For many years the diesel engine has been the forstay of the trucking industry, and has also found application in the taxi and commercial-vehicle fields. Unique Cars and Parts
takes a look at some of the early developments of the Diesel engine which has, for many years, enjoyed healthy sales in Europe and is now making major inroads into the Australian car landscape.
Contrary to what some may believe, there is nothing very new about the diesel. Rudolf Diesel took out the first patent in 1892, stating its advantages over the petrol-vapour engine as a lower fire-risk, lower fuel-thirst and a long service-life.
The latter two attributes are why the diesel power unit has appealed to commercial-vehicle users; the first had some merit for aeroplanes, and was flirted with in aeronautical circles before World War 1. There is also substantial evidence pointing to Rudolf Diesel's desire to use vegetable oils as a fuel in order to help support agrarian society and to enable independent craftsmen and artisans to compete with large industry.
When Diesel's master-patent expired in 1907 some motor companies stepped up their diesel-engine research, particularly during the era when car manufacturers were looking for alternatives to the conventional petrol engine, other designs of note being the Wankel engine and gas-turbine.
The early diffiiculties of making reliable injection pumps and nozzles, and of controlling them, made progress slow and it was not helped by the Inventor, who was lost from a cross-Channel ship when on his way to England in 1912.
By 1923 however, with the great war behind them, automotive engineers were making better progress. Benz of Mannheim had a satisfactory four-cylinder diesel-engine out that year. Although it developed only 45 b.h.p. @ 1,000 r.p.m., it was demonstrated in a huge 5-ton truck.
From this stemmed the notable exhibits at the 1924 Berlin Show, where three diesel engines were shown, a Benz pre-chamber, a MAN direct-injection and a Daimler-Benz air-injection. After Benz had merged with Mercedes in 1926 Daimler-Benz chose to make the pre-chamber type of diesel engine, developed at Mannheim.
They soon brought out the first six-cylinder vehicle diesel engine, which gave 70 b.h.p. @ 1,300 r.p.m. To the three advantages already attributed to the heavy oil engine over the petrol engine was its added ability to develop peak power at comparatively low r.p.m. and the low pollution
factor of its fuel, the latter of growing importance in the climate change obsessed World of today.
The aforesaid long life stems from the fact that the very high c.r. required for sparkless combustion necessitates a rugged bottom-end, while the injection pump is more or less a precision-built component, even if considerable progress was made when Bosch contrived to series-produce such pumps in 1927.
brought out the first diesel-powered passenger car in 1936 and at that subsequent, memorable Berlin Show when Adolf Hitler had GP Mercedes and Auto-Unions running up to it through the public roads, this and a Hanomag diesel were shown. Mercedes remained committed to development of the diesel engine from that point onward, and by 1974 over a million diesel-engined cars had rolled off the Mercedes-Benz production line, that year the diesel engined Mercedes representing 35% of their passenger-car output.
The first diesel truck engines with direct-injection arrived by 1964
. The huge torque and long life of the engine was a distinct advantage, as was the better fuel economy. The OM
403 VI0-cylinder engine was a revelation to the trucking industry, the engine developing 320 h.p. and able to propel the largest commercial vehicles then on the road. In the passenger car sector Mercedes released the 240D, the 91 x 92 mm. four-cylinder 2,404 c.c. engine giving an output of 65 b.h.p. @ 4,200 r.p.m. This was quite a high speed for a diesel engine and although maximum power was not much more than a third of that developed by the 2.7-litre 280E, the petrol engine peaked at 1,800 higher r.p.m, and gave its maximum torque at 2,100 greater r.p.m. than the diesel-powered 240D.
The 5 ton Benz Model 5 truck, pictured here circa 1933, some ten years after an experimental Benz diesel engine had been installed, proving its longevity...
