https://headlines.yahoo.co.jp/hl?a=2018 ... ports-moto
"We introduced the new specifications of power unit,there was no big problem basiclly and the performance was encouraging, but when we checked the details carefuly, we found that we still have some work to do before we used it in the race, so we switched back to the old spec power unit."Tanabe san said.
Although the spec3 power unit made great progress in terms of performance,the rpm of the engine during upshift was not smooth. It was still able to run,but honda decided to make some further adjustments to the control software and will not use it again this weekend.
"We already run it on friday,so its still able to run but cannot run well, considering the race distance,I think we still need to optimise it . We did a lot test on the dyno and then bring the new engine to the track, we expected that there would be some difference between dyno and track conditions, but when we actually ran, the difference was bigger than expectation."
Honda discussed with Toro Rosso side,Toro Rosso will send some engineers to HRD Milton Keynes to sovle the problem together,to make better perparation for Japanese GP.
"We will get some help from the team side, engineers from the team side will come to HRD Milton Keynes on Monday.We will do some dyno test with the new spec PU and gearbox,to have a better matching.”