The Renault 18 Turbo
A Splendid Family Car, with Racing Connotations
The Renault Group, France’s biggest car manufacturer, having decided to use turbo charging for winning at Le Mans and then for initially-successful participation in F1 racing, have justified this technical innovation by applying this form of supercharging to the exciting mid-engined Renault 5 Turbine and the commercially-available Renault 18 Turbo (£6,589). The latter is an excellent all-round family car, to which turbocharging has been sensibly applied, to increase performance very materially while not clobbering petrol economy and at the same time retaining the desirable facets of a medium-sized family saloon.
Turbocharging, with its origins long ago in the realm of high-altitude aeroplanes and Indianapolis racing cars, was innovative when Renault came up with it for modern F1 racing, but is now becoming commonplace for high-performance road-cars, with Audi, BMW, Lotus, Peugeot Diesel, Porsche, Renault, Saab and Volkswagen offering it as an aid to better performance. Renault have been circumspect in using it for the 18. The Garrett TO3 installation blows cooled air into the single-barrel 32DIS Solex carburetter, as Mercedes-Benz used to blow air into the carburetter of their supercharged models, from the 16/60 h.p. to the great 38/250 h.p. sports cars. (This recalls the impertinent letters of a young man I wrote to the old Light Car & Cyclecar magazine, about whether this was the better way of boosting an engine, which at least earned me exciting demonstration rides in supercharged 36/220 Mercedes-Benz (blow-into) and 2-litre Lagonda (suck-from), when I was still wearing a school-cap . . .).
I see that Renault claim that by placing the carburetter downstream of the turbocharger the engine can take in cooled air and that fuel condensation is avoided — just the argument in favour of the little-used blowing-through the carburetter system when I wrote to the motoring Press on the subject some fifty or more years ago . . . The air-cooler behind the Renault 18’s water radiator reduces air-intake temperature to around 50 to 60 deg. The feed is through Tecalamit “flexibles”, which stand up to the maximum boost of approx. 11.7lb./sq. in. Above a boost pressure of about 8 1/2 lb./sq. in., the exhaust feed to the turbine is by-passed. The engine’s compression-ratio has been reduced from 9.3 to 1 to 8.6 to 1 to align with the supercharge, and the boost pressure is prevented from exceeding the aforesaid maximum by an ignition cut-out. A further turbocharging refinement is that, in conjunction with the transistorised-ignition, a quartz “accelerometer” acts as a “pinking” sensor, temporarily retarding the ignition. Renault claim that good economy is wooed by this device, as it enables a quite high c.r. to be used in conjunction with the boost from the turbocharger.
Nor is that all, because the Renault 18 Turbo has stronger reciprocating and crankshaft assemblies than those of the normal 18, the lubrication system has been carefully revised, and valves and pistons are made of more-highly-heat-resistant materials. The cooling system has also been revised. So this is not just a case of tacking on a turbocharger as an inexpensive means of increasing the power output of a production engine. As for the Renault’s turbocharger itself, it is said to have a meticulously balanced impeller assembly, lubrication of its bearings is generous, and it is constructed of special materials in respect of turbine and housing. To obtain the desired low noise-level, not only has the Renault 18 Turbo’s body been sound-proofed, but the engine employs valve timing — 10-50-50-10 — suited to the exhaust flow and temperature characteristics of a boosted power unit, which Renault claim eliminates the vibration which backfiring on the over-run can cause.
Having applied themselves to turbocharging this all-aluminium non-transversely-mounted 1 1/2-litre engine, after much experience gained from developing the F1 racing turbo engines of that capacity, Renault did similar work on the 18 as a whole, to meet the performance increase. For instance, the front suspension, by four unequal-length wishbones and coil springs, with telescopic hydraulic shock-absorbers, is of new design, with negative-offset, as used for the Fuego, 20 Diesel, and now the 18 Diesel and 18 Turbo Renaults. It has a spring-rate of 170 lb./in., an increase of 43 lb./in., a periodicity of 0.84 with the car empty, increasing to 0.89 at full-load, the camber-angle varying from plus or minus 30′, the castor-angle being 3˚ 20′ and the king-pin inclination 13˚ 20′. The anti-roll torsion bar is 19 mm. in diameter.
Likewise, the rear suspension, independent on this front-wheel-drive car, has been stiffened, the spring rate for the coil springs going up by 28 lb./in., and the periodicity is 0.66 when the car is empty, 0.86 at full load, camber 0′ to minus 30′, while toe-in is 0-0.36″, against 0.04-0.11″ of the front wheels, whose off-set scrub radius is – 0.2” at the point of contact. The rear anti-roll torsion bar has a diameter of 25 mm. The servo braking of the 18 Turbo has been uprated in similar fashion. Thus the Master-Vac is an inch larger in diameter, at 9″, the 2.12″-dia. front-brake pistons are 0.23″ bigger, and the front ventilated discs are 0.40″ bigger, at 9.37″, while the rear brake drums of this diagonally-split dual-circuit system have gained an increase in diameter of 1.89″, being 8.98″ in diameter.
