Remi Taffin, Director of Operations: "We've been extremely busy in the four weeks since the Hungarian Grand Prix. In contrast to the teams, who had to shut their factories, we've been operating throughout the summer break to continue our development programme. The dynos have run as usual and we've conducted some notable performance work for the rest of the season and also concepts for next year. The results are good.
"In parallel we have been preparing for Spa, which presents the hardest test of the year for the power units. The wide open throttle time is as high as Monza, but it's the corners, changes of altitude and length that increase the difficulty.
"We are realistic about the challenge facing us and the strength of the opposition at this point in time. The double podium in Hungary - and our win last year in Spa - show anything is possible so we go there in this frame of mind: concentrate on our job, do the best we can and take advantage of the circumstances as they come about."
Weather is always a factor in Spa, but rain can cause issues for the contemporary power units, which are loaded with electrical systems. If water enters, these systems could short out. F1 cars are now equipped with military spec wiring but special care will be taken to insulate the systems against the humidity, with ducts fitted to divert rain away from the systems in case of torrential rain. It's a useful precaution as it has rained in Spa every year since 2007!
Eau Rouge is the most famous turn on the Spa-Francorchamps circuit. It is technically more of a left hand kink in the track as it rises from La Source and crosses the Eau Rouge stream. A blind summit and a bump on the exit make it a fiendish challenge to get right. Eau Rouge is now taken flat out at 310kph but it took until the mid-point of the V8 era for cars to have the right power-to-grip ratio to floor it through the bend. At the start of the V8s and all through the V10s drivers would lift off to scrub some speed for the entry and apex.
While qualifying is significant in every race, the length of the circuit and the multiple overtaking opportunities do not place an over-arching importance on it in Spa. In fact only three polesitters have taken victory in the last ten years.
Spa is the hardest circuit of the year for the Power Units. Over 65% of the 7km track is spent flat out, which translates as around 73secs per lap, the longest accumulative wide open throttle time of the year.
The first period of sustained throttle is the climb from the La Source hairpin to the chicane at Les Combes. It takes around 25secs with the driver flat on the throttle throughout. The distance is only slighter shorter than a runway at Charles de Gaulle airport.
Almost all of sector three is taken flat out. From Stavelot through Blanchimont to the Bus Stop chicane, the Renault Energy F1 will be at wide open throttle for 20secs. The remainder of the throttle time comes from the bursts of power between corners.
The track's layout can be likened to a rollercoaster circuit where parts are loaded and unloaded in quick succession. The track drops over 40m from La Source before climbing over 80m back to Les Combes, equivalent to a gradient of 1 in 4. The descent compresses the internals but going over the crest of the hill, the vertical force is suddenly lifted and the parts unloaded, with the vertical forces switching to -3g. It can be equated to the feeling on a rollercoaster drop when your body feels compressed and pushed down into the seat but weightless when you go over a bump.
The altitude of Spa also affects fuel consumption. At its highest point the circuit is around 500m and the air is approximately 5% less oxygen rich than at sea level. With less oxygen going into the engine, around 1% less fuel is burned at Les Combes than at La Source.
Turbo response in Spa is one of the critical performance factors. The majority of slow corners, for example the Bus Stop chicane, Les Combes and La Source are followed by a burst of throttle. Engineers will therefore look specifically at the engine maps to bring the delay in response as close to zero as possible. In fact, the time lapse between the driver putting his foot on the throttle and the turbo kicking in is now around 0.2s
The turbo will be rotating at close to its maximum to keep pace with the high rotational speeds of the ICE. The altitude will further increase rpm. At its most extreme the turbo will be spinning at more than 95,000rpm or over 1,500 revs per second!
Spa is one of the most demanding tracks on the MGU-K. Each of the braking points comes after a long burst of power so the energy dissipated through the brakes is enormous.
The best opportunity for the MGU-K to recover energy is the Bus Stop chicane, which the driver approaches at over 300kph and brakes down to just 75kph.
At La Source, car speeds drop to just 70kph and engine revs to around 8,700rpm. The combination of MGU-K, ICE and brakes need to dissipate 2MJ of energy during this braking event - front brake temperatures will rise by more than 300°C to achieve this, even though the MGU-K is at the full recovery allowed by the regulations.
Sector two has the majority of corners and is therefore the least power sensitive part of the track. This pushes us to recover as much energy as possible on the MGU-H whilst maintaining good turbo response.
High-speed flowing corners such as Pouhon and Fagnes are the best opportunities and will feed the recovered energy to the MGU-K and ICE on the next period of throttle through Blanchimont.