The FW11B was the last Williams to race with a Honda engine, the Japanese company announcing during the season that they were moving to McLaren from , despite a year left to run in the contract with Williams. It was believed there were two main reasons for this. Honda were unhappy with Williams management for allegedly not honoring the number 1 status contract of 'their' driver Nelson Piquet. Honda (and Piquet) believed that Williams should have ordered Nigel Mansell to give way to Piquet during races, and that their failure to do so cost Piquet the 1986 Drivers' Championship, and almost cost him the 1987 championship (though had Piquet not won in 1987, Mansell still would have given the Japanese company its first Drivers' Championship). While Mansell would stay with Williams for 1988, Piquet had announced during practice for the Hungarian Grand Prix that he would be moving to Lotus in 1988 as their undisputed number 1 driver, thus also staying with Honda. The second rumored reason why Honda left Williams a year before the contract ended was the team's refusal to dump Nigel Mansell from the driver line up and replace him with Satoru Nakajima in 1986 (Nakajima made his F1 debut with Lotus in 1987). Team owner Frank Williams, always more interested in the Constructors Championship which saw the team as the champions, preferred to keep the experienced Mansell, not only as he was a proven race winner having won his first two Grands Prix near the end of , but he was more likely to score valuable points for the team. Williams was proven correct as Nakajima would race 5 full seasons in F1 with Lotus (1987-1989) and Tyrrell (1990-1991) and would only score a total of 16 points from 74 starts, with a best race finish of two 4th places. Another reason Mansell was retained was that he was under contract with the team until the end of 1988.