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speed governors?
Page 107
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ST WEEK CM carried out a ries of fuel consumption cornirison trials on the M4 in connction with Volvo (Great -itain) Ltd, and Commercial acovery and Repairs Ltd of 3dfont.
Operating at 32 tons gvw ith our Crane Fruehauf trailer tched to a Volvo F7, we coved 63km (390 miles) in three ages at cruising speeds of 40, 3 and 60mph. We registered a iving of 3.66mpg — that is, 3 per cent — between the top -id bottom speed.
Converted to cash terms, this ould more than compensate r the Budget increase in fuel x and at the same time make a gnificant contributions to fuel :onorny.
The F7 was the right vehicle ir the test. In performance .rms it represents a high proprtion of 32-tonners on the lads of Britain today. It did not aye a large power unit or nring for a high top speed — it as flat out at 62mph — and is pical of vehicles which are just iaximum weight and no more. It had the larger 'F' engine. is is the TO 70, 6.7-litre unit hich is both turbocharged and charge-cooled. It produces 167kW (224bhp) at 2400rpm and maximum torque is 800Nm (590 lbft) at 1400rpm. Volvo's eight-speed range-change box, the R52, was fitted to the vehicle and gave a top speed of 62mph with a rear axle ratio of 4.86 to 1.
The M4 was used for the trials, as we were able to ensure a guaranteed fuel supply nearby at Volvo's Heathrow Centre. In order to do several runs in one day, and to cut down on the overall amount of fuel we required—we didn't want to add unnecessarily to the crisis — we ran between Heathrow and Junction 15, the Swindon turnoff. This is a return journey distance of 211km (131 miles) which was more than sufficient to produce measurable results.
The Volvo had covered 18,716 km (2340 miles) and so was well run-in. It had been maintained according to the manufacturer s schedules by CR and was running nicely.
running nicely
To start with, we carried out the 64km / h (40mph) run, starting from our fuel stations. It was very easy to keep the F7 at this speed — indeed
we never really dropped below it on the motorway. Naturally, though, every other vehicle overtook us and during the whole trip we only overtook one vehicle. We did not present a hazard to other traffic even when the motorway was reduced to two lanes by road works.
The journey took 3hr 34min, giving us an average speed of 57.34km /h (36.64mph) which included the short section of road from the fuel station to the motorway — a distance of about 5km (3 miles). At times it was tedious driving at this speed and our progress seemed very slow.
But the fuel results were complete justification. The Volvo took just 12.5 gallons of dery to top-up, giving a consumption of 27.11it/ 100km (10.42mpg) for this low-speed run.
During the run, the F7 rev counter told us we were running in the most economical band of the rev range, indicated on a segment of the instrument dial at 1700rpm.
Next we tried a run at 60mph. This proved impossible to maintain as the top speed was just 2mph more, so we were running almost flat-out at 2500 rpm and nudging the red sector of the rev counter all the time. Even slight hills brought the speed of the vehicle down to well below 60, often as low as 40.
So although we appeared to cover the ground much more quickly, we did not travel overall much faster than at 40 mph. Indeed the journey this time took 2hr 24min, 1 hr 10min less at an average of 87.8km /h (54.6mph). However, the journey was far less tedious and we were overtaking many more vehicles than overtook us.
Running at this speed took its toll on the fuel. On our return the Volvo had gulped down 19.38 gallons — a consumption of 41.8 lit/100km (6.76mpg).
The final run of the day at 50mph, which turned out to be the best all round. It was enough to keep to the speed — the Volvo had over 10mph in reserve — and yet the rev counter stayed in the green
We held our own with the traffic. While quite a lot of traffic overtook us, we too did our share of overtaking. At this speed, the journey didn't seem interminable, although w something in reserve we na dared to put our foot down!
Nevertheless we maintair our speed and managed average speed of 76.9km (47.8mph) with an accorm nying fuel consumption 35.8lit/ 100km (7.88mpg).1 used 16.62 gallons. Our jo ney time was 2hr 44min just 20 minutes slower than the 60mph run.
Not only did the vehicle sh. dramatic economies at the loy speeds, but the journey tirr were not so very different. 1 F7 is not a noisy vehicle at best of times, but travelling the lower speeds, particularly 40 mph, it was extremely qui In addition to the ft savings, the reduction in wi and tear on the vehicle and si sequent reduced downtime well as lesser likelihood of ma accident damage makes t case for driving more slowl) strong one in financial terms.
It has of course to be ml sured against the additior wage cost for the extra runni time which will result frc slower speeds. At the runni speed of 60mph, or an avera of 54.6, the vehicle will co) 436 miles in 7 hours. To co) the same distance running 50mph, or 47.8mph averaf. will take 9 hours.
In essence this is only o hour of overtime, amounting about £3.00 in wage payme Of course it would be in excr of the new EEC eight-hour day be introduced in January 19 but would be exactly in accc with the nine-hour day bei introduced on July 1 this yea'
Fuel savings at E.1.10 r gallon would amount to £11 per day, or £8.00 per day r after ,deducting increas wages. This, added to the ex savings accruing from less gine and drive-line wear, mak the slower speed economica desirable.
The Government wants a f per cent saving overall. W consumption of 19.38 gallc at 60mph and 16.62 gallons 50mph, the savings were of 1 order of 7 per cent. The benei to all are apparent and we I lieve the wise operator will troduce "speed governors" I fore they are made lec requirements Drivers should ma& aware of the contributi they can make — they are real "speed governors.