Although most teams saved their main update packages for the next race in Spain - which marks the start of the European season - the huge rate of development in Formula 1 still meant teams were bolting on new parts in China.
As well as a number of outfits trying to get a grip on the F-Duct concept introduced by McLaren, we saw a number of tweaks to car floors, brakes - and even Red Bull Racing making some important tweaks to the nose section of its RB6.
More F-Duct developments
One of the main areas teams have been pushing quite hard in the early stages of the season has been with the F-Duct - the McLaren-pioneered system that is said to deliver a straightline speed advantage through reducing the drag of the rear wing at the driver's request.
We saw BMW-Sauber become the second team to race it in Malaysia, while Ferrari, Williams, and Mercedes GP all began trying out their versions in China for the first time. Only Mercedes GP kept its interpretation on its car for the whole weekend, but even then it was only an early trial.
I think there has been a lot of confusion about the actual extent of the benefit of the F-Duct though - I believe McLaren may only get a boost of between 3-5km/h.
I have heard people say that the F-Duct could be worth up to 10 km/h, but I think that is a bit ambitious. At a top speed of between 280-300km/h, the rear wing produces around 700 kilogrammes of downforce. The rear wing efficiency is about three-to-one , so that means you have around 230kg of drag - and 3kg of drag represents about 1km/h.
So to gain 10km/h you would need to lose about 30kg of drag - which equates to about 90kg of downforce.
The cockpit funnel for McLaren's F-Duct © Other
I don't think the McLaren system is losing as much as that, but now teams have started investigating different concepts anything is possible. The big advantage will come from allowing drivers to run with more downforce at lower speed. To do that, the team uses a more aggressive wing package for the slower corners, which will help the management of tyre temperature as well, but by using the F-Duct it won't compromise the car's straightline speed advantage.
From what we saw in China, it seems other teams are trying to pursue more passive versions of the F-Duct - instead of the McLaren route which requires the driver to close off the valve in the cockpit and help direct air onto the rear wing.
But introducing a passive version, which only kicks in at a certain speed, is not without its trouble. You would have to let it become active only above the top speed of the fastest corner of the track, otherwise there would be a danger of the rear wing stalling and losing downforce at exactly the moment you need it most - in the middle of a turn. And there are very few circuits where there aren't any high speed corners.
Mercedes' interpretation of the F-Duct © autosport.com
Mercedes GP, for example, is keeping its concept contained totally on the rear wing. On the leading edge of the main plane there is what is known as the separation point - where air decides whether it goes over or under the wing. The higher up the separation point, the more downforce the wing produces, this is because the air has to travel further and hence faster around the under-surface before it can converge at the trailing edge. But the air will only stay attached for so long and then it will stall.
If you can find where the separation point is, then you can put a slot there to take air into the internal column of the main plane of the wing - which is what Mercedes GP has done.
This air chamber is then connected via a duct on the upper surface to the internal column of the rear wing flap. This flap then has a slot in the rear under-surface which is a low pressure area - this surface can then suck on this slot and the air flow is fed from the leading edge slots.
In effect, this creates a three element rear wing - which will help create more downforce and help achieve tyre temperature earlier. And that is really what all the teams have been chasing.
Cooling the brakes
Force India was spotted doing something quite different from the other teams with its brakes in China, after mounting its calliper on the front edge of the wheel.
When it comes to mounting the calliper, the two locations where it is best to place them are, if we use a clock analogy, at 3pm and 9pm. This ensures the calliper is on the neutral axis of the assembly, because if you put it at 6pm or 12pm then you start picking up deflection in the upright assembly - which leads to brake knock off. You may need to stiffen up the assembly quite a lot if you did it this way.
Also, in the days of twin callipers they were mounted at 3pm and 9pm. On the rear wheels, the front calliper always cooled better than the rear one, while it was the other way around with the front brakes.
With modern brake ducting and uprights, it is critical to make sure the disc cooling is consistent throughout the race because of the high fuel loads at the start of the race. Disc temperatures can get up to 900 degrees centigrade, so if this is not kept under control, any parts of the car near them will overheat.
Having the calliper at the back of the upright means the air flow tends to go where the calliper is. Force India, though, has latched onto the fact that it can keep the brake disc temperature down by having the calliper at the front of the brake.
The view on mirrors
Force India's cockpu-mounted mirror © autosport.com
We talked a little bit about the mounting of mirrors in my column from the Australian and Malaysian Grands Prix, and Force India was the first team to pull them closer to the cockpit in China - as the FIA has demanded all teams do for the next race in Spain.
There has been a continuous debate in F1 about the location of mirrors - and for me it has missed the point because the two key considerations should be the mirror mounting system and the field of vision, not where they are positioned on the car.
