Translation 73-139: an Italian device to improve the "pick-up" of carburettor engines (1973)

In this document

The problem and the principle

The paper, presented at the XXVIIth A.T.I. National Congress (Naples, 27-29 September 1972) and published in the Italian journal A.T.A. (No. 6, June 1973, p. 293), addresses the problem of the "pick-up" of carburettor engines: during a sudden opening of the throttle valve, air flows in faster than petrol, which leans out the mixture and can even cause the engine to slow down p. 47.

Conventional "piston" or "diaphragm" acceleration pumps (fig. 1a and 1b) do not allow for fine atomization of the fuel p. 48.

The proposed device

The authors describe an original atomizer system, inserted between the conventional acceleration pump and the intake manifold. It creates an air-petrol "mixing chamber", fed by a pneumatic cylinder with a piston and spring, charged by the manifold vacuum (0.2 atm), and regulated by an electromagnetic switch controlled by a pressure transducer p. 48-50. The complete operation, numbered from 1 to 10 in figure 2, is detailed step by step p. 50.

Track tests

The device was fitted to an Alfa Romeo 1300 T.I. engine, equipped with a Solex C 32 PAIA twin-barrel carburettor p. 50. Due to a lack of suitable test bench equipment, the tests took place on the track, at the Alfa Sud facilities in Pomigliano d'Arco, on a 500 m measurement base, starting at 2000 rpm in 1st gear, changing gear at 6200 rpm (p. 51, p. 53).

Tables I and II p. 54 give, for two series of tests (two drivers), average times without/with the device of around 24.0 s / 23.2 s:

The authors conclude there is a significant gain, statistically validated at the Institute of Engines Computing Centre p. 51-52, and thank Alfa Romeo-Alfa Sud for access to the track p. 53.

Context

This text is a French translation of an Italian article signed by Mariano Migliaccio and Agostino Scognamiglio, C.N.R. researchers attached to the Naples Institute of Engines. The code "73-139" indicates a documentary translation service, probably used internally at Citroën for technical monitoring.

Historically, the question of the "pick-up" (acceleration) of carburettor engines was a central issue in the early 1970s, a period when electronic injection (notably Bosch K-Jetronic) was beginning to establish itself as an alternative. Alfa Romeo, the manufacturer cited as the test ground, was then renowned for its sporty multi-carburettor engines.

Archivist's perspective

This document illustrates the interest of Paul Magès, and more broadly of the Citroën design office, in solutions competing with or complementary to petrol injection, in a context where manufacturers were seeking to improve performance and fuel consumption while preparing for future anti-pollution standards.

It seems that this translation file is part of comparative monitoring work on carburetion, as suggested by the neighbouring documents devoted to the K-Jetronic Bosch or Zenith-Stromberg carburettors. The care taken in the full translation, including tables, suggests that this text was considered sufficiently relevant for in-depth technical reading within the design office.