The start procedure
Since launch control was banned for 2008, it’s been down to the driver to manipulate the clutch and throttle to gain the perfect start – albeit along the way being aided by a number of passive electronic systems. With the clutch controlled via two paddles on rotary sensors behind the steering wheel and the fly-by-wire throttle pedal, there can be no active intervention on the part of the ECU, simply a linear response between the driver controls and the clutch/throttle.
Preparation for the race start begins with the warm-up lap, with the driver being instructed to complete a number of burn-outs, and this brings the tyre and clutch up to operating temperature. Having the clutch at the right temperature is critical in order to have a consistent start, both for the friction qualities of the carbon clutch plates and the thermal expansion of the clutch plates moving the bite point. The team can monitor the clutch temperature from the telemetry system, via a simple infrared sensor pointed at the clutch.
The bite point is the other significant factor. Towards the end of the warm-up lap the driver will conduct a Bite Point Find (BPF), a process initiated from a button on the steering wheel, where the clutch is released and the electronics detect the drop in revs and the clutch position is recorded in the software. Clutch position is sensed by either LVDT or non-contact sensors. With this data the team may instruct the driver to alter clutch settings from the steering wheel to tailor the clutch paddles to the bite point position. On this lap the car’s electronic mappings are set to ‘Race Start’ mode, which is simply an amalgam of other settings controlled via one switch. So engine mixture, rpm limit, gearshift and pedal maps are all set to their optimum for the best start.
As the car arrives on its grid slot the car will be left in neutral until the final countdown to the start. The driver will then draw in both clutch paddles and select first gear, while also holding the revs at around 13,000 rpm. In the final moments before the start, both clutch paddles are partially released to a preset position, such as in line with the gearshift paddles, which moves the clutch to the bite point.
To initiate the start the driver will release one clutch paddle, which releases the clutch part way between the bite point and fully released, and they can now modulate the throttle to manage wheelspin or avoid stalling. Bogging down off the start or stalling is prevented by an anti-stall system, an electronic process that detects the drop in revs and automatically pulls in the clutch and raises revs. Once the car is moving and wheelspin has subsided, the second clutch paddle is released and the clutch is fully engaged, with full engine power passing into the transmission.
Despite its low-rpm torque from the electric motor, the additional 80 hp KERS power cannot be used at the start. Only once the car reaches 100 kph is KERS allowed to be deployed, and it will be fully charged either from recharging in the pit or from harvesting power around the parade laps. The driver may use this tactically into the first turn or for other strategic points around the track to either defend or attack for position.
Also, around the lap the driver needs to reset the Race Start mode switch on the steering wheel to return to the individual controls on the steering wheel for powertrain set-up.
Fig. 1 - For its all its complexity, the start process relies on a pair of fingers on the clutch paddles (Photo: Craig Scarborough)
Written by Craig Scarborough