The Problem With Diesel
Given the advantages of a diesel engine over a petrol version, there had to be reasons as to why the former has never dominated the passenger car market. There were actually only 2 main reasons in the early days of the diesel, the smell of the fuel and "diesel knock", particularly when idling. The cost of construction was also against the diesel engine, due to the intricacy of the injection pump and the need for heavy construction throughout the engine.
To help keep manufacturing costs as low as possible the Hesselman six-cylinder heavy-oil engine did without a distribution system, instead having a separate pump for each cylinder, but this was somewhat cheating, using electric ignition to enable a normal c.r. to be used.
But by 1930 Packard
had developed a nine-cylinder radial diesel aero-engine designed by Capt. Woodston which poked out 225 b.h.p. at 1,900 r.p.m. for a weight of 2.27 lb. per b.h.p., from 16-litres, on a c.r. of 16 to 1. rumour has it that the pots on the early Packard
engines were held to the crankcase by stell straps tightened by turn-buckles and that if either broke, all the cylinders flew off. Junkers made good progress with opposed-piston diesel aero-engines, and even in racing circles the diesel engine was proving a force with which to be reckoned.
The Diesel Engine On The Race-Track
In the 1933 Monte Carlo Rally a 1925 3-litre Bentley
fabric saloon driven by Lord de Clifford and using a Gardner 4LW 5½-litre four-cylinder diesel engine developing some 68 b.h.p. @ 1,700 r.p.m. (this having been an experiment by the engine manufacturers, well-known in the marine and commercial-vehicle field) made best performmance by a British entry. A normal 2-litre Lagonda was converted to run on heavy oil, at about this time, by two enthusiasts who were at the Military College of Science at Woolwich. They claimed to have done a 650-mile tour in it at a cost for fuel and lubricating oil of just over 11/- (55p). At Brooklands
, G. E. T. Eyston demonstrated his idea of a diesel-car, with an AEC bus engine of 9-litres capacity in an old Chrysler chassis.
The 45 b.h.p. Benz compression engine of 1923 ...
made a closed racing body for it and although there was then no diesel-class, Eyston took the car, which he called the Safety Special, out in October 1933 and showed the Press that it could do a timed 106.68 m.p.h. over the kilometre. It had a racing exhaust
system, used BP fuel-oil, Castrol lubricating oil and Dunlop tyres, and managed the speed through pouring rain.
Soon after this the FIA introduced a diesel records category, although not divided into capacity classes. Eyston used his front wheel drive
record car "Speed of the Wind" with a Ricardo diesel-engine to break records at Pendine Sands. Later Eyston took the saloon AEC to Montlhery and captured class records up to three hours at nearly 98 m.p.h., having got the 100-mile class record at 102.956 m.p.h. after which a front wheel came off the now-aged Chrysler chassis, while Bert Denly was driving.
In improved form the car took diesel records from 50 km to 24-hours, the last-named record at 94.99 m.p.h. These figures were bettered by others, but in 1937 the AEC-Chrysler re-captured some of its lost honours, with the hour at 105.59 m.p.h., the 12-hours at 97.05 m.p.h. and the 24-hour run done at
R. J. Munday found a use for his old Thomas Special "flat-iron" in 1935, by installing a 2.7-litre 85 x 120.6 mm. four-cylinder Perkins diesel engine of a type called the "Wolf", which was already being tried out in small vans and in a Hillman sedan. This necessitated a raised bonnet, which destroyed the ultra-low appearance of the Thomas Special.
But the results were good. Munday ran for 100 miles at speeds of over 88 m.p.h., the engine having been tuned to give 20 more b.h.p. than its normal 45. With a Zoller supercharger fitted (it is easy to supercharge a diesel engine as there is no problem about whether to blow air or suck mixture, only pure air being involved), the Perkins-Thomas did the two-way kilo. at 94.7 m.p.h., and over 97 m.p.h. in one direction, on some 87 b.h.p.
This was sufficient for the Perkins Company to issue an advertising brochure about the runs and when diesel-records were officially recognised and the Brooklands
figures were accepted.
