Fernando Alonso's brilliance in taking the Pouhon corner flat out for the first time in qualifying led to the energy deployment failure that cost him a place in Q3, Motorsport.com has learned.
After receiving a tow from teammate Stoffel Vandoorne at the beginning of his final effort in Q2, Alonso had looked set to deliver a laptime that would have been good enough to get through to the final top 10 shootout.
But between Turn 11 (the exit of Double Gauche) and Turn 12 (the entry of the Fagnes Chicane), Alonso received no extra energy deployment from his Honda power unit.
With a full deployment of energy worth around 160hp, Alonso claimed on the radio that he had lost half a second at that moment – which was enough for him to abort his lap.
The lack of energy was not the result of a failure on the car, but was instead caused by Honda's system not deploying when it was automatically expected to.
Motorsport.com has learned that this failure to deliver the energy was the result of Honda's system getting confused about where it was on the track.
Honda's deployment algorithm is calculated through major throttle input, with it basing its calculations of which corner it is at by major throttle inputs.
So when there is a lift of the throttle, for example, the system takes this into account and works out it must have gone through a corner.
When Alonso took Pouhon flat out – rather than lifting as he had done previously over the weekend – Honda's system did not realise he had already gone through the corner.
Thinking Alonso was still on the run from the Liege downhill corner, rather than on the straight between Turn 11/12, it did not deploy any more energy.
Honda F1 engine chief Yusuke Hasegawa has confirmed that the issue was related to the control system.
"We set a segment to when we have the deployment, and normally that segment is divided by the throttle," he said when asked by Motorsport.com.
"Sometimes a driver is making a different operation, so that makes the system confused and we didn't have deployment at some certain area."
Hasegawa later said that Honda would likely need to change its procedures to ensure there is no repeat incident.