It will, therefore, be appreciated that this Renault 18 Turbo is a specialised car and not just a casual adaptation of the ordinary 18, which, by the way, is the Renault Group’s best-seller in the UK. For the performance it offers the family motorist, this five-speed, fully-equipped Renault represents excellent value-for-money, in spite of being the first volume-production turbocharged car from a French factory. On the road the first impression is of very light steering, very usable acceleration, and an engine that is almost inaudible when idling at 750 r.p.m., and which is decently quiet at normal cruising speeds. only making its presence heard with a power roar at around 5,000 r.p.m. As for turbo-lag, it is not apparent as a pause before picking-up, more a matter of waiting for the power to flow, which it does from 2,000 to 2,500 r.p.m. onwards. Wind noise is very low indeed and as the engine will not often be held at speeds as high as 5,000 r.p.m in this country, because that means exceeding 104 m.p.h. in fifth gear, the general sound-level is very satisfactory. Admittedly, the Renault Turbo will not live with the similar engine-size VW Golf GTi with the Schrick-KKK turbo installation but this car costs nearly twice as much as the Renault 18 Turbo and also it is a case of comparing a super-sports saloon with a GT family saloon.
My first experience of this interesting Renault was a long run over Motorway and country roads. It made a suprisingly fast time and was enjoyable to drive. I was surprised at the way in which the fifth gear could be used almost continually, without feeling that the engine was being stifled, and by the splendid surge of power as the boost came in with an almost imperceptible whine, which vanished on the over-run, confidence inspired by the powerful brakes, which possess a sort of wrap-round feel rather than over-servo-ing. The suspension is firmer than I had expected, after experience of other Renaults, giving notice of bad going and promoting a lateral motion to the body under these conditions, without this stiffness constituting an uncomfortable ride. Nevertheless, fast cornering, especially round acute bends, causes roll, but this never got out of hand, the back-end suddenly coming into line with a sharp thrust to the upright stance.
Some testers have found the power-steering too light. It is certainly “finger-and-thumb” effortless at speed and very useful for parking, but I did not dislike this and it is said to be a palliative for excessive under-steer. Only when cornering at the limit, which is not perhaps the intended everyday role of this Renault Turbo, does such light steering have the disadvantage of very little feel at the front wheels. It is geared just over 2 1/2 turns, lock-to-lock (3 1/2 with manual steering), and there is faint servo-sound towards full lock, on which you are told not to park.
The driving position is commandingly high and although at first I thought the velour-cloth, petal-type high-back seat hard and too clingy, adjustment of the squab angle with the big knob provided for the purpose gave more comfortable seating. The steering column is also adjustable. In fact, this Renault Turbo is very complete in its amenities. Thus there is electro-magnetic central door-locking, with tiny, very neat, cill indicators (although it does not include the boot, which has its own key-lock), easy remote-control of the driver’s door-mirror, electrically-operated windows in the two front doors, and a laminated windscreen, etc. If you want to spend more, a sun-roof costs £206.31 extra, Super Gloss metallic paint £51.58, and you can even have leather upholstery for another £577.07.
On the road this Renault 18 Turbo is “different”, an interesting car to drive. The 1,565 c.c. (77 x 84 mm.) 5-bearing, alloy engine with valves inclined in the classic “Peugeot” manner but operated by push-rods and rockers, produces 110(DIN) b.h.p. at 5,000 r.p.m., thanks to the turbo-induced boost, and 133.8 lb./ft. torque at a modest 2,250 r.p.m., also by DIN rating. Thus speed and acceleration from this 8-ft. wheelbase, 19.7-cwt. saloon are in the 2-litre, or even 2 1/2-litre. category. Top pace is 113 m.p.h., 0-60 m.p.h through the gears takes 10 1/2 seconds, 0-80 m.p.h. a matter of 13.6 seconds, and it is possible to increase speed from 40 m.p.h. in an urban area to the legal 60 m.p.h. open-road British cruising speed in 8.4 seconds, without dropping out of fifth gear. In this ratio the engine runs smoothly, although a four-cylinder unit, doing 3,250 r.p.m. at an indicated 70 m.p.h., whereas running in 4th at this speed means an increase of 750 r.p.m. The gearbox has a dog-leg gate, reverse left and back, fifth gear right and forward, of the “H”. No gear baulks from rest but on the move the change is somewhat notchy. Neither a poor nor an outstanding gearbox; the lever has a substantial knob and fairly long movements. The central handbrake lies out of the way but on the test-car was fiddly to release completely and if it moved about an eighth of an inch to the right its warning light came on.
