The fuel allowance had been reduced from 220 to 195 litres, a restriction that paradoxically allowed engineers to fit a smaller fuel cell, reduce the tub height behind the cockpit, and install new engine management electronics – including, for the first time, a dashboard readout showing the driver exactly how many laps of fuel remained.
Renault had withdrawn its works team ahead of 1986 for financial and strategic reasons, though the manufacturer continued to supply engines to Tyrrell, Ligier and Lotus through its Renault Sport operation at Viry-Chatillon.
There, chief engineer Bernard Dudot created the EF15B – an evolution of the previous year’s unit featuring a pneumatic valvetrain that replaced conventional valve springs with compressed air, saving weight and preventing surge, alongside an ignition system where each spark plug was fitted with its own miniature ignition coil.
Lighter, lower and significantly more ambitious than the outgoing engine, the new unit could safely rev to 12,500 rpm and produced a reliable 900 brake-horsepower in race trim.
In qualifying, it was something else entirely.
Senna on his way to victory in the 1986 Spanish GP
Grand Prix Photo
While fuel conservation and reliability concerns limited power to around 900bph during the races, in qualifying there were no such qualms. There was even a special variant of the engine fitted with water injection and no wastegates. Boost was turned to the maximum, special turbochargers were used, and even different gearboxes were fitted to cope with the extra power generated by the 1.5-litre V6.
Senna’s lead engineer, Steve Hallam, later recalled that the team changed the turbochargers after every qualifying run, because the turbos would be so stressed they were finished after a single lap.
It was estimated that the difference between race and qualifying trim amounted to as much as 300bhp. Precise figures remain a matter of speculation, but it is widely accepted that the 98T in qualifying configuration was capable of producing well in excess of 1,000bhp from a 1.5-litre engine.
Senna would finish the 1986 season in fourth position behind Alain Prost, Mansell and Piquet.
The Lotus 98T was the final Formula 1 model to wear the iconic black and gold John Player Special livery, a colour scheme that had defined Lotus since 1972.