The mounts should not vibrate and they must allow the driver to see clearly what is behind. Whether the mirrors are on the sidepod or the cockpit, if you can have a bad mirror mount it's no good for anybody.
The FIA has decided that the mirrors now all need to be moved to the cockpit sides, although given this year's narrow rear wings, having them mounted outboard was not the worst thing in the world. If the driver rotates his head, he can see across the rear tyre and have a wider field of vision. With them mounted inboard, the endplate is in line with the mirror and cuts off lateral vision.
Anyway, the rules have now been decided - and the designers will be working on how to minimise the aerodynamic problems caused by having the mirrors on the cockpit sides. There will undoubtedly be a small loss as anything sticking out of the car like that will have an impact - it's like sticking your hand out of the car window when travelling down the motorway.
There will be a penalty of turbulence, although it will be small - and I'm pretty sure in the overall picture of car performance it will be fairly negligible.
What is important to point out is that there was no actual aerodynamic benefit from mounting the mirrors on the sidepod, just less of a loss - all it does is get them out of the good airflow on the way to the rear wing.
The wake from the front tyres can be pretty bad, and the corner where the vertical turning vane and mirrors have been mounted is all about making sure the wake doesn't affect the air into the sidepod.
Over the first four races we have seen teams make a lot of tweaks to the front edge of their floors in the splitter area - and it is somewhere on the car that is becoming increasingly intricate.
Ferrari's old (top) and new (bottom) splitters © autosport.com
This area of the car is one that exists purely so teams fulfil the regulations. The reference plane has to start at the trailing edge of the front tyre and be between 300mm and 500mm wide, so in theory if you did not have this bit of the floor you couldn't have the raised chassis.
Had teams decided to use this part of the car purely for aerodynamic purposes then it would just be a fairly thin flat tray - however it has become a ballast carrier because that is the best way of getting the weight distribution as close to the front of the car as possible. In fact, it's the furthest forwards and lowest part of the car other than the front wing.
This part of the car will be carrying anything up to 35kg of ballast, and because of that it means the design has to feature some sort of section. Teams have to find aero solutions that manage this air flow, because this area of the floor is running at zero to 20mm from the ground. If it goes under this lip section it can cause increased pitch sensitivity.
That is why a lot of teams are using turning vanes and splitters to manage the airflow, so it doesn't spill off the sides of this lip too early. We saw last year after Malaysia that Brawn had developed a leading edge on the floor - and it has become an area of constant, if small development.
Once you change this part of the car, then it has an impact on everything else right through the car -so it's all about constant tweaking of the whole aerodynamic surfaces to get them all working together.
Red Bull gives RB6 new wings
I've said it many times before, and I will say it again - the design of the front wing is key for a modern Formula 1 car design.
The rest of the car will only work with the airflow that the front wing allows it to work with - 85% of the front downforce of the car is produced by the front wing. If you don't get good airflow off the front wing, then the rest of the car is not going to work. That is why if you take a snapshot of the Red Bull Racing front wing and the Virgin Racing one, you can work out why one car is at the front of the grid and one is at the back.
The front wing Red Bull used pre-China © autosport.com
At the Chinese Grand Prix, Red Bull Racing introduced a bit of a tidy up of its front wing - which will have created a whole new modified airflow regime over the rest of the car.
You can see that the top flap is tidier, with more constant curves. The team has still opted to stick with a multi-element design - well aware that if you have a two-piece wing then when you get a separation problem you can have a bigger issue trying to solve it.
With a three-piece wing, you can manage the airflow much better and Red Bull has gone a bit down the Renault route - with the vertical slot gaps where the flap assembly meets the end plates.
What Red Bull Racing has done to the front wing obviously has an impact on airflow over the rest of the car, and you can see that the team made further tweaks in China.
Underneath the nose section the team introduced some vertical turning vanes - similar to those Sauber has introduced. The idea here is that you want to get a turning moment for the air as early as possible once it is off the front wing and underneath the car - so it gets turned out onto the bargeboards.
You want the air to be introduced to the leading edge of the under-floor at as high a speed as possible. If the car is travelling at 200km/h, then all the complications at the front of the car will probably mean that the airflow is reaching the sidepod leading edge slower than the actual speed of the car. The diffuser can only do a certain amount of work on that airflow, but if you can get these turning vanes all working together and get the airflow to the leading edge of the side pods faster, then the diffuser will still do the same amount of work on that airflow but the end result is a lot more downforce from the underfloor.
What's in store for Spain
Every engineer in the pitlane will be eager to see how well their car improvements work in Barcelona, and I'm expecting a lot of tweaks up and down the pitlane.
As well as big upgrades from the new teams like Lotus and Virgin, there should be some fairly radical stuff at the front end of the grid too - with Mercedes GP pinning its hopes on a revised wheelbase to try and overcome the weight distribution and understeer problems that have dogged its start to the season.
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