Belgian GP Tech File Spa-Francorchamps is the most complete test of a Formula 1 car on the current calendar. It combines 320 kph straights with 70 kph hairpins, with several sixth-gear sweepers thrown in for good measure – and, of course, the unique challenge of Eau Rouge. While this section of the circuit and the fast left-hander at Blanchimont may no longer be as testing as they once were, corners such as Pouhon, taken blind in sixth gear, still allow the drivers to make the difference. And all of that is before you factor in the notoriously unpredictable weather in the Ardennes, which can see the circuit soaked at one end – and bone dry at the other.

Chassis

Spa is a severe test for a modern F1 car. The average lap speed is high, aerodynamic loadings are both elevated and prolonged, and every aspect of the vehicle's handling is tested to the limit.

The circuit features a high number of "aero corners" (only 6 of the 19 turns are taken at less than 150 kph), and this would normally push the teams towards relative high levels of downforce in order to maximise grip in the corners, as is the case at a circuit like Silverstone for example. However, Spa imposes a very different trade-off, because the two long flat-out "straights" on the circuit both provide genuine overtaking opportunities. This means that top-speed is a critical factor in order to protect position, and downforce levels must be determined accordingly. As a result, the teams run a similar aerodynamic configuration to that used in the North American races, achieving end of straight speeds of around 320 kph with the V8 engines (compared to 340 kph when we last raced at this circuit in 2005 with the V10). Aerodynamic efficiency (generating maximum downforce for minimum drag) is the key to success at this circuit.

In terms of suspension settings, the overall compromise is relatively stiff in order to ensure good aerodynamic performance in the quicker corners, and a good change of direction in the quick chicanes. However, good traction is also critical on the exit of the final chicane and La Source hairpin, as poor performance in either part of the circuit can leave a driver vulnerable to overtaking under braking for the next corner. Spa is the most demanding circuit of the season for the tyres, and it is no surprise that Bridgestone will bring the two hardest compounds from its 2007 range for this race.

Our ride heights are limited by the high forces encountered through the compression in Eau Rouge. From the bottom to the top of the hill, the car's ride height can vary by as much as 25 mm and if the car bottoms out too much, the drivers can lose control. With the V8 engines and the current aerodynamic regulations, Eau Rouge is now taken easily flat out at around 300 kph. The drivers will scrub off around 10 kph through the sequence, but it is important to conserve as much speed as possible in order to maintain position along the long straight before Les Combes.

Almost the only part of the car which has a relatively easy time is the braking system. The circuit features just three very heavy braking events, before turns 1, 5 and 18. Overall, though, this is one of the easiest circuits for the brakes owing to the numerous high speed corners.

Engine

Along with Monza, Spa is the most demanding circuit of the season for the new V8 engines, which have never been raced here. The test session earlier this year was an important one in order to verify the engine's operation around the long lap.

The duty cycle is particularly severe, with 73% of the lap spent at full throttle (only Monza exceeds this figure, with 77% of the lap). Furthermore, this includes two prolonged full throttle periods of over 20 seconds. The most challenging of these is undoubtedly the run of approximately 23 seconds from La Source to Les Combes, which includes Eau Rouge. This sequence exposes the engine and its ancillaries to extreme positive and negative vertical ‘g' forces through the compression and over the crest that follows. This is a factor we take into account when designing our lubrication systems, in order to avoid problems with oil feed under the extreme loadings.

Spa is also the longest lap of the season, and the circuit has a very high fuel mass penalty. Under the current qualifying regulations, this means that an engine with good fuel consumption can be a particular advantage.