h | 4kg |
| =2 | 23 | Nissan/NISMO | 298.3km/h | 42kg |
| 4 | 3 | Nissan/NISMO | 297.5km/h | 30kg |
| 5 | 1 | Nissan/Impul | 296.7km/h | 10kg |
| 6 | 36 | Toyota/TOM'S | 295.8km/h | |
| =7 | 100 | Honda/Kunimitsu | 295.0km/h | |
| =7 | 38 | Toyota/Cerumo | 295.0km/h | 12kg |
| =7 | 14 | Toyota/Rookie Racing | 295.0km/h | 16kg |
| =7 | 17 | Honda/Real Racing | 295.0km/h | 8kg |
| =11 | 19 | Toyota/Racing Project Bandoh | 294.2km/h | |
| =11 | 39 | Toyota/SARD | 294.2km/h | 6kg |
| =11 | 8 | Honda/ARTA | 294.2km/h | 22kg |
| 14 | 16 | Honda/ARTA | 292.6km/h | |
| 15 | 64 | Honda/Nakajima Racing | 291.8km/h | 2kg |
Perhaps worryingly for the opposition is the fact that the two NISMO Zs, the two heaviest cars in the field following their success in the wet at Okayama, were equal-second and fourth-fastest.
Nissan SUPER GT executive director Motohiro Matsumura feels that the real difference between the best Nissan and the best Toyota may be smaller than it appears, but acknowledged the marque's advantage.
"It looks like the Z is around one kilometre faster than the Supra," said Matsumura. "It can vary depending on the set-up, if they are running more wing or more rake, but compared to the top car in Toyota, it was still quite close to the top speed of Nissan.
"Both the drag and engine power look quite similar. Honda looks like it’s more of a ‘downforce car’, which is why there is more of a difference, but they are especially fast in sector two."
On why the Kondo car in particular was so fast, Matsumura pointed out that the two Michelin-shod NISMO cars carrying ballast blurs the picture somewhat when comparing to the #24, which runs on Yokohamas.
"The #23 car is carrying 42kg of success weight, and this impacts the speed through the final corner and therefore influences the top speed," he said.
"Also in testing at Suzuka, there was a 1km/h difference between the two cars, so the character of the tyre and the ride height may affect such things. The performance itself is quite similar."
Top speed at Fuji isn't the be all and end all - as proved by the fact it was Honda that took pole for the Golden Week classic despite facing a deficit of at least a few kilometres per hour to its rivals.
But for Toyota, which has traditionally relied on its prowess in a straight line to be competitive at Fuji, the Z's speed is more of a worry - suggesting that Nissan may have made a better transition to CNF than initially thought.
Conversely, Toyota was tipped to have gained the most (or more accurately, lost the least) with the new fuel. The fact the GR Supra now finds itself at a disadvantage to the Nissan in a straight line indicates otherwise.
TOM'S team director Jun Yamada, whose cars qualified sixth and 11th on Wednesday, was reluctant to go into any detail when quizzed about Toyota's apparently diminished straight-line performance.
"I can’t really say too much… we just have to do our best," Yamada said. "The Nissan is faster now."
However, Honda SUPER GT project leader Masahiro Saiki feels that Toyota pursuing a more downforce-orientated set-up concept with the GR Supra could be the reason behind it slipping down the speed charts.
"I think the performance with CNF has almost matched what we had with high-octane [gasoline], including the other manufacturers," said Saiki. "I think the set-up concept has an impact on the top speed.
"The top speed of Nissan and Honda hasn't changed much from last year, while I have the impression that Toyota has added more downforce. The difference in speed in qualifying was small, so I don't think it's so much the engine."
Additional reporting by Kenichiro Ebii
