Honda not allowed to use tweak to its engine update in Japanese GP

Toro Rosso's engine partner wanted to make a change on Pierre Gasly's car after qualifying, during parc ferme conditions, to address the oscillations that are still occurring when shifting up through the gears with its updated engine.

Ahead of the grand prix, the FIA confirmed that Honda had changed the post shift ignition retard settings on the Toro Rosso.

Its written request to do so was approved by the FIA's technical delegate, Jo Bauer.

Honda contests that it was then informed on the grid that it needed to change back, but does not know why.

It is understood that Honda is considered to have not made the change specifically as it was requested, so was told to revert to the previous settings.

Official comment from the FIA is expected shortly but was not available at the time of writing.

Gasly had to alter the timing of his upshifts during the grand prix, in which he finished outside of the points in 11th after starting seventh.

Honda says the change did not limit the engine's performance in the race but wants more information on why the FIA changed its original decision.

"We submitted the parc ferme change request to the FIA," said Honda F1 technical director Toyoharu Tanabe.

"They approved it, that's why they issued the document.

"I need to find out exactly why they changed their decision; what was done by someone.

"We were surprised, because they said yes. Suddenly, on the grid, they said no.

"We need to respect the FIA's decision, so we didn't use it."

Tanabe said it was "hard to tell if they are big or small" changes but the fact the FIA initially said yes showed Honda was not trying to introduce a major performance differentiator.

The Toro Rosso drivers still reported better driveability, after the upgrade was introduced in practice last week in Russia but benched for the race weekend so Honda could work on some improvements.

Honda's upgrade played a key role in Brendon Hartley and Gasly qualifying sixth and seventh for its home race, even though it failed to score points due to a poor start and tyre problems for the two drivers respectively.

"From the performance point of view, we are happy," said Tanabe.

"The post-shift oscillations, maybe some torque delivery at low-RPM, we will assess the data from here and can improve for the next race."