From: Paul S Winalski From: asj@maths.uq.oz.au (Alan Jones) From: sylvan@islandnet.com (Sylvan Smyth) pre-1950 to 1953: 1.5 liters if supercharged, 4.5 liters if normally- aspirated. Note that in 1952 and 1953 the FIA World Driver's Championship was held to Formula Two regulations, note Formula One. 1954 - 1960: 2 liters if normally-aspirated, 0.75 liters if supercharged. >1954 - 1960: 2 liters if normally-aspirated, 0.75 liters if >supercharged. Formula 1 was 2.5 litres. I think 2 litres was the formula 2 from which it was developed. Incidentally, in 1959 they shortened the race length, which made the Coopers competitive abd led to the current car design. 1961 - 1965: 1.5 liters, supercharging not allowed. 1965 - 1988: 3 liters if normally-aspirated, 1.5 liters if supercharged. There were also equivalency formulae for gas turbine engines and Wankel rotary engines. Until the late 1970s the supercharging option was not viable (robbed too much engine power), but turbocharger technology tipped the balance the other way. Lotus tried using the gas turbine option, but the different driving style required (you can't use a gas turbine for engine braking going into corners) meant that option didn't pan out. Nobody ever tried to use the Wankel rotary engine option of the equivalency formula. >1965 - 1988: 3 liters if normally-aspirated, 1.5 liters if >supercharged. That should be 1966-1985 after the 1.5 litre formula of 1961-1965. 1986: 1.5 liters supercharged only. 1987: 3.5 liters if normally-aspirated, 1.5 liters if supercharged with 4.0 bar maximum pressure. 1988: 3.5 liters if normally-aspirated, 1.5 liters if supercharged with 2.5 bar max. 1989 - 1994: 3.5 liters, supercharging and non-4-cycle-reciprocating- piston engines not allowed. 1995 - present: same as previous spec, but cylinder capacity reduced to 3 liters.