Ferrari technical director James Allison explains the thinking behind the 2015 car, including the decision to stick with pull-rod suspension.
Asked if the SF15-T is about innovation or merely an attempt to address the errors of the F14-T, he replies: "With all F1 cars, every year, they are trying to do the same thing; to put as much power on the road as possible, which means not only having a high level of power but to make that power deliverable by the driver in a nice, controllable way.
"To have a high level of downforce," he continues, "but again, not just absolute, peak downforce being well optimised but across the range of conditions the car is experiencing on track; corners, high winds, low winds and in straight lines, making that aerodynamic package deliver performance in a range of conditions.
"Then a suspension characteristic that allows the right compromise between the suppleness of the suspension over the road and the support of the aerodynamic platform on top. So you can deliver high downforce to the car but without having the tyre skip across the surface of the track.
"Those are the things you work on every year, and in particular, compared with last year when we clearly had an unacceptably large gap in our performance, we've tried to make sure that the weaknesses we particularly felt were noticeable, on the '14 car, were put right for the '15 car."
The car looks more slender and longer than the 2014 car, is this all down to the regulations or is it more about repackaging?
"All the cars are going to be more appealing this year, around the front, around the nose," he replies, "because, after a few years of trying I think we've finally found a regulation that gets what we wanted from a safety point of view but also doesn't create the unappealing features of the last few years.
"I think all the cars will look a lot prettier at the front," he continues, "and the Ferrari is nice in that regard.
"The back of the car however, is something that is noticeably different from the 2014 car. We have been successful in pulling the bodywork much tighter to all the stuff underneath the skin. That's involved a lot of work, not just in the windtunnel but also in the design part of the company. We tried to find radiator designs that were fundamentally more efficient; for every square centimetre of radiator we are able to extract more cooling this year than last, and therefore able to close the car down at the back as a consequence."
The SF15-T retains the pull-rod suspension system all round, which will surely raise a few eyebrows.
"Every year you set out which areas of the car you should put your effort in to try and improve them," he admits. "These are decisions that need to be taken quite carefully because when you make a choice of working on one point of the car, because you don't have infinite resources, you are effectively making the choice not to work on another. So when you decide what to work on you have to pick quite carefully the things you think are going to bring you the maximum amount of return for your effort.
"Push-rod or pull rod, on the front, it has pros and cons on either side. Pull-rod is probably harder to get light and stiff but it's probably a bit easier to get aerodynamic performance from it.
"It's swings and roundabouts, it's an area of the car that wasn't felt to be a problem on last year's car and therefore not an area that merited an investment of effort this time around."
Turning attention to the power unit, he said: "The power unit has, along with the rest of the car, been an area of extremely high effort to improve.
"We had a number of issues with last year's engine and power unit," he admits. "Early on in the season the power delivery was not particularly sophisticated and it was quite hard for the drivers to get the type of throttle response that they wanted. It improved a lot during the season and we have taken that a step further for the SF15-T.
"A definite weakness of last year's car was the amount of electrical energy we were able to recover from the turbo was not really good enough for producing competitive power levels during the race... one of the reasons our qualifying performance was relatively stronger compared to our race performance. We've tried to change the architecture of the engine to make it a better compromise between qualifying and race performance.
"Then, plain and simple horsepower," he continues. "An enormous amount of work has gone into all aspects of our combustion efficiency to try to make sure that in this fuel limited formula, where every team is only allowed to burn the same amount of fuel, that every single compression stroke, every single ignition stroke is extracting the maximum amount of horsepower and putting it on the road."
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