 Complete the following phrase:  On 15 September 2017, it was announced that Toro Rosso would terminate Renaults remaining contract of customer engine partnership in order to sign the full-works Honda power unit partnership contract for 2018 onwards, after Honda had severed its ties with McLaren and thus Toro Rosso earned direct factory support from Honda as a flagship team. On the following day, the team confirmed that they would retain their final 2017 driver line-up into 2018, with Pierre Gasly and Brendon Hartley. During pre-season testing, many were surprised at the speed and reliability of the Honda engine, which had gained a poor reputation during the past three years with McLaren. However, the first race in 