A fuel winner
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RVI's engine in its non charge-cooled G260 produced a very economical fuel consumption, though real pace was lacking. Bryan Jarvis feels that the vehicle will be of greatest interest to operators running below 38 tonnes
RENAULT'S 9.8-litre-engined G260, its first new maximum weight tractive unit since the 1978 Berliet-Saviem merger, may have made a slow entry to the British market but it has certainly made a surprising entry to the fuel economy charts.
Almost 12 months have passed since Seddon Atkinsons' Gardner-powered 401 became the first to breach the magic 40.36 lit/100krn (7mpg) barrier. Bedford since then has improved upon this still further with its Cummins LT10-250 engined TM 3800, taking the record way up to 38.86 lit/1 00km (7.27mpg).
The G260, tested during three freezing December days, has Picture above: When the proposed 80km/h (50mph ) speed limit on dual carriageways for vehicles over 7.5 tonnes is introduced it will place the G260's engine speed at the top of its torque band at 1,500rpm and be 'deal for top gear cruising. slipped neatly between these two top performers with a very creditable 39.57 lit/100km (7.14mpg).
At the heart of this outstanding result is Renault Vehicules Industriel's M1DS 06 20 45 turbocharged engine.
RVI has developed it as a low speed, high torque unit which when operated at 38 tonnes offers a power to weight ratio of 5.05kW/tonne (6.90bhp/ton). As installed in the chassis it is rated at 192kW (258bhp) at 2,200rpm, while its maximum torque of 982Nm 1724 lbft) occurs at 1,24Orpm. According to the manufacturer, the engine will return its best minimum-full-load specific fuel consumption of 204g/kWhr between 1,400 and 1,600rpm, which represents between 45 and 52mph in top gear.
To keep drivers ever-mindful of the engine's abilities Renault recommends that they try to hold engine speeds at between 1,200 and 1,700 rpm and, whenever possible, to as low as 1,100. For motorway cruising, running above 1,700rpm should only be in eighth gear. A colourcoded plastic ring is added to the rev counter to catch the driver's eye and remind him of this.
For much of the motorway running the engine's low-speed high-torque characteristic held well, for at maximum permitted speed this equated to 1,900rpm in top gear.
Normal motorway gradients present few problems while others, such as the long, undu lating climb towards Shap, can play havoc with journey times if the driver becomes too conscious of the coloured flags on the rev counter.
The gradient at Kendal pulled the vehicle down to 48.3km/h (25mph) in sixth gear while the Shap climb slowed it to 30mph, also in sixth.
I tried to maintain the recommended engine speed where possible but had 1 been heading for the Stranraer ferry I would have been tempted to over-ride the coloured marker on more than just top gear.
In top gear, however, over Aroad sections at the legal maximum speed the engine ran at 1,300rpm. On level or gentle rolling terrain such as the Al running down towards Wetherby, driving in overdrive top gear placed little strain on the driveline even though the engine was at the lower end of its torque band.
On other roads such as the A74 into Glasgow or parts of the A68, steeper gradients meant that constant gearchanging into direct ratio and lower became necessary.
Renault uses the same gearbox as on its premium tractive unit, the R310. It is RVI's own B9150, an eight-speed synchromesh range change unit weighing 316kg (6971b) and having twin countershafts. Its deep, low first gear ratio is a crawler gear (not synchromesh) of 11.09:1 while top gear is an overdrive ratio of 0.75:1.
The unit, which is built at RVI's Boutheon plant near St Etienne, is designed to be matched with engines of power ratings from 160 to 300kW (220 to 400bhp) and torque outputs from 1,000 to 1,700Nm (738 to 1,254 lbft).
Driving through the P1141-B single-reduction final-drive rear axle, with its standard 5.125:1 ratio, this gives a maximum geared speed of 114.2kmh (71mph).
As I had previously found when I drove a Continental version in France last year (CM 16 April 1983) the double H-range change was noisy and clunky in operation. Although the clutch was quite light and easy to depress, the gear engagement was on the stiff side, particularly when crossing the gate between fourth and fifth gear and I took a long time to get used to it.
On Mira's test hills the G260 made light work of moving off from rest on a 1 in 4 in crawler gear, despite a wet surface.
I was unable to carry out the normal rolling road brake tests, but because we still include the track tests at Mira, these are the results that are published. Despite a damp track the G260's brakes pulled up straight and true. On the road the service brakes worked progressively and without a hint of instability.
Temperatures overnight at Gretna were minus 4 degrees C, which left the cab covered in ice for our early start.1 half expected starting problems but the engine fired after five or six spins of the starter and within 15 minutes the cab heater had warm air circulating and the windows demisted.
Icy patches at West Woodburn and Kilnpit Hill caused wheel spin but not enough to impede our progress. Luckily the threemile-long descent into Shotley Bridge, with its very uneven surface, was dry enough to allow normal progress. Here the Renault's semi-elliptic leaf springs and anti-roll bars combined well to give a firm, controlled ride with only the minimum of fore and aft pitching.
The G260's Club-derived cab has a well balanced feel to it; it is mounted at the rear on two rubber-suspension units with a hydraulic damper on each side. At the front, the cab sits on flexible rubber bushes.
Over the worst terrain, the entire cab suspension package, hardly a sophisticated one, rode out the bumps with only a small amount of cab nod.
Fully adjustable cloth covered Isringausen 5000 air suspension seats also helped to give a comfortable and relaxing ride.
When charging the vehicle's air system the seats are the last part to receive air. It is a strange way of knowing that the system is almost ready when you begin to rise with the seat.
Despite the biting cold outside, the cab's interior rermained as warm as one cared to make it (for those with a long reach that is, because the controls were too far away for me to adjust comfortably).
The dashboard layout is neat and functional, with its array of warning lights and instruments well sited. However, I much prefer column-mounted switches for wipers, indicators and lights whereas for simplicity and economy Renault fits them to the dash panel.
A useful feature is its headlight-beam height-adjuster switch to the driver's left, behind the park brake lever.
Night driving illustrated the need for a panel light dimmer switch as they were bright. In addition, the large cab-side marker lights distracted me by reflecting smack in the centre of the rear-view mirrors.
Noise levels are a little higher than I expected despite the heavy insulating padding under the cab. The noise meter showed readings of 75dB(A) at 64.4km/h (40mph) rising to 79/80dB(A) at 96.5km/h (60mph), both in top gear.
Cross-cab access is good, with the low broad engine cover allowing ready entry to the bunk area at the back. The plastic moulding across the engine cover needs partitions as items slide away on bends.
Doors which open a full 90 degrees and well-placed handles make entering the cab easy enough. The lower step should be changed for a wider flat sectioned step with a non-slip surface. The present one is of round metal and is angled rather badly.
There was no rain during the three days but melting ice caused some spray which the arm-wipers dealt with easily.
Summary: Production at Dunstable of Renault's G260 is slowly getting under way and has reached three per day. However, the vehicle has yet to establish itself as a serious rival to the leading performers.
Last year Karrier Motors sold 48 and in January this year (never a good month for sales) five only.
Our test showed that when it is operating at 38 tonnes the G260 is a fuel-efficient vehicle, if not as quick as some of its competitors. One can only speculate on its performance at a lesser weight; its journey times would probably improve, but perhaps at the expense of fuel economy. It is type approved at 28, 32 and 38 tonnes.
There is no intention of introducing the MIDR 062045 chargecooled version on the grounds that it will only increase kerb weight and cost. Karrier Motors says that it will also be to the detriment of fuel economy.
The G260 on this form will certainly be of interest to those operators whose vehicles are running just below the 38-tonne limit.