Essay : BMC vs Renault: The engine story
They say that great engineering minds think alike, and it’s interersting to see just how the parallel engine development programmes of Renault and BMC>MG developed during the 1950s through to the 1990s.
Robert Leitch leads you through the story of Renault’s engine programmes, and compares them with BMC>MGs to come up with a number of surprising similarities…
Billancourt and Longbridge contrasted
Ventoux, Cléon and A-Series
FOR a one-make website – and was British Leyland ever anything more than a coalition? – austin-rover.co.uk has always tended strongly towards the omnivorous, with plenty of informed enthusiasm expressed at the merest mention of the domestic and European competition. After all, half of the fun of enthusing about any given subject matter is appreciating what the opposition was concurrently up to.
This holds particularly true for Renault’s products, and no wonder – for much of the post-war period the companies seemed to mirror each other in the timing of their product planning, if not the design solutions adopted. Both were front wheel drive pioneers throughout the 1960s, although neither manufacturer’s system was adopted as the tediously uniform and far from perfect industry standard when the rest of the world caught up from 1980 onwards.
It should of course be noted that in corporate structure the two companies were very different; Renault was a large homogeneous enterprise, opportunistically taken into state ownership in 1945, and, until relatively recently, was effectively run as a branch of the French civil service. BMC/British Leyland/Rover was composed of an assortment of formerly competing manufacturers brought together, often reluctantly, in a series of major mergers from 1952 to 1968. Leyland’s transfer to state ownership in 1975 was engendered by a very different kind of political expediency.
The parallels in the product timelines are there for all to see:
· 1948 Morris Minor/1951 Austin A30 Seven – 1946 Renault 4CV
· 1958 Austin A40 Farina – 1956 Renault Dauphine
· 1959 BMC Mini – 1961 Renault R4
· 1962 BMC 1100 – 1962 Renault R8
· 1964 BMC 1800 – 1965 Renault 16
· 1971 Morris Marina – 1969 Renault 12
· 1973 Austin Allegro – 1976 Renault 14
There are quite a few more which could be added – and some gaps as well, such as Leyland taking more than eight years to answer the challenge of the extraordinarily successful 1972 Renault 5.
All of this is intended to set the background for some observations on the small Renault engines and their rival from the opposite side of the Channel, the BMC A-Series.
A new motive power…
In 1946 introduced the 4CV, a Beetle-like four-door saloon, with a rear mounted 760cc water cooled in line four-cylinder engine. Austin’s A-Series was still five years in the future and differed markedly in construction. The Longbridge engine had a one piece block casting and an iron block and head, the Renault had detachable wet liners and an alloy cylinder head. Both engines had siamesed inlet and outlet ports, as much an economy measure to keep costs as close as possible to the dreaded side-valve alternative, as an ingenious means of maximising breathing space within a very small head casting.
The 760cc Renault ‘662’ engine had bore and stroke dimensions of 54.5mm x 80mm, the 803cc Austin engine’s dimensions were 58mm x 76.2mm. The 662’s power output was a not particularly impressive 17bhp, but account has to be taken of poor petrol quality and the precedence of reliability over outright performance. By 1950 the Grand Luxe Versions of the 4CV were delivering a healthier 21bhp, and throughout the decade it was the favoured engine of France’s tuners and sports car specialists.
Foremost among these were Jean Rédelé’s Alpine company in Dieppe, and after 1956, Amedée Gordini, recruited by Renault from Simca as soon as their smaller rival dispensed with the services of the Italian ‘Sorcier’ in an act of unenlightened management which would have done credit to Donald Stokes. From 1952 to 1956 Renault produced its own in-house performance 4CV, the 42bhp R1052, anticipating the Mini Cooper by nine years.
The 1052 figure relates to Renault’s project numbering system, not the engine’s capacity, which was the standard 747cc. The engine’s construction made stretching capacity something of a challenge although Alpine built 662/Ventoux variants of up to 998cc. The illustration of a twin cam head produced by Roger Boudot of Montrouge shows the extent to which tuners were prepared to go to increase the little engine’s power within the limits of its capacity.
