Honda is continuing to improve its 2017 engine.
That is despite the fact that, according to the latest specialist media reports, the Japanese manufacturer and McLaren are now on the cusp of a split.
But Honda chief Yusuke Hasegawa told the Japanese source Sportiva that the marque made a clear step forward at Spa.
"We assume that the improvement was one tenth, but in fact it may have been more," he said.
"It is difficult to see because of the characteristics of Spa, but if we would have run it in Hungary, the result would have been different."
Hasegawa said the new specification seen in Belgium improved the torque of the engine at low speed.
"Although Spa is not a place where there are many low-speed corners, the eleventh place in qualifying shows the effect of ’specification 3.5’," he insisted.