ENGINE TUNER wrote: The I4 was considered the best solution in the original turbo era, and if all layouts were allowed the I4 is what they would all converge upon(unless maybe the I3 would be a better solution). That is why the I4. Turbo because it is also the best and most efficient solution, but if they want some other type of forced induction that would be allowed.
The BMW I4 turbo won 9 races between 1982 and 1986.
In that time 89 races were run.
Cosworth V8 won 11 races in 1982 and 1983, and was only in lower teams from then on.
V6s won 59 races.
The BMW I4 continued in 1987, and was raced in 1987 and 1988 as the Megatron. That's 32 more races V6s won in those seasons.
Zakspeed raced an I4T from 1985 to 1988 with no success. Hart raced an I4T from 1981 to 1986 with no success.
Alfa Romeo ran a V8T with no success from 1983 to 1988 (1988 as Osella).
V6 turbos were raced by Renault, Ferrari, TAG, Honda, Ford (Cosworth), Motori Moderni