1986
Unrestricted turbo boost
Brabham, Williams, McLaren, Lotus
Regulation amendmentVerified — primary source
- Legal when raced
- Yes
- Closed
- 1989
- Survived
- 3 seasons
- Article
- —
What was exploited
Qualifying boost pressures around 5.5 bar producing a reported 1,400 to 1,500 hp, for one or two laps.
The gap in the rulebook
No boost ceiling existed in the regulations.
What it was worth
Qualifying pace unmatched before or since, at engine lives measured in single sessions.
How it was closed — Regulation amendment
A scalar ratchet rather than a single ban — 4.0 bar for 1987, 2.5 bar for 1988, then turbocharged engines banned outright for 1989.
Why it matters
The clearest example of a regulator tightening a number year over year rather than writing a prohibition. The register needs numeric series, not just ban dates, to represent it.