Yes they are behind a little, I don't think the gap is as large as it first appears but as we all know Red Bull are one of the few teams that are able to claw back time better than others. The sales of little cans probably helps a lot!
I think @burrito is right though, to blame the engine is easy to do but compared to Honda, Renault have moved mountains to improve the way they have. It's not always about total horsepower with these engines but the way they deliver and recharge their power and that I think is what took Renault the time to learn. Reliability as well of course is a factor.
The only other factor is both Massa and Verstappen changed to the Supersofts on their pitstop. This worked very well for them and allowed them to push pretty hard, so the picture is maybe not 100% clear.
However, Melbourne is not much of an aero circuit so we'll see how the cars (not just Red Bull) perform in China and Bahrain.
I think @burrito is right though, to blame the engine is easy to do but compared to Honda, Renault have moved mountains to improve the way they have. It's not always about total horsepower with these engines but the way they deliver and recharge their power and that I think is what took Renault the time to learn. Reliability as well of course is a factor.
The only other factor is both Massa and Verstappen changed to the Supersofts on their pitstop. This worked very well for them and allowed them to push pretty hard, so the picture is maybe not 100% clear.
However, Melbourne is not much of an aero circuit so we'll see how the cars (not just Red Bull) perform in China and Bahrain.