Honda has confirmed that it had originally planned to introduce the latest major upgrade to its power unit at this weekend's Belgian Grand Prix, but admits it failed to meet that schedule.
The Japanese manufacturer is pushing its development schedule in order to satisfy partner McLaren and to prove that it can catch up with its rivals, in the hope of avoiding an embarrasing divorce which could see Honda exit Formula 1 at the end of the season.
As part of that development plan, the manufacturer introduced 'Spec 3' in Azerbaijan and hoped to introduce its next major step forward this weekend in Belgium, but Honda chief Yusuke Hasegawa admits they failed to do so and are therefore only running a partial upgrade.
"We had planned to introduce 'Spec 4' here but we failed, we didn't match our schedule," confirmed Hasegawa. "We're halfway through our upgrade so we called it 3.5 and 3.6."
Hasegawa is confident the partial update will deliver a performance boost, but says it would be difficult to tell how much because they're unable to make a direct comparison with the previous spec on the same circuit.
"It's difficult to compare the previous engine to this engine because it's a different circuit," he explained. "From the data point of view, we see a good update of the performance here."