I remember an early 1978 argument over the chassis of the RS10 and the use of the engine,” said Renault Formula 1 team driver Jean-Pierre Jabouille. “Whether to put a twin turbo in it and modify the chassis to a ground-effect car. I thought ground-effect was obvious because Lotus were doing it already. Some people in the aerodynamics department at Renault Sport thought we could achieve greater efficiency going out of the corners, but there were others who were against the twin turbo and the ground-effect system.

“I was in favour of a ground-effect car with twin turbos,” Jabouille added, “but some were not convinced. So we made a ground-effect car with a single turbo. I was certain that it wasn’t a good idea after I had run a race with a single turbo and ground-effect. I wanted a twin turbo with the ground-effect car.”

The idea of twin turbochargers dated at least to May 1978, when team chief Jean Sage and sponsor François Guiter were chatting in the Zolder, Belgium paddock with Porsche racer Rolf Stommelen before that country’s grand prix. “Why doesn’t Renault use twin turbos?” said the German driver. “It would considerably improve the response time.”

“The twin turbo and ground effect were super-efficient”

This was a timely tip by Stommelen, who had been racing Porsche’s Type 935/77 during the previous season, its first with twin KKK turbos. By virtue of its flat-opposed six-cylinder engine the 935 was well adapted to a separate complete system for each side, including dedicated wastegates. The direct effect was that two turbos were substantially smaller in diameter than one carrying the same total exhaust flow, hence had much less rotational inertia to overcome when speed changes were demanded. This was the pattern now followed by Renault, requiring a tear-up of the rear of newcomer Michel Têtu’s new RS10.

The result was a symmetrical, compact and aerodynamically effective arrangement of exhaust pipes, turbochargers, intercoolers and induction systems. They also had short inlet and exhaust tracts, now having a separate small plenum log for each bank of cylinders instead of the previous shared plenum. Individual exhaust pipes were kept far apart and came together only immediately before the turbine housing. In this way, the imparted exhaust-flow energy was exploited individually and to the full.

“The first comparative tests of the twin turbo in the car took place at Dijon,” wrote Roy Smith in his book Alpine & Renault: The Development of the Revolutionary Turbo F1 Car 1968 to 1979, “on a private track equipped with chicanes to demonstrate the differences between the two solutions of behaviour in acceleration and response time. Every possible version was tested and compared with the original single-turbo set-up. The twin-turbo versions provided results which clearly favoured this type of installation compared with the single-turbo version.” KKK’s 3070GD turbos were fitted, revving as high at 150,000rpm against the single charger’s maximum of 80,000.

With intermittent flow created by opening and closing the wastegates, each turbocharger was powered not only by the mean pressure built up before the turbine but also by regular pressure peaks which imparted additional thrust to the turbine. “Gradually,” summed up Jabouille, “it became clear that both the twin turbo and the ground effect were super-efficient. Though the new engine was no more powerful it was much less brutal. The throttle pick-up came in at 5500-6000rpm instead of 6500-7000.

“From that moment on René Arnoux” – who joined to drive the team’s second car – “and I were very soon winning races,” said Jabouille. He and Renault knew Arnoux well from their Formula 2 battles, in which the newcomer was champion in 1977. But the 1979 Monaco debut of the twin turbo was less than a success with one car out after a collision and the other not classified.

Before the next race at Dijon-Prenois the track hosted a tyre-test session, during which Renault subjected one car to a simulation of the 189-mile race. A speed trap was set up on its one long straight. “I’ll never forget it,” recalled an engineer who was watching its readout when a Renault swept by. “Suddenly it showed a speed 20mph faster than anything we’d seen before. The Renault was coming good. Soon we would all need turbos!”

This was not a false dawn. In 1979 the V6 was running at 2.0 bar pressure on a 7.0:1 compression ratio. Approaching 11,000rpm it offered in excess of 600bhp, whereas the naturally aspirated cars were struggling to exceed 525bhp. In the French Grand Prix on 1 July Jabouille shattered the lap record to take pole position with Arnoux alongside in the front row. Making strategic use of his soft-compound Michelins, he took the lead on the 47th of 80 laps. Behind him Arnoux soon engaged the Ferrari of Gilles Villeneuve, who prevailed at the finish by a quarter of a second, taking third to Jabouille’s victory.

