Friday, 23 July 2010

F1 -- A Technical Season So Far

It’s the weekend of the German Grand Prix and we’re more than halfway through the Formula 1 season. So I thought it might be useful to talk a little about the technical developments on the cars so far this year -- an area which determines who wins and who loses.

An F1 car is never a fully developed vehicle. It’s a permanent prototype, continually evolving in the pursuit of performance within the restrictions laid down in regulations. Every year there are certain areas of car development which dominate the headlines. Last year double diffusers were the hot topic. This year F-ducts and blown diffusers are keeping the teams fully occupied.

To make a car go fast you need two main things. First it’s the engine, which provides the energy, of course. But these days all F1 engines are delivering pretty much the same power -- around 730bhp -- because they’ve been equalised in regulations. They’re also much more reliable than units of years ago because revs are limited to 18,000 rpm.

So if the teams are delivering much the same power, the way they gain performance advantage is through the design of the rest of the car. To deliver speed, you need to design it with high levels of “down force”. Quite simply, this is the ability of the car to be pushed onto the tarmac as it drives along. The car is forced down by the sheer force of fast air running over the bodywork during the lap. The more grip you have, the faster you can go, particularly around corners where most time is made. So at the very basic level, a racing car is an upside-down aeroplane wing.

Delivering down force is an intensive development process involving wind tunnels and specialist computer software to design the car parts. Teams have to factor in how air will flow from the point it first hits the car (at the front wing) -- to the way it exits the car (the rear wing and double diffuser). Air has to be carefully channelled around so that the car gets sucked down. What’s really tricky is that because air is a fluid, its impact on one area directly affects another so design is always a compromise. Also, cars don’t move through the air in one direction, they turn and all this affects aerodynamics.

As I’ve mentioned, two areas are dominating debate this season in F1. The F-duct is a very clever -- and rather simple -- mechanism to give cars greater speed in a straight line. Pioneered by McLaren, it is a device which “stalls” the rear wing down the fast straights. But why would you want to stall the rear wing? Well by reducing the effect of down force in a straight line, you reduce drag. Reducing drag makes the cars go faster.

How this works is this: a pipe is built into the car with a little opening on the front of the car. Air gets forced into this opening, and normally exits via a hole in the cockpit. But, when the driver blocks off this hole by literally sticking his knee over it on the straights, that air passes along the rest of the channel and through to the back of the car, exiting over the rear wing. This additional airflow reduces the rear wing’s aerodynamic properties at the point where you don’t really need it. Reducing the “push down” effect of the rear wing gives the car a little bit more speed, around 5 kilometres per hour. Most of the other teams have now adopted their own variation of this device, with varying levels of success. The beauty of it is that because it is operated by the driver, it does not break strict regulations. 

Another ingenious technique to make the cars go faster has been developed this year by Red Bull -- the “blown diffuser“. Most cars have had the exhausts coming out of the top of the bodywork at the back of the car. When you’ve got your foot hard on the throttle, hot air passes out of the exhaust at a fair lick itself. At the start of the season, Red Bull moved these exhausts much lower so that those fast, hot gases pass between the floor of the car and rear wheels. The reason is that this additional, faster airflow can be used to make the double diffuser device work even more effectively as a down force component. The double diffuser is that bit of bodywork which sits at the very back of the car, close to the ground. It looks like a black coloured upside down tray. It helps the back end of the car to stick to the track, therefore producing more speed through corners.

Red Bull have had the faster car this season and have dominated qualifying. For the first few races, the teams couldn’t figure out how they managed to achieve so much speed amid accusations of running illegal ride-height adjusting mechanisms (which proved not to be the case). It seems a big contributor to their speed has been the lower position of their engine exhausts. In fact Red Bull tried to fool their rivals by placing fake engine exhaust stickers on top of their bodywork, to try to hide their design. They are still very protective of it, as you’ll see on the grid on Sunday when Red Bull mechanics will crowd around the back of the car to try to stop other teams taking a close look. There’s a bit of bravado about that because the teams always have photographers taking detailed pictures of rivals' cars out on the track.

But the blown diffuser design creates additional problems. Those hot exhaust gases are leaving the engine at 900 Celsius -- nine times the boiling point of water. This heat passing so closely over the bodywork can damage it and this is something Michael Schumacher’s Mercedes team has experienced after adopting the blown diffuser on both cars. Red Bull have months of head-start in working on this so have figured out the best way to deal with the heat.

And Red Bull have another ingenious system working in conjunction with the blown diffuser, courtesy of their engine supplier Renault. Another problem with the blown diffuser is that when the driver lifts off the throttle, he also reduces the amount of hot gases coming out of the exhaust. This drop consequently causes a drop in down force at the back of the car because the blown diffuser isn’t being blown. A sudden lack of down force causes instability at the rear of the car. This happens at the worst time for a driver because he lifts off the throttle when entering a corner -- under braking and at exactly the time when you want the car to be most stable.

Red Bull have got round this problem with doing something called “retarding the ignition”. By making changes to the engine mapping, they are able to still have some fast gases coming out of the exhaust after the driver lifts off the throttle, ie when entering the corner. This improves stability at the back of the car for longer, meaning the car can carry greater speed through the corner. But it can only be used once generally because it can put a large strain on the engine, making it more prone to failure. So Red Bull -- and possibly the Renault team -- use ignition retardation on the most crucial lap of the weekend, the last lap of qualifying on the Saturday.

Thanks for reading and I hope this technical insight has provided a little clarity to this aspect of F1.

No comments:

Post a Comment