Sepang: three corners in detail
Turns 1 & 2
Turn 1 is a big engine braking zone, coming directly after the pit straight where the engine has been at full throttle for a touch under 11secs. The driver will brake down from 7th to 2nd gear and just 80kph for the entry of the turn before lightly applying the throttle between T1 and 2. At this point the engine needs to have good torque response as the revs drop to 9,000rpm. Renault Sport F1 engineers will do this through the pedal maps, giving enough sensitivity when the pedal is low.
Turns 5 & 6
Turns 5 and 6 are two of the fastest corners on the track, taken at an average 225kph, with only a small lift off between corners. The high speed changes of direction put the internals of the engine under a lot of pressure, particularly the oil system, where the fluids are ‘squashed’ to one side by the g-forces. In contrast to T1 and 2 where the pedal sensitivity is required is at low opening positions, the driver will mainly be modulating the pedal towards its maximum travels. The driver needs to have confidence in the torque and pedal maps at these high pedal positions, particularly over the curbs, to maximize his speeds through these two fast corners.
Top speed will peak at the end of the straight at around 310kph with DRS activated. Getting the right balance between a high top speed and appropriate acceleration is critical, making the choice of gear ratios crucial: you want to hit top speed just before the end of the straight to take advantage of greater acceleration. How the car behaves at this cruise speed will also be important for the driver. It needs to be smooth, so as not to affect the longitudinal acceleration of the vehicle. A smooth engine behaviour at the end of straight will ensure that reaching the top speed will be as transparent as possible for the driver and make overtaking easier. However, this can sometimes be difficult to calibrate, especially at Sepang where you have two long straights of opposite directions, which can mean that the wind can come into play.
Remi Taffin, Renault Sport F1 Head of Track Operations
After a successful weekend in Melbourne our attentions turn very quickly to Sepang. The 5.543km circuit is a challenge for the engine as a high percentage of the lap is spent at full throttle, plus there are two long straights of just under a kilometer each. On each of these straights the engine is at full throttle for over 10 seconds, thus requiring strong acceleration and top speed. The two straights however run in opposing directions, which we need to take into account when selecting seventh gear – if the wind is blowing down one straight, the acceleration can be compromised on the other one if the gear ratios are not correct.
There are also tight mid to low speed corners so the engine needs to be responsive on the apex and exit of turns. In particular, the first corner complex requires good stability under braking and response on pick-up as it leads onto a long, curved straight. Engineers will try to deliver the correct amount of overrun support here to help the driver on turn in so this exit is not compromised.
Of course the main characteristic of Sepang is the high ambient humidity. Even if the rain stays away, the high water content in the air displaces the oxygen available to burn, which slows the combustion process and reduces engine power output. If it rains – as we’ve seen every year so far – the challenge is to set the parameters to reduce power loss while still providing enough grip. Renault engineers will set the pedal maps appropriately for wet conditions to help the driver better modulate the torque application and will then monitor the on-car torque sensor to ensure the engine is always providing the torque requested. This is particularly important in the quick turns, and particularly the back section from turns 9 to 13.
Allied to the difficulty of the track, there is the challenge of how to manage the engine pool at the start of the season. Basically in Melbourne, we introduce the first engine with the aim to use it the entire weekend. Coming into Sepang, there are two options: either keep the first engine for the second consecutive entire weekend and have an engine with up to 1,600km at the end of the Sepang race, or introduce a second (fresh) engine for Saturday and Sunday in Sepang to avoid high mileage at the end of the race here. The second option gives us more flexibility to use the first engine as a Friday engine for longer. We know there will be mix of strategies at Sepang and this will give a bit of information on how teams evaluate this topic.