Nojiri is aiming to become the first driver to win three Japanese top single-seater titles in a row since Satoru Nakajima in 1986 this year, having established himself as the dominant driver of the past two seasons.
The Team Mugen star's title defence ostensibly got off to a positive start in last week's one and only pre-season test at Suzuka as he set the best time across the two days of running, a 1m35.955s, on Monday afternoon.
However, he concluded the second and final day of the test a lowly 16th following a rare crash at Turn 6.
Early feedback from drivers suggests that the SF23 has a much greater tendency to oversteer than its SF19 predecessor, the result of a radically revised aero package aimed at lowering downforce to improve raceability.
This shift in balance appears to have thrown Nojiri off his stride ahead of the opening race weekend at Fuji next month.
"In terms of car balance, it felt like there was an overwhelming lack of downforce," said Nojiri. "It’s not consistent at all. That wasn’t the case for my car last year. I never had to correct the steering [mid-corner].
"I want to get this year’s car to that level [of consistency], but looking at the aero map, I don’t think it will happen."
Asked if he felt there was room to further improve his laptime, Nojiri replied: "It’s difficult, as it was already 5pm when I set that time. If it had been an hour earlier, I think it would have been a low, mid 1m36s."
Nojiri's chief engineer Toshihiro Ichise said he felt the two-time champion's best lap came about as a result of the conditions at the time suiting the #1 car rather than any inherent performance advantage.
He explained that the track conditions when Nojiri's best lap was set induced understeer, helping to correct the balance that the Mugen driver had been struggling with previously.
"Cars struggling with oversteer tend to produce better times as the track conditions improve," Ichise told Motorsport.com's Japanese edition.
"When there are better conditions, such as in qualifying, the friction coefficient rises, and the rear tyres, which are wider than the fronts, are more affected and understeer tends to occur.
"At the end of the first day, everybody put on new tyres and the track conditions improved dramatically. Therefore the rear grip was comparatively better, and those cars like us that were struggling with oversteer entered the sweet spot and could set good times.
"However, there’s no way we are going to have conditions like that during race week. Temperatures will be higher, and the track conditions will be worse. It just so happened that when we set that time, the conditions were good for us."
