Renault chassis technical director Nick Chester admits his team is surprised by the impressive gains Ferrari has made to its engine through the first part of the 2018 Formula One season.
It is now widely accepted that Ferrari has overtaken Mercedes as F1's leading power unit with the exact reasons for the Italian manufacturer's gains still unknown. Ferrari's impressive rate of improvement has allowed its customer teams, Haas and Sauber, to perform strongly during the first half of the season with Haas now just 16 points behind Renault in the race for fourth in the constructors' championship.
Chester admits Ferrari's surge in performance has taken the French squad by surprise.
"They definitely made a big step Canada-time, and I'd say yeah, we are a bit surprised," Chester said. "They've got a strong engine anyway, but it's really quite strong now. The performance is right up there.
"It does give us a concern. We're obviously in a pretty tight fight, so we've brought stuff all the way up to the shutdown. We're going to carry on bringing some aero developments after the shutdown, and it could be tight all year.
"We've got to work pretty hard, and even as we switch over to the 2019 car, anything that we can find in developing that that we can put back on this car, we'll try and do."
2019 will see the introduction of new aerodynamic regulations which sees the simplification of the front wing and modifications to the rear wing. When asked about Renault's development plans for the remainder of 2018 and when it plans to switch its focus to next season, Chester said: "A lot of the work is moving over to '19 now anyway, and it just depends what we find.
"Probably from now on, there will be a few more updates heading up to around Sochi or Suzuka time, and then after that, anything will probably be smaller, smaller parts that can come out of the wind tunnel program that comes in '19. We know we're going to have to keep going all year.
"We know we can't, really. We're going to have to develop. We've already got things in the pipeline that are going to hit after shutdown. Maybe when we get to sort of race 15, race 16, we can review it.
"But by then, most things will be in the process anyway for the end of the year. But it's just too tight. There is only points in it. An Austria result and you've wiped that out. So we've got to keep going and just keep pushing and getting the pace on the car."