In 1956 the engine found a new home in the Dauphine, and a new name – Ventoux, after the Provencal mountain, a celebrated car and bicycle hillclimb course. A 3.5mm increase in bore diameter brought capacity to 845cc and power output to 29-32bhp.
The following year, Amedée Gordini, lent his name and tuning skills to the first sporting Dauphine, producing all of 36bhp from its standard capacity engine.
The sporting Dauphine pinnacle was the ‘1093’ factory homologation special of which 721 were built from 1963-1965.
With a heavily reworked six port cylinder head, the 1093’s 845cc engine produced 49bhp, with aftermarket tuning kits available to produce 70bhp from a 998cc engine fed by a Weber 40DCOE carburettor.
The Ventoux’s career was distinguished not so much in competition and feats of extreme engineering as in the variety of ordinary cars in which it provided faithful service, often in the most extreme of road and climate conditions. It became the defining engine of the 1961 R4, of which over eight million were produced over a 32 year production life, the vast majority Ventoux-powered.
The future arrives – in a van
In May 1959 Renault offered its first front wheel drive product, the forward control Estafette van, with a longitudinal Ventoux engine slung forward of the front wheels. Early in 1962 production of a larger-engined version began. The 1108cc unit was completely new, codenamed Sierra, although in many respects it followed the Ventoux formula with detachable wet liners in an iron block and an alloy cylinder head with pushrod operated valves, now slightly inclined from the vertical to create a wedge-shaped combustion chamber.
The major departure was the adoption of five main bearings for the crankshaft, far from common practice for sub-1300cc engines at the time, and an indication its manufacturer’s ambitions for future increases in power and capacity. Near square 70mm x 72mm bore x stroke dimensions also hinted at the engine’s built-in expansion capacity.
A modest beginning, then a new star is born
Also in 1962, Renault introduced the rear-engined R8, a car history would judge as an engineering blind alley when compared with its BMC contemporary, the ADO16 Morris 1100. The rear-engined Renault had its own technical innovations, such as four wheel disc brakes, but the real advance could easily have gone un-noticed. In order to fall within the French 5CV tax bracket, the earliest models had a 956cc 65mm bore version of the Sierra engine, only 111cc larger than the Dauphine’s Ventoux unit and providing 44bhp.
Larger, more powerful engines and new applications were soon to follow. In 1964 the 1108cc R8 Major offered 50bhp. More excitingly, in the same year Amedée Gordini was given a proper chance to work his sorcery.
The 90bhp 1108cc R8 which carried his name became as much of a national motoring icon in France as the Mini Cooper was in the UK. In 1967 he excelled himself with the 100bhp 1255cc development of the engine. 1970 saw the introduction of the series production 1289cc version of the Sierra engine, with a new eight-port cylinder head.
Bored and stroked to 73mm x 77mm and with an output of 54bhp it powered the new front wheel drive 12 saloon and was also offered detuned to 48bhp in the final versions of the Renault 10, an unloved derivative of the 8 with an elongated nose and tail.
Hitting the supermini bullseye – The Renault 5
In February 1972 Renault introduced the 5, a hugely successful three door supermini with Sierra and Ventoux engine options, which was to remain in production and in strong demand for the next thirteen years. The larger engine in particular served the car astonishingly well – its wide range of capacities allowed Renault an effective arsenal in the hot-hatch wars, while the high-torque, high-gearing philosophy, first demonstrated in the 1289cc 5GTL, caused the industry to reconsider its ideas on the relationship of engine capacity to fuel efficiency.
The Dutch-built Volvo 340 was introduced in 1976 with a larger capacity 1397cc Sierra engine, the extra capacity achieved through a 3mm increase in bore diameter. In the same year this engine variant was offered in locally assembled Australian Renault 12s, but the big technological and sporting excitement came with the 5 Alpine. This car featured the big capacity block with a completely new and exclusive Alpine-built cylinder head.
