The Belgian Grand Prix represents one of the hardest challenges of the year for engines. Over 70% of the 7.004km historic Spa-Francorchamps circuit in the heart of the Belgian Ardennes forest is spent at full throttle, giving the track the second highest power factor of the season after Monza. Outright power and top speed are therefore rewarded significantly more than at other circuits on the calendar.
Renault engines have won at the track six times, including last year when Sebastian Vettel won from pole position. The first win came in 1983 with Alain Prost (Renault) before Ayrton Senna (Lotus-Renault) took the win in 1985. Damon Hill (Williams) and Michael Schumacher (Benetton) then gave Renault consecutive wins from 1993 to 1995.
Over one lap the engine will have a total wide open throttle time of 43secs. There are two principle ‘straights’ — the first from Turn One, the La Source hairpin, through Eau Rouge and up to Les Combes on the Kemmel Straight. The RS27 engine will be at full throttle for 23secs on this section. The second long straight is from Stavelot to the Bus Stop chicane where the RS27 engine will be at max revs for 20secs.
The long straights mean almost 75% of the circuit is taken at maximum throttle. This is of course a marked contrast to the last event on the calendar in Hungary where only 55% of the lap was spent on the throttle. The emphasis placed on outright power and top speed is therefore over-arching as any increase in power will reduce lap time significantly. In fact, any gains will be twice as effective in reducing lap time as a low power sensitive circuit such as Monaco.
The changes of altitude over the lap — and between corners — put the internals of the engine, particularly the lubricant systems, under considerable pressure. The compression at the bottom of the 80m climb of Eau Rouge squashes the car to the track, putting it under a vertical load of +3g. The g-forces effectively squash the oil and fuel to the base of the car.
When the car goes over the crest of the Eau Rouge hill, the vertical load is suddenly reduced. The lubricants ‘rise’ within the system and away from the pumps, which therefore need to be ultra effective to avoid starvation.
The Belgian Grand Prix is notorious for its changeable weather, but also the climatic changes at different parts of the circuit. The driver could need more grip in one area of the circuit but a smooth engine in a wetter part of the track so compromise engine maps are created to give as much flexibility as possible.
Pundits always discuss the micro climates, but the elevation changes also create very different atmospheric pressures. The elevation will change by +/- 100m over the lap and local ambient pressure can vary by up to 12mbar. With less air going into the engine, less fuel will be burned so the engine could require 1% less fuel at the peak of the circuit than when at the lowest point.