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Extra £112. Says Anthony Ellis THE oil-engined version of the Commer +-ton van costs £112 more than the petrol model, and for this extra sum the operator gets 50 per cent. more m.p.g. at full loads with only slightly inferior acceleration and maximum speed.
It is not surprising, therefore, that about 30 per cent. of the orders received so far for the new forwardcontrol range (described in The Commercial Motor dated January 8, 1960) have been for oil-engined vehicles.
Although the Perkins Four 99 1.621-litre oil engine has been fitted as a conversion unit to other vehicles of this .size, the Commer is the first one in which it is offered as standard. The Four 99 closely resembles the Commer 1.494-litre petrol . engine in overall dimensions and power.
It develops 40.5 b.h.p. net and has a governed maximum speed of 3,600 r.p.m.: in fact, the engine overruns the governor by about 10 per cent., giving a maximum speed of just under 4,000 r.p.m. This power is 8.5 b.h.p. less than the maximum net output of the petrol engine. Peak torque occurs at about 2,200 r.p.m. in both, engines, hut the oiler produces 5 lb.-ft. less than the petrol unit.
Same Mounting Points
Both engines fit into the basic chassis without any modification and use the same mounting points. Transmission ratios and clutch size are not altered for the oiler, which employs the same radiator block as the petrol engine. The only variation for the Perkins unit is in the engine controls. These comprise a combined key operated electrical master switch, starter and Thermostart control, and a stop control mounted on the engine cover beneath the driver's left knee.
E22 The oil-engined van which I tested had a kerb weight of 1 ton 61 which included the optional spare wheel and carrier, two passenger seats and a side-loading door. This was 1+ cwt. more than the similarly equipped petrol-sngined van, my test report on which was also published on January 8. The actual payload of concrete blocks was 101 cwt. which, with two people aboard, brought the gross weight up to the recommended figure of 2 tons 1 cwt.
One of the disadvantages of the oiler is the increased chassis weight, which reduces the permissible payload by 14cwt.
62 Miles in 751 minute
To warm the engine thoroughly I started the test with a high-speed fuelconsumption run on the Ml. Starting from Cornmer's Lut o n factory, 62 miles were covered without stopping in 75+ minutes. This included six miles getting to and from • the motorway and gave an, average speed of 49.3 m.p.h. at a consumption rate of 24.8 m.p.g. The actual motorway section of 56 miles was completed at an average speed of 55 m.p.h.
The highest speed achieved and Jheld for long periods was 60 m.p.h., whilst the lowest speed was 48 m.p.h. Theoretically, governed maximum speed for the oiler is 53.5 m.p.h., but governor overrun increases this to the higher figure, making the actual maximum speed only 4 m.p.h. less than that of the petrol-engined mode! fitted with the same 5.125-to-l-ratio rear axle.
The motorway run was identical to that carried out with the petrolengined van. I achieved a higher average speed with the oiler mainly because the governed engine seemed to be running without strain at peak revolutions. Whilst the petrol engine was driven at just below full throttle, the oiler •was on full throttle all the time.
This had no ill effects on the engine, but, on coming off the motorway, appeared to have upset the slow running setting of the distributor-type injection pump, which had to be adjusted.
Normal consumption runs followed on our six-mile A6 circuit between
I3arton and Clophill. Here the Commer showed that on non-stop laden running it would give 416 m.p.g.: a clear 50-par-cent. improvement over
the petrol-engined Van. Even on four-stops-per-mile runs with the engine idling for 15 seconds at each halt a 30-per-cent. improvement was noted.
The differential between the consumption rate of the petroland oilengined vans rose sharply as the load was reduced, reaching nearly 80 per cent. on the non-stop unladen run, with a consumption rate of 53.93 m.p.g, at an average speed of 30.5 m.p.h.
Although all starts during these runs were made in first gear, the van would pull away on the level quite easily in second gear, indicating that the 5.125-to-1 axle is well matched to this engine. Only for consistent overloading or exceptional gradient ability would the optional 5.625-to-1 ratio be an advantage.
Cooling effectiveness was checked on Bison Hill, near Whij3snade. This 3-mile-long incline has an average gradient of 1 in 12 and was climbed in 2 minutes 20 seconds-20 seconds less than the time returned by the petrolengined van. This was because of the superior low-speed pulling of the Perkins engine, which eliminated the need to change into first gear. Second gear was engaged for 45 seconds.
It was impossible to check the coolant temperature before and after the climb, as I had no thermometer but, on removing the radiator filler cap at the top of the hill, it was obvious that the system was far from the limits of its cooling capacity.
Indeed, there should be no cooling problems with the Perkins engine, as it is, by its nature, a cooler-running unit than the petrol engine but employs the same radiator block. Water capacity is less, however, as the cylinder block and head of the oil engine have smaller coolant passages.
The van re-started with ease on the I-in-63 section of the hill at low throttle in both first gear and the slightly lower reverse ratio. Its theoretical maximum-gradient ability is 1 in 43, which would be increased to well under j in 4 when the optional low-ratio-axle was fitted.
Usually oil-engined versions of petrol-engined vehicles suffer severely on comparative acceleration. This is far from the case with the Commer. Through the gears, from 0-40 m.p.h., the oiler was only 3 seconds slower than the petrol-engined model, whilst
the time from 10-40 m.p.h. in top gear was quicker by 13 seconds.
Considering the lower power of the oil engine, these figures would appear to indicate that the gearbox ratios employed for both engines tend to be slightly more suitable for the Perkins unit.
In direct drive, the engine would run happily with the clutch fully engaged at a road speed of about 6 m.p.h., and would then accelerate smoothly from this speed without protest from the engine mountings or the transmission. Maximum speeds in the indirect gears were 14 m.p.h. in first, 25 m.p.h. in second and 38 m.p.h.. in third.
Noise level in the cab is fairly low. Up to about 35 m.p.h. some of the normal oil-engine noise is heard, but this is not objectionable and does not drown conversation. Above this speed the noise emanating from the engine compartment. rises. Most of it appears to come from the fan, as a proportion is also present in the petrol-engined vehicle.
It seems a pity that the fan shape could not be improved to eliminate this, or, alternatively, that more liberal use could not be made of sounddeadening materials on the interior of the engine covers.
As in. the petrol van the engine in the Commer oiler is easy. to get at for the infrequent maintenance which it should require. Removal of the detachable panels at each side of the engine compartment, w hi ch are secured by rather too many screws, gives access to both sides of the power unit. Even without removing the panels there is plenty of space around the engine.
I was pleased to see that Perkins have dropped the screw-type injector fitting introduced for the Four 99 and have reverted to their normal lug-andstud mountings.
For those who could operate it for fairly large annual mileages, under which conditions the additional extra cost would soon be recouped. the Commer oil-engined van is good value at its basic price of f611.