For rally fans, but also for all those who have barely heard of rallying, the era of the Group B cars of the mid-1980s is perhaps the most exciting page in the history of this motor racing discipline.
We are talking about a lot, perhaps too much, power concentrated in lightweight prototypes vaguely resembling production cars and with technical solutions often pushed to the extreme, which soon showed the disturbing limits of safety.
What not everybody knows is that Group B could have been an even more demanding evolution for the development capabilities of the teams, in the so-called Group S. It was due to debut in 1987, but was blocked, like Group B itself, by the rule change that followed a series of dramatic accidents that convinced the FIA to focus more on safety and promote the less powerful, series-derived Gr. A cars.
Well, among the Group S cars that never came into being was the car that was to take the place of the Lancia Delta S4 in 1987. It was born in 1986 as the ECV and remained there, at the prototype stage.
Among its secrets, in addition to its composite structure, the ECV featured a new and very powerful engine with a special supercharging technology, called Triflux, which allowed a power delivery never seen before.
1986 Lancia ECV prototype
The secrets of the Triflux
The Triflux design was the work of engineer Claudio Lombardi, engine and technical manager of the Lancia team Martini, who in fact anticipated the sequential turbocharging prototype, developed more than 20 years later for the most powerful turbodiesel engines.
The basis was the same unit as in the S4, a 1.8 four-cylinder (1,759 cm3) already equipped with twin turbocharging, i.e. a KKK K-27 turbocharger with 2.5 bar pressure for the mid-high revs and a Volumex R18 volumetric compressor, active from 1,500 rpm, assisted by a twin air intercooler. In the S4 it exceeded 600 bhp.
The engine and intercoolers of the Lancia Delta S4 Stradale
However, Lombardi replaced the volumetric compressor with a second turbocharger: in fact, the belt-driven compressor absorbed more mechanical energy, while the exhaust gas ones did not have this problem. Moreover, Lombardi considered it more efficient to use two smaller turbines rather than simply adopting a larger one, but with more inertia and therefore with delays at the bottom of the rev counter.
As with the modern two-stage turbochargers that came later, the system worked by directing the exhaust flow initially to one turbine, so that it was ready at low revs, and then, from 5,000 rpm onwards, splitting it so that both worked in parallel to achieve maximum power. Hence the name Triflux, indicating precisely the presence of two separate flows for the exhaust gases, plus one for the intake air.
That was not all. In order to fit the two turbos, the four-valve-per-cylinder, cylinder head was redesigned according to a cross-flow scheme: this meant that both the intake and exhaust valves of the cylinders were not arranged on the same side, but alternately.
This allowed the engine to have a homogeneous temperature, a more even expansion of the materials and allowed for increased compression and turbo pressure, as well as generating favourable turbulence in the combustion chambers.
The 1.8 Triflux engine of the Lancia ECV
The Triflux engine was capable of generating power ranging, depending on the settings, from 600 bhp to around 800 bhp and even a little more, but above all it had a great willingness to deliver that power. So brutal was it that it impressed the very drivers who tested the prototype and who, years later, agreed that a vehicle with such acceleration was extremely dangerous on tracks, circuits or on the road itself.