James Allison takes us through the key differences to look out for between the team's 2018 challenger and its title-winning predecessor...
It's very rare for two Formula One siblings to be in the same room at the same time. But recently, our Technical Director James Allison gave us the chance to check out the W08 and the W09 side by side to see just how they compare.
The W08 is the older sibling and achieved a great deal of success during the 2017 F1 season, winning 12 races, securing the Constructors' and Drivers' Championships for the team.
The fresh-faced W09 has big shoes to fill and plenty to prove if it wants to match the success of its predecessor. The team has been hard at work for well over a year trying to improve the car, find more speed and tackle the regulation changes (which have been fairly minor, compared to the modifications for 2017) as best we can.
Sleepless nights, long days in the office, a relentless and exhausting cycle of development, all to try and find those extra tenths, hundredths and thousandths of a second that could be the difference between the top step of the podium and the next one down.
"It's completely impossible to do justice to the work of well over 1,000 people who have been on this project for well over a year, but I can show you a couple of the major things," explains James, stood between the W08 and W09. Not a bad place to be, at all!
"The biggest things by far that you are going to notice when you look at the new car are things that are made obvious by regulatory change. The one that strikes you as soon as you see the car is the Halo.
"This is a new rule for 2018 - a new piece of equipment - aimed at protecting the driver's head from incidents such as a tyre coming loose from another car and hitting the cockpit area at speed, something which would be a fatal event. So, very important for the driver's safety.
"A very, very big visual difference. Something which is an acquired taste and something which we will be working on in the seasons to come to try to make it more exciting to look at and also to offer more protection to the head of the driver."
Another of the more obvious rule changes is the removal of the shark fin engine cover and T-wing aero devices that sprung up in 2017. "Not the nicest looking things and something that was there almost as a regulatory accident," James admits.
"So, for this year, we tried to change the rules to get rid of those features." But, the shark fin hasn't been removed altogether. "The result is a much, much reduced fin on the back of the engine cover and no big T-wing," he adds. "That's the other big visual change."
Teams are always trying to package the rear of the car as tightly as possible, in order to improve the airflow around the car and generate more downforce in the crucial floor and diffuser area. "We have done an awful lot of work to make the car really, really slender," James explains. "If you compare it to the W08, you can see the difference. The bodywork bulges out more around where the engine and exhaust pack is.
"On the new car, this is much, much more slender. It doesn't look like much of a difference but, when you add it all up, that is something like a quarter of a second just there.
"It doesn't look like much but it was actually a huge amount of work from both the people in the engine department and over in the chassis side of the company. A lot of hair got lost in that project but the end result is something that is pretty to look at but, much more importantly, an awful lot quicker!"
A lot of the tweaks and changes to the car are tougher to see. You have to be really sharp-eyed to spot them. The W09 is very much an evolution of its older sibling, the W08, with the aim being to retain the key characteristics that made it the fastest car on the 2017 grid, while also ironing out any of the issues that brought the 'diva' nickname. These smaller modifications include the front suspension being raised.
"You need to be something of an anorak to really notice. But the front suspension looks quite a lot different to last year. The wishbones have been raised - something which has been a trend on F1 cars in the last few years," James adds. "This brings better aerodynamic performance. It is a big structural challenge but it is definitely something that brings you more downforce and a quicker car."
While the vast majority of the W09's changes are not clearly obvious and are small in isolation, they add up to something that makes a huge difference to the performance of an F1 car - even with evolutionary alterations to the technical rulebook.
"Last year's car was the quickest out there," James concludes. "It won more races than any other and was, of course, the Championship winner.
"But, it would be utterly hopeless and blown away by the W09, because of all the work by all those people over an entire year, making modifications at every level. All of them small, but all of them accumulating to a huge end result and a car that is much, much faster."
F1 cars made a big performance step in 2017 and were the fastest they've ever been. But, 2018 looks set to be even quicker, with lower lap times and new records to be broken this season. It's all exciting stuff - and we can't wait to see it in full-blooded action in Melbourne.