Honda will run dyno tests on their new spec engine before making the call on whether to race it in Japan.
Although Pierre Gasly and Brendon Hartley both ran the new specification Honda engine during Friday’s practices in Russia, Toro Rosso and their engine partner opted to revert to the older engine on Saturday.
They made that decision after seeing some “unsuitable behaviour” from the power unit.
Honda will run tests on the new engine this week before deciding whether to run it in Japan.
“We need to evaluate the test data,” Honda F1 technical director Toyoharu Tanabe explained to Motorsport.com.
“We plan to have a dyno test with the new spec and then we will try to optimise our calibration.
“Then if the level of optimisation is suitable for the race application, we will decide yes or no [if we use it].”
Already the new specification engine has been applauded by Toro Rosso with Tanabe adding that Honda are pleased with improved power it offers.
He said: “The simple and easy one is power. We see some improvement as we expected. That’s the main item which we found this weekend with the new unit.
“We’re happy to introduce a new upgraded spec here for Friday. We’re not so happy we needed to change and step back the spec for Saturday and Sunday.
“We see some positive performance with the new spec. It’s actually a negative, but to us is a positive, [that] we found some areas we need to improve for race application.
“That’s why it’s 50/50!”