A proposal to reduce consumption and emissions to which current cars owe a lot
At the present time we only talk about electric or electrified models (which, by the way, some policy makers confuse), as a means to reduce emissions. But the battle against consumption and emissions has been going on for a long time. In our history today we have gone almost thirty-five years back, to 1987 in a Reanult Vesta. After these five letters appears the Véhicule Econome de Systemes et Technologies Avancées. The Vesta II, which is our protagonist, was the culmination of Renault’s work on the challenge proposed in 1980, by the French Ministry of Industry, to make a car with an average consumption (90 and 120 km / h on the road, and urban circulation) with a consumption of less than 3 liters at 120 km / h.
Compared to proposals such as the Peugeot Vera or Renault’s own Eve, the Vesta was not a derivative of a series model but a car designed, calculated, developed and manufactured from scratch with the aim of minimum consumption. But yes, there were some principles to respect: it had to offer a habitability equal to that of the Renault 5, similar behavior and performance, and an equal or higher level of safety.
Optimize aerodynamics
The 1987 Vesta II, which centers our story, is actually the ninth (SS9) of the prototypes built for this purpose. Its aerodynamic body was highly developed to the point of having a Cx of 0.186 at a time when the usual figure was 0.30. Currently, most cars move between 0.25 and 0.40, the lower the value being considered more efficient. The objective, always, is to achieve the least resistance of the air to the advance.
The design was a single-body type, with a very sloping windshield (57 degrees). The water drop type body shape was cut at the rear. And the height of the ceiling lowered towards the rear, which in turn narrowed. The bumpers were integrated and the lower part faired. Another important element in aerodynamics, the height of the body, was constant thanks to an air suspension and, as the speed increased, the ground clearance was reduced. The cooling air flow had also been optimized, as it is already known that the air required to feed and cool an engine is always a factor that impairs aerodynamics. In addition, it had a system of movable hatches so that the engine reached the optimum temperature as quickly as possible.
Less than 500 kilos of weight
Weight reduction was another field that had been worked hard. This had been obtained by a careful study of the actual stresses supported by the entire structure. And when we talk about structure, we are not only referring to the bodywork, since the distribution of efforts is made, finally, through all the elements that make up the car, both bodywork and mechanics.
The Vesta had to weigh, in principle, 520 kilos. Of the 508 kilos of the first, the ninth had managed to be 473 kilos. And even this weight loss cure could have been more radical but they did not want to increase the already high price of this prototype. The floor of the car, in composite fiber, was flat ensuring a perfect continuity of the air flow. The windows were very thin and were glued to the body, thus contributing to the rigidity of the whole. The front hood was made of a thin sheet metal, attached to a fiber structure, and the tailgate was made up of the rear window glued in a thermoplastic frame.
And the weight of the mechanical components had also been reduced: the engine of the Vesta II weighed 6.55 kilos less than that of the third prototype (PV3). Altogether, at 473 kilos, the car weighed 25% less than an R5 at the time, which was at 725 kilos. For the engine, a compact and ultralight 716 cc three-cylinder had been chosen. Taking into account the aerodynamics and the tight weight, with this displacement and its 27 HP, it was possible to obtain benefits equivalent to a 1108 cc R5, with 47 HP of power.
All elements of the engine had been optimized to reduce friction. Curiously, for the power supply, they had not opted for an electronic injection system (at that time it penalized urban consumption) but for a very special double-body carburetor, which included a power cut-off system during decelerations. The water pump, which was generally powered by the car’s own engine, in the Vesta II was powered by an electric motor. An electronic system controlled the water pump, or the air intake, among other elements, so that the engine temperature was always at an optimal level. And there was also an electrical management system for the alternator, a notable consumer item in urban circulation.
Consumption
The result was that average consumption of 1.94 liters per 100 kilometers was achieved. In comparative tests carried out by specialized journalists, with the Vesta II real consumption of 2.8 liters per 100 kilometers were obtained compared to the 5.85 liters of a 1108 cc R5 and 5-speed gearbox, which was, at that time , Renault’s lowest fuel consumption model. In other words, the street car consumed twice as much in the same conditions. And it could not be said that this saving was achieved at the cost of penalizing performance: they accelerated practically the same, and the maximum speed of the Vesta II was 138 km / h compared to 143 km / h of the R5.
In this story there is an element that, seen today, in 2021, collides in a remarkable way. We speak of weight, “the enemy” as it is traditionally said among engineers who work in the automotive world. A 1987 R5 weighed, as we have seen, 725 kilos. A Renault Clio E-TECH Hybrid of 140 hp, from 2021, puts the needle on the scale at 1,313 kilos. But we must understand that the demands that a current car has to meet in terms of both active and passive safety, or comfort, among others, are not comparable to those faced by a model seven decades ago. And all the elements that make up these two chapters are kilos that add up. And, we are on the other side of the scale, that current 140 hp Clio, compared to the 47 hp R5, not only offers more comfort and safety, but its approved consumption is 1.4 liters lower.
In any case, this quick trip in a prototype of almost 35 years ago, a Vesta II that anticipated some of the solutions that we enjoy today, serves to better understand the possibilities that engineering offers in terms of advancement, and also the value the prototypes have, as well as the time it takes to actually apply the solutions they provide. One consideration that must be taken into account, especially at a time when political decisions force manufacturers to choose, rather hastily, along paths that are not preferred by engineers, nor are they the best solution.
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