Paul Magès note: the unfavourable price/quality ratio of the rotary engine (Nov. 1972)

In this document

I. The price

The note opens by stating that "price is the main element of the study" p. 1. Magès recalls that the cost of the birotor had long been compared to that of a 4-cylinder engine, before the comparison shifted, "for some months now", towards a 6-cylinder — and that the costings "for 200 per day" yield a value "well above" that of a 6-cylinder p. 1.

He poses the central question: do the additional qualities provided by the rotary justify this extra cost to the customer, knowing that the competition can offer a cheaper 6-cylinder engine already offering the same qualities p. 1?

He also specifies that the price of an engine includes its entire functional environment: fuel system, tank, radiators, pollution control, exhaust, etc. p. 1. Finally, he announces his method: to compare the rotary to the conventional engine quality by quality, without mentioning the estimated price of the rotary, in order to deduce a posteriori the price it should have to be "honestly competitive" p. 1.

Conclusion

Magès makes a decision: the rotary engine only has a chance of developing if it costs less than a conventional engine "and its endurance is at least as good" p. 2. He judges that the only advantage of the birotor — its balancing — does not justify its price compared to a 4-cylinder, and that a 6-cylinder is even superior on this point p. 2.

He mentions an internal reference to the study ("4-3 and graph 4") showing that the vibration filtration of a 4-cylinder mounted on the "L" reaches a very low level in the passenger compartment, putting the rotary's asset into perspective p. 2.

He lists the disadvantages of the birotor: excessive fuel and oil consumption, air conditioning discomfort in town, vibrations at idle, a question regarding "service life" accompanied by a note (1) specifying that this doubt contradicts claims of reliability, and a depreciation upon resale feared by buyers of second-hand vehicles p. 2.

He concludes that the future promises of the rotary in terms of anti-pollution cannot convince the customer to pay more today, and hammers home in capital letters: "THE PRICE/QUALITY RATIO MUST BE AN ABSOLUTE RULE FOR A DESIGN OFFICE" p. 2. The note is signed "Paul Magès November 1972" with a handwritten signature p. 2.

Context

The Wankel engine, known as the rotary, was experimented with by Citroën in the 1960s-1970s, notably via the Comotor joint venture with NSU, giving birth to the Citroën GS Birotor marketed briefly in 1973-1974. The project was a commercial failure, partly for the reasons of cost and reliability that this note specifically mentions.

Archivist's perspective

This document is probably one of the rare writings where Paul Magès, known for the hydropneumatic suspension, expresses his opinion on a technological choice that is not his own — and his scepticism is clear: as early as November 1972, he points to a price/quality ratio unfavourable to the rotary p. 1-2, one year before the commercial launch of the GS Birotor.

His engineering method — comparing quality by quality before setting a target price p. 1 — reveals a rigour of analysis that also sheds light on his approach to his own inventions.

The advertisement linked Publicité France Motors / Automobiles Mazda sur le moteur bi-rotor et la pollution, praising the anti-pollution merits of the rotary, offers an interesting counterpoint: it illustrates the commercial argument that Magès judges to be "very light" p. 2.