The engine’s valves were opposed and served a crossflow hemi-head arrangement, although pushrod operation was retained. This development represented the most radical variation from the original Sierra design, and was never emulated in large-scale production versions, which retained the in-line valve configuration until production ended.
Worthy of mention as a Cléon pinnacle, the Group 4 homologation special mid-engined 5 Turbo of 1980 produced 160bhp from a heavily modified Cléon unit, fuel-injected but still with eight pushrod-operated valves. Such was its success that after the required 400 were sold, production was continued until 1984 with a Turbo 2 version which achieved the same output but with greater use of standard internal components. In racing form the Maxi version produced up to 350bhp using essentially the same engine as the first-run 5 turbo.
As an aside, the Sierra nomenclature appears to have been applied until around 1981, after which Cléon was used. The name derives from the town near Rouen in which it was first produced – a possible secondary association with the eponymous pre-Christian Athenian leader seems unlikely, given that individual’s historical notoriety.
1974-78 – Everything Changes
The 12 and the 1972 5 were probably the defining applications of the Sierra engine, and could have been among the last had it not been for the seismic upheavals which shook France’s automotive industry in the 1970s.
In 1966 Renault and Peugeot had entered into an agreement to produce a range of common components. In 1969 they set up the Compagnie Française de Mécanique to design, and build in a plant in Douvrin in northern France, a range of advanced aluminium engines which would meet the majority of the two companies’ future needs. In the mid to late 1960s this seemed a far-sighted commercial collaboration which would bolster Renault and Peugeot’s commercial and technical competitiveness.
What was to happen over the following decade could scarcely have been anticipated. In 1974 Peugeot took over Citroën, four years later they were to acquire Chrysler Corporation’s European car manufacturing operations.
Between these two events, Renault began production of the 14, a five-door hatchback seen as its response to the Volkswagen Golf, and powered exclusively by the suitcase XA powertrain from Douvrin in 1218cc and 1360 cc sizes. It was Renault’s first transverse-engined car, and it was widely expected that the replacement for the 5 would use the same major components.
In planning their new small-car strategy, Renault had not anticipated that in the space of less than a decade, Peugeot, hitherto regarded as a respected compatriot, would become its deadliest commercial rival. It seems probable that Renault abandoned further use of the smallest Douvrin engine when they recognised that they could not have full control of supplies of the most important components of their largest-selling products. Co-operation on the larger Douvrin engines, where economies of scale were far more persuasive, has continued between Renault and PSA to this day.
A new role in a new generation
Renault found itself reconsidering product and investment plans to develop a new, autonomous small car range making best use of their in-house components or, where necessary, developing new ones. There was neither the time nor money to develop a new small engine for the 14 and 5 replacements now required urgently, and when the Renault 9 was introduced in September 1981, the Cléon engine was one of the few recognisable components in the first of Renault’s new generation.
Although installed transversely with an end-on gearbox, in accordance with the new orthodoxy, the Cléon was little changed in principle. A redesigned cylinder head retained the pushrod operation and in-line inclined valves, but advances in casting techniques allowed better breathing and improved cooling. Camshaft overlap was reduced, and a high 9.25:1 compression ratio was adopted for both 1108cc and 1397cc versions, although only the larger capacity versions featured electronic ignition.
Although it received Car of the Year awards in Europe and the United States, the 9 was more remarkable for the efficiency of its production engineering than for advancing or inspiring automotive design. The 3 and 5 door 11 derivative appeared 18 months later, finally laying the ill-starred 14 to rest and, with its bubble-windowed tailgate, adding a little originality and panache to a rather lacklustre product.
As far as the Cléon was concerned the major news was the introduction of a 105bhp 1.4 litre turbocharged variant – Renault were by now at the leading edge of forced-induction engine technology, and hot hatchbacks were the big automotive news of the day. A 110bhp turbocharged version of the longitudinal-engined 5 Alpine (Gordini in the UK) had appeared in September 1981, and the installation in the 11 (and a small number of 9 saloons) built on this work.