This was, as Niki Lauda put it, “a singular triumph for France since it happened to be the French Grand Prix at Dijon, won by an all-French car with a French driver at the wheel. The date to remember as the real beginning of the turbo era is July 1, 1979.” This was the high point of a season in which the team fashioned a scant eight finishes from 28 starts. Only two second places in Britain and America were otherwise of note.

“The 1979 French GP is the real beginning of the turbo era”

Having seen the potential of turbocharging at Dijon, rivals were arming themselves accordingly. The company with the lozenge badge had a head start that it needed to exploit. Hence it accorded great weight to the 1980 season, for which a much-modified car was built: the RE20.

“I thought winning the title in 1980 was realistic,” reflected engine designer François Castaing. “But I was having arguments in private with Gérard Larrousse [competition manager]. We already had Alain Prost under contract and we could have had him replace Jabouille for 1980. I was arguing that keeping Jean-Pierre was attaching a weight to our foot because he was not a potential champion in any sense. Larrousse was saying, ‘No, we have time to do that later.’” Castaing headed for the exit – a Renault job in America.

Renault would continue as a top-level team without winning either the drivers’ or manufacturers’ championships. It would field Prost from 1981 to 1983, coming close to titles in the last two seasons but falling short through chronic unreliability. “We were alone,” mused Bernard Dudot –  technical director. “A new team with a new concept, new tyre technology from Michelin and doing everything ourselves. Only Ferrari was doing this and they had a big history.”

“The engine was always the main asset,” added aerodynamicist Jean-Claude Migeot. “We lacked a chassis culture. There were a lot of good people but we weren’t properly equipped. Renault in those days would never have committed to a moving-ground wind tunnel – and that’s what was required.”

A heavy dependence on outside suppliers for crucial components was also an issue – especially when incoming inspection was not rigorous enough. It was difficult to convince their suppliers of the demanding nature of this new kind of French engine. Nor were internal priorities always in balance. “By 1980 the car was very competitive for qualifying, for one lap,” said Arnoux. “I won in Brazil and South Africa but after these races we had a lot of problems, breaking engines for different reasons.

“Some people in the team said, ‘Oh, we are not lucky,’” added Arnoux. “That was a very bad analysis. We were not lucky because we didn’t work in a good way. Maybe with less power but more reliability we had the possibility to win the championship. We had a very strong man who developed the engine [Dudot]. He’d call me and say, ‘We have more torque, we have found more power, this development is bringing an extra 20hp and so forth.’ I admit that I too said, ‘Oh, that’s very good, thank you.’ But maybe it was more important not to have 20 more horsepower but the reliability to finish.”

A particular source of unreliability in the 1982 season was the servo motor controlling the Kugelfischer fuel-injection’s metering cam. Responding to a Renault-developed electronic microprocessor that sensed five engine parameters, it increased lap times by 2sec when it failed. Servomotor failures in the hot, high-vibration Formula 1 engine environment cost Renault two wins and the 1982 world championship. “In 1982 we lost about eight races for the sake of an electric motor that cost 100 francs,” confirmed Migeot. “That was because the electronics department was one man, doing everything from electric plugs to the sensors on the fuel injection and he couldn’t cope. The next year the pieces for the motor cost 100 times more. It was undervalued in all sorts of respects.”

“By 1980 the car was very competitive for qualifying”

New developments affecting and relating to the Renault’s turbocharging rolled out during the engine’s career. “The first electronic development was made in 1983 with Renix, a Renault subsidiary,” said Dudot. “It was not successful. Magneti Marelli was too much involved with Ferrari. Renault did not want to be involved with the same supplier as a direct competitor. This was an error. Two years later much progress had been made with the Marelli device: turbo lag, temperature control and piston reliability. Both Renix and Marelli-Weber were in Renault’s mix in 1984 when fuel consumption became an issue with new restrictive Formula 1 rules aimed at corralling the turbos.

At the start of the 1983 season the turbo V6 had larger KKK turbos, delivering 650bhp at 10,500rpm when under 2.2 bar plenum pressure in racing and more for qualifying. Intercoolers were now air/air, lighter and judged more efficient than air/water coolers. Jean-Pierre Boudy, who ran the engine research department, started using water injection after developing the system in his personal Renault 18. Water was delivered in proportion to the density of the incoming air. Cooling water was deployed externally as well with sprays on the intercoolers in qualifying, at first on one side and later on both.

