When the wind blows

Our theoretical look at the comparative speeds of leading cars from 100 years of GP racing,
Part 5: the arrival of forced induction and ground effects

Words: Mark Hughes. Photography: LAT

1972 Ferrari 312B2
Index figure: 211.3
Virtual lap time of the current Spa circuit: 2m 08.3s

The B2's advantage over the title-winning Lotus 72 was more apparent in qualifying — where the starting weight penalty of the flat-12's greater fuel load didn't apply — than in the races. Introduced the previous year, it was essentially Forghieri's 312B with 72-inspired aerodynamics from its wedgy body. The inboard rear suspension of 1971 was replaced by conventional outboard and the track was widened. Unreliability restricted Jacky Ickx to just one win.

1973 Lotus 72E
Index figure: 212.1
Virtual lap time of the current Spa circuit: 2m 07.5s

Into its fourth season, and with two world titles behind it, the 72 finally became the fastest car with its move from Firestone to Goodyear tyres. The characteristics of the new rubber suited Ronnie Peterson more than Emerson Fittipaldi.

1974 Ferrari 312B3
Index figure: 212.6
Virtual lap time of the current Spa circuit: 2m 07.0s

Recalled to the F1 team after a year in exile, Forghieri borrowed from his long-term 312T project to make a stop-gap B3 that took Niki Lauda to nine poles. Full-width bodywork increased downforce, while bringing weight forward lowered the polar moment of inertia, making it a more directionally responsive car.

1975 Ferrari 312T
Index figure: 212.7
Virtual lap time of the current Spa circuit: 2m 06.9s

This was the fuller interpretation of Forghieri's centred mass theme, taking the process one step further by using a transversely-mounted 'box. The c of g was lowered further by a more extreme use of maximum cross section for the cockpit/fuel tank area. This also allowed a short wheelbase, making the car yet more responsive.

1976 McLaren M23
Index figure: 211.5
Virtual lap time of the current Spa circuit: 2m 08.1s

Goodyear opting for yet-harder tyre compounds compromised the forward-biased weight distribution of the Ferrari more than the McLaren. As the Italian car took an age to get its rear tyres up to temperature, the M23 became the fastest car, helped along by special development DFVs that closed the power gap to Ferrari, and a six-speed 'box.

1977 Lotus 78
Index figure: 213.1
Virtual lap time of the current Spa circuit: 2m 06.4s

Ground effect arrives in F1, via sidepod-mounted venturis with sealing skirts; a big downforce leap for no drag penalty. The centre of aero pressure was too far forward with this particular design, meaning it had to run more rear wing than ideal to compensate, hurting its straight-line speed. Only the unreliability of Mario Andretti's DFVs cost it the title.

1978 Lotus 79
Index figure: 215.8
Virtual lap time of the current Spa circuit: 2m 03.4s

A refinement of the 78, with a more favourable centre of aero pressure, made for a devastating superiority over a field that was still largely non-ground effect. Andretti cruised to the title despite the car's inadequately cooled rear brakes and a monocoque that wasn't stiff enough for the aero loads. Michelin's entry the previous year had restarted the tyre war, making for at least as much lap-time gain as ground effects.

1979 Williams FW07
Index figure: 217.7
Virtual lap time of the current Spa circuit: 2m 01.7s

Patrick Head's refinement of the Lotus 79 ground-effect theme, with an appropriately stiff tub, made Williams into winners for the first time. Head put the rear brakes outboard, not only allowing them to cool properly but also freeing up an airflow-generating area behind the venturis.

1980 Williams FW07/7B
Index figure: 220.2
Virtual lap time of the current Spa circuit: 1m 59.1s

Detail development over the '79 car included longer sidepods that enclosed an area around the rear wheels, wider rear track, new rear-suspension geometry and carbon-fibre in the undersides of the chassis to stiffen it.

1981 Renault RE30
Index figure: 218.2
Virtual lap time of the current Spa circuit: 2m 01.2s

A ban on sliding skirts and the adoption of a 6cm minimum ride height forced the teams to run massively stiff suspension and hydraulically controlled suspensions that got around the rule out on the track, even though the cars were legal when stationary. Renault's turbo 1.5s had been getting faster each year since their debut in '77. The RE30's V6 turbo was giving around 600bhp in race trim.

1982 Renault RE3OB
Index figure: 221.5
Virtual lap time of the current Spa circuit: 1m 57.7s

The '81 car adopted new regulations that banned driver-actuated ride-height control. Stiffer suspension had to compensate in order to withstand ground-effect loads. Ran electronic fuel injection for the first time, though it proved disastrously unreliable. Rival BMW was one step further ahead with fully electronic control of ignition/fuel supply.

1983 Ferrari 126C3
Index figure: 220.4
Virtual lap time of the current Spa circuit: 1m 58.9s

Ferrari's first carbon-fibre chassis, following the lead of John Barnard's '81 McLaren. Built complying to new flat-bottom rules that outlawed ground effect from sidepods, restricting it to an area aft of the rear axle line, hence the increase in lap times. The car was a marriage of Forghieri's powerful turbo V6 and Harvey Postlethwaite's effective chassis.

1984 McLaren MP4/2
Index figure: 223.6
Virtual lap time of the current Spa circuit: 1m 55.5s

A ban on fuel stops and a stipulated maximum fuel allowance of 220 litres hugely rewarded the efficiency of the TAG-Porsche turbo V6 (750bhp in race trim). McLaren's John Barnard dictated the engine's layout, allowing it to be packaged within a very tightly waisted lower body, the 'coke bottle' profile of which made for big aero gains, accelerating the air to the lower rear wing as well as reducing flow spillage outside the wheels.

Estimated Spa-Francorchamps lap time 1972-1983

Laurence Pomeroy's performance index is a device for comparing the lap-time potential of grand prix cars from different eras. He made comparisons at tracks where GP cars ran on consecutive years and repeated the process for each year