The instrument binnacle is as on the Renault Fuego, and quite well arranged. Main dials are the 140 m.p.h. Jaeger speedometer with k.p.h. readings and six-figure total (and trip) mileage recorders, and the tachometer, which is red lined from 6,000 r.p.m., with a prior warning from 5,500 r.p.m., in addition to an economy segment, marked solid from 1,300 to 2,500 r.p m., straked to 3,000 r.p.m. A combined heat-and-fuel gauge is between these and there is an oil-level gauge below this giving the sump-level reading with the engine stationary and the ignition “on”: this in lieu of an oil-pressure gauge. There is also a small boost gauge, calibrated in coloured strips instead of figures. It is intended to be a further guide to economy-operation, its white zone representing normal boost of 100 to 1,000 m-bars, the orange zone 1,000 to 1,500 and the red more than 1,500 m-bars. Frankly, I preferred to concentrate on driving this energetic Renault but even so I got 25.7 m.p.g. (4-star) on a rather quick dash from Acton to Wales. With more restraint no doubt 30 or more m.p.g. would be achieved. The fuel filler cap is under a flap on the off-side, but a lock is extra. The tank holds 11.66 gallons (53 litres). Reverting to the fascia, there are 13 warning lights in a row across the top of the instrument panel, which has rheostat control of illumination intensity. Very big press-knobs look after hazard-warning and rear fog lamps on the left, rear-window demisting on the right. The door locking is controlled by a smaller switch on the panel itself. All the instruments are under an anti-dazzle panel and are easy to read through the two-spoke 15″ steering wheel, which has a thick leather-trimmed, but not uncomfortable, rim. The steering pulls if the throttle is opened quickly in the lower gears but the effect is not so pronounced as on the 30TX with 32 more b.h.p. There is nice castor-return action from the rack and pinion mechanism but I would not call this notably precise steering.
The central console contains the switches for the rather-leisurely electric windows, where they are more accessible than many set lower down, the aforesaid boost-gauge and a Kienzel quartz clock, being between the pushes. Below is the Philips stereo radio (an extra, as is the n/s door mirror), using a roof aerial, then the simple-to-understand heater/ventilation controls with the variable-speed fan operated by a vertical knurled knob, the system functioning well, with visible flaps in the fascia vents, although these only adjust horizontally. Finally, going down the console, there is a useful coins-container, a lighter and a drawer-type ash-tray. The combined console and transmission tunnel is wide but the pedals are not much off-set to the left, although a normal-size foot will park only beneath the clutch pedal. Stowages include door-bins and an unlockable drop cubby.
Three stalks operate the remaining services. On the right the longer one works the lamps and, conveniently, the French-note horn, the short upper one the turn-indicators, the left-hand stalk looking after wipers and washer, with multi-purpose settings. There is full width floor carpeting, guttering above the doors which did not prevent tiny drops of water sometimes reaching the seats, soft head-restraints to the front-seat squabs and very well-contrived door arm-rests-cum-pulls. The doors have useful strip-type “keeps”. I was surprised to find, instead of the expected Michelin tyres, that the test-car was shod with Goodyear NCT HR65 185/65 HR14 steel-belt tyres, but I have no complaints on that score! The four-stud light-alloy wheels are an ugly aspect of this rather nice and unusual-looking Renault. On this subject, I could do without the “Turbo” name, and speed-lining along the car’s body sides, for this is no rorty boy’s racer; the neat Turbo insignia on frontal grille and boot should surely suffice? Especially as the front air-dam and rear spoiler are not too obvious, particularly to family-car folk.
The boot is a box taking a commendable amount of luggage (13 cub. ft.) but it is the opposite of a Hatchback, for the high cill means humping loads up into it. The unobstructed boot floor has a detachable rubberised mat. The test-car was blue-hued, correctly for a French car, in my opinion, but the interior is plasticky and some of the welding rather obvious. The headlamps are by Cibie.
The rear-hinged bonnet has a driver’s-side release lever. Its prop. was difficult to withdraw and was already corroding. The turbocharger is quite small, on the near-side of the engine. The Renault battery, on the off-side behind the radiator, is rather low-set but has the traditional master-switch incorporated in one of its terminals and sparking plugs, ignition distributor and oil-filler aec fully accessible. The doors close nicely, the clutch is commendably light and smooth, the engine easy to start, using the manual choke convenient to one’s right hand, and no oil was wanted after 500 miles.
This Renault 18 Turbo is a significant car and on the rear window of the test-car there was a sticker proudly reminding us that the Company’s other turbocharging application, on the Renault 5, won this year’s Monte Carlo Rally. The 18 Turbo would be a nice car in which to drive to a Grand Prix, especially if Renault can regain their former victorious form with their turbocharged F1 cars! — W.B.