The chief engineer for the Lexus RC F has explained why turbo power was rejected in favour of retaining a 5.0-litre V8 that is claimed to now have the fuel economy of a 4.2-litre while offering "much more" than 330kW of power.
Although rivals for the Lexus RC F, such as the forthcoming BMW M4 and next-generation C63 AMG will turn to turbo power, RC F chief engineer Yukihiko Yaguchi argues that “for a sports engine you want to give the emphasis to response characteristics” that only a naturally aspirated engine can provide.
Although Yaguchi-san understands that most sports cars are downsizing engine displacement and adding turbo power in order to achieve improved emissions, he explains how the revised 5.0-litre in the RC F can also achieve efficiency gains.
“We use the Atkinson cycle for the lower-speed travel and what that does is able to give us a fuel economy benefit and basically has the effect of reducing the engine by 800cc (0.8-litres).
“What we did put the emphasis on was to get the best possible fuel economy out of this vehicle during development.”
Lexus and parent company Toyota use the combustion technique known as Atkinson cycle on many of their engines including those employed by hybrids. The combustion method claims to reduce emissions, but also decreases power.
Increased power compared with the outgoing 311kW Lexus IS F is, however, teamed with a rev cut-out 500rpm higher, now 7300rpm, suggesting that engineers have overcome that lower-power trait. The new BMW M4 engine revs beyond 7500rpm with a turbo attached, though.
Yaguchi-san admitted he is trying to push the power output higher still, past 336kW.
“The final assessment of that is going to happen in the future so we don’t have that,” he tells. “The engine output is going to be at least 450 horsepower [336kW] and we’re trying to push that up even higher.
“We think that there’s more room to push it up.”
But Lexus US president Mark Templin admitted that “we could do [a turbocharged engine] in the future, there’s always a possibility for that.”
When Yaguchi-san was asked whether a more hardcore edition of the RC F could be created, he replied, “in the future we hope to maybe look at something like that”.
Neither the US boss nor chief engineer would name benchmarked competitors, nor Nurburgring lap times, though Templin made the bold claim that the RC F would beat its M3, Mercedes-Benz C63 AMG and Audi RS4 rivals overall.
“It may not be the fastest, it may not be the one that stops the fastest, it may not be a lot of things, but when you put all those things together I think you’ll find it’s the best driving car of the bunch”.