In 1986, Henry Toivonen drove F1 driver Jonathan Palmer around the Estoril circuit, posting a lap time “that would have qualified him in the top ten” in F1 qualifying. For reference: pole position that year = 1’16.673 (Ayrton Senna, on a dry track). How is that even possible? Let’s find out!
The Lancia Delta S4 embodied the best of the rallying world. You can say that there was an F1 bolide (or if you like — a sports prototype), covered with a carbon fiber body and equipped with all-wheel drive. The engine of this Lancia was equipped with both turbocharger and mechanical drive supercharger, which allowed it to develop about 500 hp. (although rumors on tests were as high as 1000 hp). This looked more than modest, compared to the power of the motor Renault EF15C (and this is what stood on the Lotus-Renault Ayrton Senna) developing about 1200 hp at 12500 rpm. But in fact, even its creators did not know about its real potential, because the then stands could not work with power exceeding 1500 hp!
In qualifying, the power was such that we could not measure it, as none of our dynostands at Viry-Châtillon were designed to handle such power. © Bernard Dudo
In addition, the F1 car was almost twice as light: without fuel and driver 540 kg, against almost 900 kg of the Lancia. And it should be mentioned that rallycars of that time, compared to F1, had no downforce at all.
Conclusion: it’s impossible.
The veil of mystery over this legend is lifted by former Lancia team manager Ninni Russo:
The tests took place a few weeks before the rally. It was a private test, Henry drove for time — it’s hard to say what his exact time was — but it was in the top ten F1 cars after their test at Estoril two or three weeks ago. © redbull.com.
That is, Toivonen’s time was compared to the time shown in the test. Unfortunately, the story about the Lancia Delta S4 being able to overtake F1 cars on tarmac turned out to be a myth.