Chapoux (UTAC), "Anti-pollution action and fuel economy", Pollution Atmosphérique No. 61, 1974

In this document

An in-depth article on pollution and consumption

This offprint from the journal Pollution Atmosphérique (No. 61, January-March 1974) reproduces a presentation by Édouard Chapoux, A. & M. engineer and technical director of UTAC (Union Technique de l'Automobile, du motocycle et du Cycle). The author poses the question of whether the anti-pollution fight has actually reduced automobile fuel consumption p. 31.

Consumption according to vehicle generations

A study conducted by UTAC at the request of the Ministry for the Protection of Nature and the Environment compares, on the European Cycle, vehicles from before 1968, from 1968-1972, and from after 1972 p. 31-32. Average consumption reportedly decreased by nearly 6/100 between pre-1968 models and those from 1968-72, and by nearly 12/100 compared to models from after 1972 p. 31-32. Homologation results are reportedly on average more than 13/100 lower than those recorded on vehicles in service p. 35.

Notable comparison: American vehicles reportedly consume more than 40/100 more on the European Cycle than European technology p. 34-35, and light commercial vehicles reportedly consume double that of passenger cars of equal power p. 35.

Idle adjustment

Tests on a medium-displacement vehicle show that the idle adjustment (CO content, engine speed) causes consumption to vary by up to 0.4 l/hour between extreme settings, representing a rise of 100/100 p. 37. On the full European Cycle, consumption would vary between 360 and 373 grams for CO contents of 1.1 to 7/100 p. 37.

Speed, load, aerodynamics

Tests at Montlhéry, with nine configurations of load, tyre pressure, and trim (table p. 38), give consumption at stabilised speed ranging from 7.0 l/100 km at 80 km/h to 13.1-15.1 l/100 km at maximum speed p. 39. The vehicle's trim (aerodynamic drag) has a clear influence, as does the engine speed during acceleration p. 39-41.

Starter, battery, electrical accessories

Chapoux calculates that a 3-second starter burst costs the equivalent of 3.5 g of fuel, making stopping the engine worthwhile only beyond 32 seconds of immobilisation p. 43. The use of electrical accessories (heating, windscreen wipers, headlights) would increase consumption by 17/100 (253 g against 290 g measured on the European Cycle) p. 43.

Practical conclusion

The author recommends smooth driving, avoiding unnecessary roof racks, a well-adjusted idle, and measured use of electrical equipment p. 44.

Context

The early 1970s saw the progressive entry into force of automobile anti-pollution standards in Europe and the United States, with the famous "European Cycle" for homologation. UTAC, the official French testing laboratory, then played a central role in vehicle evaluation. At Citroën, these same years were when Paul Magès developed and refined the hydropneumatic suspension, with no direct content link to this article, but in a shared industrial context where French automotive engineers followed closely the regulatory developments affecting engines and consumption.

Archivist's view

This document does not directly concern Magès' work on suspension, but bears witness to the technical and regulatory climate of the French automobile industry in the mid-1970s, a period when he was completing his major achievements at Citroën. Its presence in the collection suggests a personal or professional interest in questions of carburetion and engine efficiency, themes similar to those addressed in the Revue Automobile clippings on the Bosch K-Jetronic injection and the Translation of the 1973 ATZ article on the K-Jetronic kept in the same file.

The numerous handwritten annotations (red lines, circles, reference numbers) suggest that the document was read and annotated with attention, probably to extract numerical data useful for a broader reflection on carburetion and anti-pollution standards p. 31, 35, 37.