In 1985 the most fondly remembered of the new generation trio arrived, the Marcello Gandini-styled Supercinq, finally replacing the longitudinal-engined 5 after a remarkable 13 year production run. The Italian master’s bodywork was a neat and faithful hommage to Michel Boué’s hugely influential original, but underneath the engine and chassis components were near unaltered 9/11.
The Cléon’s final act of heroism above and beyond the call of duty was as motive force in the 5GT Turbo. Still retaining its pushrod valve actuation and carburettor, this big-selling variant is revered to this day for consistently bettering its fuel-injected and multi-valved opposition on paper and for on-road excitement.
Starting in 1985 with a 10bhp advantage over the original 11 Turbo installation, the 1987 Phase 2 version gave 120bhp, trumping its Peugeot arch-rival by a useful 5bhp. Reliability was maintained by rigorous attention to cooling, both of the intake charge and the turbocharger installation itself.
Cléon and Ventoux – the final acts
Well into the 1990s, the Cléon engine continued to play an important role in Renaults increasingly diverse product strategy.
In 1991 the 19 replaced the 9/11 duo, featuring from its launch the 1.4 litre Energy engine which would finally replace the Cléon engine, at least in western Europe. For most of this dreary car’s production life, the Cléon, in 1.2 and 1.4 litre mono-point fuel-injected form, continued as the power unit for the cheapest versions in the range.
Although it was very much a bit-part player in the 19, the Cléon performed a persuasive one-man show in the first three years of the life of a far more appealing Renault, the Monospace Twingo. The success of this inexpensive and versatile car, which easily achieved its 1250 per day sales target, ensured that the Cléon engine was produced in large numbers until the end of production on western Europe.
The final versions, built from 1991 to 1996 came from the plant in Cacia, Portugal and featured Marelli single point fuel injection and a catalytic converter, and capacities of 1239cc and 1397cc. Also used in the earliest Clio, the smaller capacity versions were finally phased out in 1996 in favour of the new D-Type engine, an all-new 60bhp 1150cc OHC unit.
A historical curiosity is the late-production Argentinean and Colombian version of the Cléon engine used in the locally produced 9, 19 and 21. This had a capacity of 1565cc and the same 77mm bore and 84mm stroke as the alloy-blocked pushrod A-Type engine first used in the Renault 16.
The Ventoux engine remained in continuous production for over forty years until 1987. Unsurprisingly, the cause of death was recorded as inability to meet impending emissions regulations. Its place in the Renault 4 was taken by a second revival of the 956cc Cléon engine, which along with the 1108cc high-torque variant powered the car until production ended in 1994
Ventoux, Cléon and A-Series compared:
good luck or judgement
A consistent theme of French foreign policy from the time of Louis XIII and Cardinal Richelieu and, in part, before was the state’s expansion to Les limites naturelles, the Rhine, the Alps and the Pyrenees. In marked contrast to the wars fought and treaties sought in pursuit of these geographical frontiers, Renault’s engineers capitulated easily to the difficulty of stretching the physical limits of the tiny and ancient Ventoux engine. Choosing to leave it as it was, they embarked, lessons learned, on a new campaign which would produce the engine we know as the Sierra or Cléon.
Meanwhile, in the most landlocked city of France’s island neighbour, a group of engineers set their territorial ambitions on every scrap of otiose cast iron in the similarly tiny A-Series engine to reach a frontier hitherto thought unapproachable, an engine close to 1.3 litres in capacity which was reliable, tractable, and above all capable of being built in large quantities using mostly existing machinery.
The goal was achieved in small production runs in the 1275cc Cooper S engine of 1964, then in large volume production form by late 1967 in the Mk.II ADO16 1300.
Their achievement came, literally at a price in the expensive materials and production techniques required to overcome high top-end temperatures and the conflict for bottom end space between bearings and crankshaft webs. The Nimonic alloy used for the A-Series’ exhaust valves was developed for aircraft engine turbine blades; the same valves sat into seats faced with Stellite, a cobalt based alloy. Nitriding and fillet rolling were considered necessary to produce a crankshaft with sufficient structural strength and wear resistance for normal use.
