Handwritten notes and curves on the power and scavenging of the P1 auxiliary engine (1 April 1964)

In this document

Page 3: power curves of the auxiliary engine

On a sheet with the letterhead "STÉ AME A. CITROËN", a handwritten graph plots the auxiliary engine speed as a function of the RPM (axis graduated "1000, 2, 3, 4, 5 N"): one curve is annotated "6200", another "5800 Scavenging pressure", a third "Full power" p. 3.

Notes specify three means of power reduction p. 3:

1. by leaning out,
2. by reducing the compressor engine speed,
3. below 45 HP (for 100% of total power), closing the scavenging inlet throttle in the cylinders, in order to "avoid [the] backflow [of] burnt gases".

A final line indicates: "The 175 cm3 engine produces 11 to 12 HP" p. 3.

Page 4: record on dated graph paper

A second graph, on graph paper, bears two vertical scales — one in blue graduated from 40 to 110, the other in red graduated from 0 to 29 and noted "mkg" (torque) — for a horizontal RPM axis ranging from 1000 to approximately 5000 p. 4.

Three curves appear there: a red cross-marked curve rising then plateauing towards 105, a thick blue curve rising with an inflection, and a thin blue curve remaining stable around 60-65 p. 4.

Annotations mention "220 SE / 2° 195" near the rising blue curve, as well as values "1500 → 3800" associated with a mention "220" p. 4. A handwritten date in red, "1.4.64", appears at the bottom of the frame p. 4. Other inscriptions, noted as uncertain or illegible by the transcription ("Q in litre at 12g8", "Conrad"…), cannot be exploited here.

Context

The P1 auxiliary engine mentioned in these notes is part of the research conducted at Citroën, under the direction of Paul Magès, on two-stroke engines intended for experimental automotive applications during the 1960s. The acronym "220 SE" likely refers to a project or a test engine of the period, but its precise identification goes beyond what the document allows to establish.

This type of record — power, scavenging, and torque curves drawn by hand on graph paper — was a common practice in design offices before the computerisation of engine testing.

Archivist's perspective

These two sheets dated 1 April 1964 seem to constitute working notes directly linked to the development of the P1 auxiliary engine, probably written before or in parallel with a technical meeting, as suggested by their temporal proximity to the "P1 Operation" meeting minutes of Friday 1 April 1964, dated the same day.

The highly technical and informal nature (calculations and curves drawn freehand, abbreviated annotations) makes it a raw working document rather than a report intended for distribution. It concretely sheds light on the experimental approach of Magès and his team regarding the issue of scavenging and the power of two-stroke engines, a subject also addressed in the "REA meeting regarding the 2-stroke engine" folder of 3 April 1964, which follows two days later.