BoP changes behind hybrid Prius’s loss of SUPER GT form
An unfavourable Balance of Performance is the main reason that the hybrid-powered Toyota Prius has struggled so badly in SUPER GT so far this season, according to Yuhki Nakayama.
In its third year of service, the front-engined apr Prius PHV GR Sport GT300 driven by Nakayama and Koki Saga has failed to score a point in five races, the duo’s best result so far in 2021 having been 13th place last time out at Sugo.
Last year, the hybrid-powered #31 car achieved a best finish of fifth and scored pole position at Suzuka, but this year it has had to run with an extra 20kg as part of a weight increase for all cars built to the series’ own GT300 rules, on top of the 51kg penalty designed to cancel out the benefits of the hybrid system.
In addition, it has had its air restrictor reduced in size from 30.27mm to 29.67mm, although for this weekend’s Autopolis round this change has been reversed.
Nakayama, who is in his third season driving for apr, believes the changes have rendered the hybrid-powered Prius uncompetitive on all types of circuit, even compared to the sister #30 apr machine that runs without a hybrid system.
“The biggest problem is the BoP changed from last year,” Nakayama told Motorsport.com. “The car is heavier now so we are really struggling at technical circuits, and on tracks like Fuji with long straights, we are not fast either because the restrictor is smaller. We have much less performance last year.
“We are a little faster on the straights than the #30 [non-hybrid Prius], but the #30 is lighter than us, so they have much better cornering performance than us, and the tyres are different [Yokohama instead of Bridgestone].”
Nakayama also admitted the relative decline of the Bridgestone-shod GT300 teams in 2021 is having a negative effect on the #31 car’s performance.
“Dunlop and Yokohama have made a step in terms of performance this season,” he said. “All the tyre manufacturers are on a very similar level now, whereas last year Bridgestone had an advantage.”
While some Bridgestone teams have been able to gain an edge on the competition by making no-tyre change stops, Nakayama says the weight of the Prius - owing to its heavy 5.4-litre Lexus-derived V8 engine - makes that impossible.
“The engine is very heavy,” he said. “We used to use the V8 Super Formula engine, which was quite light, but now we have the same engine as the RC F, and it’s heavy, so we are struggling with that.
“Next season we really hope the BoP changes, because it’s too strict at the moment. But we also hope the experience we have gained this year with the development of the hybrid system will pay off with the results next year.”
The previous-generation Prius that apr campaigned until 2018, which utilised a mid-engine layout, was a regular contender at the front of the GT300 field, but a rule change forced the team to introduce the current front-engined car in 2019.
The last win for a Prius came at Sugo in 2016, with Saga sharing driving duties on that occasion with now-SARD Toyota GT500 regular Yuichi Nakayama.
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