Renault 3 - Engines

Engines

Early versions of the Renault R4 used engines and transmissions from the Renault 4CV. The original design brief called for an engine size between 600 cc and 700 cc but there was no consensus as to whether to use a four-cylinder unit or to follow Citroen with a two-cylinder unit. With Volkswagen now rapidly growing their market share across Europe and North America, Renault also gave serious consideration to an air-cooled boxer motor option for the forthcoming R3/R4. Using the existing water-cooled unit from the 4CV was a solution, especially in view of the extended period of teething troubles encountered by the Renault Fregate, which had followed Renault’s last attempt to develop an ambitiously innovative powerplant. The powerplant of the 4CV was larger than that specified by management for the new model, but Renault addressed this by reducing the bore so that the overall capacity of the power plant destined for the new R3 came in at 603 cc, comfortably at the lower end of the required 600–700 cc range. However, since they already had the 747 cc version of the engine on the shelf, well proven in the 4CV, it made sense to use this as well in what would in many respects be the older car’s successor. Therefore in 1961 the R3 emerged with cylinder bore and stroke set at 49 mm × 80 mm while the R4 was launched with the 54.5 mm × 80 mm cylinder dimensions from the existing engine, giving rise to the 603 cc and 747 cc engine sizes with which the cars were launched.

Moving the engine from the back of the 4CV to the front of the new model nevertheless involved significant planning: design changes to the unit were introduced as part of the process. The inlet manifold was now a steel casting whereas on the 4CV it had been constructed of a light-weight alloy: this was driven by cost considerations now that aluminium was not so inexpensive as it had been fifteen years earlier. Renault also took the opportunity to introduce a feature which subsequently became mainstream but which at this stage was not on the agenda of competitor manufacturers (other than Peugeot). For the new car Renault designed a “sealed-for-life” cooling system, supported by a small expansion tank on the extreme right side of the engine bay. The cooling system contained a type and quantity of anti-freeze intended to enable operation without topping up or other intervention throughout a car’s life provided ambient temperatures below minus 40 degrees were avoided.

The engines were larger than the small 425 cc (later 602 cc 29 hp), engines in the 2CV. The R4 always had a four-cylinder watercooled engine. The original Renault R4’s engine capacity of 747 cc served to differentiate the model from the more powerful Renault Dauphine, but the Dauphine’s 845 cc engine was used in the 4 itself from 1963 onwards: for most markets at this stage the Dauphine engine now came as standard in the top of the range Renault R4 Super, and was available in some other versions only as an optional extra. Given that Renault’s 603 cc, 747 cc and 845 cc engines all shared the same cylinder stroke and were all of the same basic design, it is likely that there was very little difference between the manufacturing costs of the basic engine block between the three. From the perspective of the sales and marketing department, they did fall within different taxation classes (respectively 3CV, 4CV and 5CV) but at this end of the market tax level differences were by now less of an issue even in those European countries that still taxed cars according to engine size.

With time, the increasing trend to production of Renault 4s in a wide range of countries reduces the validity of generalised statements as to which engines were fitted when: in French built cars the old 845 cc engine soldiered on in the more lowly versions until the mid-1980s, but in 1978 the top end Renault 4 GTLs received the new 1108 cc engine: this engine was no longer new to Renault, however, being the five-bearing “Sierra” engine, first installed in the Estafette van and R8 in the summer of 1962. A smaller version (956 cc) of this new engine replaced the by now venerable 845 cc engine in the 4 in 1986. Unlike the original "Billancourt" engine from the 4CV, Renault's “Sierra” engine rotated in a clockwise direction, so fitting it required reversing the direction of the differential in the gear box in order to avoid producing a car with one forward speed and four reverse speeds.