American driver C. Cummins had brought a Cummins diesel-car to Brooklands
in 1932 and demonstrated it (lap speed, 74.63 m.p.h.), apparently gaining life-membership of the pre-war BARC as a reward. It was a 5.9-litre Cummins V-type engine in a Duesenberg chassis.
At Indianapolis, too, there was notable Cummmins-Diesel activity, up to 1952
. In 1935, encouraged by the success of their Gardner-Bentley in the 1933 Monte Carlo Rally, Gardner's installed their latest idea of what a car-diesel engine should be in a 1932 Lagonda tourer which outwardly looked every bit as good as the standard Lagonda sports car.
The 4LK engine was a light-alloy 3.8 litre four-cylinder unit weighing 684 lb. with starter, and developing 83 b.h,p. at 3,000 r.p.m. on a c.r. of 14 to 1. As nice a piece of machinery as the power unit it replaced!
This diesel Lagonda gave fuel consumption figures of 42 to 48 m.p.g. at road averages of over 30 m.p.h., and it went from 0 to 60 m.p.h. in 24.4 sec. and its top speed on a 3 to 1 axle ratio was 83 m.p.h. - quite an acceptable performance from a petrol-engined sports-car of seventy plus years ago.
From about that time onwards, diesel-engined cars were quickly developed all over Europe, with Citroen
well to the fore with a 1.8-litre Ricardo designed unit, which powered the Yacco Special which was soon to show the world that diesel-records could be taken with quite a small oil-engine.
By 1939, just before the machinations of Hitler stopped progress, the record-book showed that Eyston had the fastest diesel-record, at 159.1 m.p.h. with his "Flying Spray", that a 2-litre Hanomag had done almost 97 m.p.h. for five kilos., and that Yacco held all the long-distance ones, so well-suited to a diesel engine, including eight days at 68.18 m.p.h.
In the production category, Studebaker
were willing to install the 4.7-litre six-cylinder Perkins Panther diesel engine which gave 85 b.h.p. at a modest 2,000 r.p.m. and which was superior to the current Ford V8 30 in respect of weight-per-litre but not weighthorse-power. Whereas Gardner and others had been using injector pumps made under Bosch licence, Perkins had CA V sprayers, a CA V pump and a CA V pneumatic governor on their Panther engine.
Maybe all these things had been anticipated in Europe, for as early as 1923 Peugeot
had submitted to the Press for test two cars identical except for their engines. One had a 2,199 c.c. two-cylinder two-stroke Tartrais-type oil engine of 100 x 140 mm., the other a 2,590 c.c. four-cylinder 85 x 130 mm. petrol engine.
|R.J. Munday's Perkins-powered Thomas Special at Brooklands in 1935, where it exceeded 97 miles per hour with its 2.7 litre Zoller supercharged diesel engine ...
On an identical journey of just over 103 miles, at an identical average speed of fractionally above 32 m.p.g., the oiler returned 19.88 m.p.g., the petrol-engined car 18.87 m.p.g.
Both cars had the same gear ratios and tyre
sizes and the oiler was timed to do a two-way speed of 37.16 m.p.h., the petrol Peugeot 45.48 m.p.h., over a kilometre which did not permit top pace.
The Mercedes-Benz 170D
oil-engined model then created a stir when motoring journalists were able to achieve figures of over 44 m.p.g., and when cruising that figure climbed to just over 62 m.p.g. This was at a time when, in the vast majority of countries, diesel fuel was cheaper than petrol. The 170D
used a 1.8-litre engine giving 38 b.h.p. at 3,200 r.p.m. on a 14 to 1 c.r.
As the price of heavy oil rose to meet that of petrol and when the latter was freely purchaseable, interest in diesel cars on the part of private owners waned. But even though the advantages of a lower priced fuel were no more, the diesel still represented a technology capable of providing far superior fuel economy and, perhaps more importantly, it was better for the environment. Today those reasons alone are enough to ensure the diesel engine enjoys continued sales success in dealerships around the country.