The unseen sophistication of the BMC engine contrasts with the juxtaposition of advanced and unadventurous design in the Renault engines. This characteristic is typical of the idiosyncratic charm of French automotive engineering, examples of which are evident in the work of all four main post-war volume producers. Sometimes the technology used is sophisticated beyond what was previously considered appropriate or feasible for automotive applications, for example Citroen’s hydropneumatic suspension, or Renault’s more advanced turbocharging applications. At other times it appears unabashedly rudimentary and simplistic, but invariably effective – a favourite example being the small-front-wheel drive Renault’s push-pull gearchange.
The lesson of Renault’s engine strategy is that BMC’s interests may have been better served by developing a more generously sized engine based on A-Series principles to power the ADO16. The best evidence is the extraordinarily long stroke 1098cc engine – the 1275cc unit had a shorter stroke and 9.3 per cent larger bore diameter. A new engine to fit between the A and the heavy and physically bulky B-Series may have set the ADO16’s launch back a couple of years, but it would still have been two years ahead of the Simca 1100, Peugeot 204 and Autobianchi Primula, and more able to be expanded to a natural limit of around 1600cc.
It took until 1965 and the ADO14 project for BMC to recognise the need for such an engine, and the design of the E-Series, close in size to the larger Cléon variants once account is taken of its archaically long stroke, is a textbook example of why the engine should not be designed to fit the car.
Originally conceived as a 1200-1500cc unit at a time when the was no certainty that a 1275cc A-series was a viable large-scale production option, the E-Series grew with the Maxi through its development phase, arrived in production form at its natural capacity limits with the same problems of top and bottom end space restrictions as its smaller and much older stablemate. It is a huge credit to the designers of the S-Series, that many years later, they managed to turn the sow’s ear of an engine which powered the early Maxi into a useful suede purse, if not a silken one.
The E-Series, had it appeared earlier, been less technologically ambitious, and been fitted to the right cars, could have been a formidable building-block for BMCs success in the 1960s, rather than a lingering symbol of stagnation and incompetent management at the end of that decade.
Renault and BMC – A broader lesson
After the coups d’éclat of the Mini and ADO16 in 1959 and 1962, BMC manifestly failed to produce the follow-up cars which would complement and eventually replace them. The corrosive effect of near non-existent product planning, quality and production problems and diminishing profitability was masked until the Leyland era by strong loyalty to the old trademarks, and burgeoning demand for private transport.
At the same time Renault, starting from far more modest beginnings, consistently introduced products which could be sold and built in huge numbers – it was part of their philosophy from the R4 onwards not to bother with any market sector which could not accommodate a Renault product able to sell at least 1000 per day, an objective consistently achieved, even with the upmarket 20/30.
The component production infrastructure Renault set up in the 1950s, ’60s and ’70s was the cornerstone of this strategy, and the three engines, Ventoux, Cléon, and A-Type together served it with distinction. As with BMC, bad times as well as good were to come for Renault, particularly the vainglorious AMC episode, but the global infrastructure the French company founded has underpinned its survival.
Meanwhile, their British competitor, consistently fixated with an unproven notion that niche and upmarket products would deliver profits, appeared to implode and diminish before our very eyes. As we watched Leyland/Rover retreat ever closer into its Midlands epicentre, while its erstwhile competitors strode the global stage with confidence, we should perhaps have recognised sooner than we did the inevitability of its eventual collapse into industrial oblivion.
Is the Editor of the Parkers website and price guide, formerly editor of Classic Car Weekly, and launch editor/creator of Modern Clsssics magazine. Has contributed to various motoring titles including Octane, Practical Classics, Evo, Honest John, CAR magazine, Autocar, Pistonheads, Diesel Car, Practical Performance Car, Performance French Car, Car Mechanics, Jaguar World Monthly, MG Enthusiast, Modern MINI, Practical Classics, Fifth Gear Website, Radio 4, and the the Motoring Independent...
Likes 'conditionally challenged' motors and taking them on unfeasable adventures all across Europe.