After trialling Honda's upgraded power unit during Friday practice in Sochi, Toro Rosso has opted to return to the older specification. Both Pierre Gasly and Brendon Hartley fitted the new engine to the car prior to the weekend, with Honda reporting an "encouraging" boost.
Gasly managed to finish in eighth place after the second practice session on Friday. However, the Red Bull junior squad has now decided to revert back to the previous engine specification. Honda will fit the new engine in again next weekend for its home race in Japan.
"Having studied all available power unit data after FP2, we realised that, although the performance was encouraging, there is still some work to do in some areas such as calibration and matching the power unit to the chassis,” said Honda chief Toyoharu Tanabe.
"So we have decided to revert to the older specification power unit on both cars for the rest of the weekend. We believe we can complete the work before the Japanese Grand Prix, so that we can run the new specification power units on both cars from then on.”