A Renault innovation in 1983 introduced at Monaco aimed to restore some of the downforce lost by new rules requiring flat undersides. A full-width diffuser beneath the rear suspension had four piped exhausts, from the turbos and wastegates, playing across its underside to energise the emerging airflow and add their own impulse to the departing air. Although rivals protested that this somehow constituted a prohibited ‘moveable aerodynamic device’, FISA declared this pioneering ‘blown diffuser’ legal. It was soon copied.

Butterflies at the forward-facing air inlets to the turbochargers provided throttle control, upstream from a Renault-developed device, the Dispositive Prerotation Variable or DPV. An invention of Boudy, it created an annular entry to the turbo’s compressor instead of the usual axial entry. Boudy placed a ring of variable-incidence vanes in the annular passage. The DPV’s control of the vanes varied their incidence from closed to open, either to provide a pre-swirl or to close completely so that the impeller would be in a semi-vacuum that would help maintain its speed until boost was again applied.

“The odds were always going to be stacked against them”

In 1984, the first season of a three-year contract, Renault fitted Garrett AiResearch turbochargers. “We needed special constructions,” explained Dudot. “It was difficult to get specialist turbos from KKK. We knew the possibility of development working with Garrett. Garrett was completely involved in the project and developed turbine wheels from special steels and a high-speed compressor wheel machined from solid in a special aluminium.”

Packaging was completely new with the EF4 as well. With turbos now low at the sides of the V6, compressed air was delivered forward to the intercoolers on both sides and then upwards to the induction plenums. Complete with starter, clutch and turbos, the 1984 EF4 V6 was a 155kg package capable of producing 660-750bhp at 11,000rpm, depending on boost pressure. Its torque peak, reached at 8500rpm, was 354lb ft.

In 1985, the last for works Renault entries until the manufacturer bought the Benetton team in 2000, racing power was 810bhp while for qualifying 1200bhp could be rustled up. Comprehensively revised for the first time to add strength throughout, the 1985 V6 reverted to a longer stroke in search of a broader torque range and better cooling. Feeding inlet ports that now inclined more to the centre, a single plenum chamber replaced separate inlet logs.

The Renix system now fed two fuel injectors per cylinder. It gave a five-position boost choice and a pushbutton for an overtaking spurt – to be used with caution.

Ligier and Lotus used Renault engines from 1984 to 1986 while the original customer and then scoffer, Ken Tyrrell, fitted them in 1985 and ’86. The EF4’s most successful 1984 customer was Lotus, whose drivers put their 95T on the podium six times. The V6 took Elio De Angelis and Lotus-Renault to third in the two world championships that year. Ayrton Senna scored four wins in Lotus-Renaults, his first – of 41 – was from pole in the Portuguese Grand Prix on April 21, 1985.

The Renault F1 effort was a venture into the unknown that could only have been undertaken by a motivated ‘outsider’ to the F1 mainstream. Had Renault not taken the leap into the dark that was the 1½-litre alternative, it is certain that supercharging would have remained unexplored. None of the incumbents had any reason to attempt it. This would have denied turbocharging one of its most productive decades.

Niki Lauda, who had negotiated with Renault for a drive but was rejected as too costly, was critical of the company’s effort: “It can be argued that Renault’s over-zealous commitment to new engine technology may have crossed the demarcation line between day-to-day feasibility and downright wishful thinking. Renault engineers piled one idea on top of another. Taken in isolation each new idea may seem sensible enough. Taken together they tended to add up to an over-technical, excessively complex final product. The interplay of ideas and solutions was such that it became increasingly difficult to sort out certain basic problem areas.”

Motor Sport’s Mark Hughes judged that “this project was fantastically audacious. It brought together a young, inexperienced bunch of people, threw them into a technical programme previously uncharted, with huge pressures and potential rewards and with tools completely untested. There were always going to be fireworks – and the odds were always going to be stacked against them.”

Dudot had the last word. The V6 engine project, he said, “gave us the possibility of this expertise in the company. The five Renault world titles of the 1990s [with Williams and Benetton] were built on the school time of the turbo programme.”

Extracted from Power Unleashed by Karl Ludvigsen (Evro Publishing, £395).