The new front-wheel drive, the LP series of 1963 are just a year old, since you and also your short-haubigen colleagues new engines. Daimler-Benz says the 1923 introduced pre-chamber principle, a good 40 years farewell and introduced in 1964 in the shape of two new in-line six-cylinders, direct injection: The 10.8 litre OM 346 and the OM 352 with 5.7 liters of displacement from the pre-chamber diesel OM 326 and OM 322.
OM 322 is replaced by OM 352
“In a long-term development work, it is possible to combine the favourable fuel consumption of the direct-injection method with the advantages of the precombustion chamber system.“ With these words and the following note on “year long testing“ the work of the new units. And trying at the same time, concerns whether hard Nailing (at the time injectors, the Crux of the matter for many), or dispel the lack of stability of the new engines.
At least the 126-HP predecessor engine OM 322 held the warranty on your toes. Also 126-HP successor, the OM 352, however, remains of children’s diseases, almost spared, and the OM 322 overall, in terms of reliability right off the bat in the shadows. Three things there are, Essentially, speak for the farewell to the traditional pre-chamber engine: around 15 percent of the new injection procedure to decrease the consumption. Although the price of Oil is at that time a Barrel is still under two dollars, and should not exceed that mark until 1973. However, climbing the fiscal burdens for Fuel significantly. The proportion of tax per litre of Diesel is from 1950 to 1960 almost four pfennigs (the equivalent of about two cents), he rises from April, 1960, with nearly 23 pfennigs per litre (the equivalent of about twelve cents), almost six times and is from the new year, 1964, with a good 35 pfennigs (the equivalent of around 18 cents) per litre more than 50 percent higher. There’s a 15 percent reduced consumption, therefore, is music to the ears of the conveyors.
Direct injection without using the starter
In contrast to the precombustion chamber engine of the direct injection engine does not start. At least as long as the temperature range is below minus 15 degrees Celsius. From then on, only the driver now engages with the so-called Start-Pilot: those usual setup, which is a carbon-hydrogen contributing compound in the intake tract, which causes a immediate Start of the engine. The third in the trio of the great advantages of direct injection is that it developed as a result of more efficient combustion is much less soot than the pre-chamber engine.
Although the engine weight and the bore and stroke of OM 346 and the OM 352 and the power are identical with the values at the predecessors. However, the technology is presented in Detail completely different: prechambers and glow plugs are eliminated. The combustion chamber is now housed in the piston. And the suction channels are re-designed. Instead, in a split combustion chamber, the Diesel is now a Beeline course to the walls of the Piston bowl. Appropriately designed Intake ports have, meanwhile, moved in the cylinder by the incoming air in a Rotation, the compression stroke is amplified again (due to the smaller diameter of the Piston bowl).
Just in this vortex of air the four-hole scramble jets, their fuel, what the standards of the time “an excellent treatment of the fuel-air mixture“ results. “Favorable thermal conditions“emphasizes the work presented in this way also, and were the “the guarantee for a long service life“ .
Both units work according to the same principle, but the Layout of the injection and cylinder heads in each case is quite different: Sitting at the larger engine (by the way, like its predecessor, the OM 326 is a four-valve engine), the injection nozzle centrally and vertically, so it is the two-valve engine OM 352 is inclined, and with a certain offset from the piston center arranged. And the OM 346 comes with single-cylinder heads, the six-cylinder OM 352 sitting in the attic of a single, common cylinder head.
More Freedom From Maintenance
A further advantage of the new engines is that the injection pumps Shine via connection to the engine oil circuit with no need for maintenance. The main flow oil filter, a so-called ultra-fine filter in the oil supplemented in addition to current, the hoist, the oil change intervals on the at the time proud, with a value of 9000 kilometers. The OM 346 – incidentally, like its predecessor, the OM 326 is a four – cylinder is available in two capacity variants: 180 and 202 HP at 2200 rpm. The maximum torque at 1300 rpm and is 608, respectively, 706 Newton meters.
Even the 210 HP for the stronger variant is then to beech, if it is provided with a thermostatically controlled Viskolüfter that is so, if necessary, to the fact. As a driving force in the 10.8 litre OM 346 of the acts in the heavy bonnets and front arms of the German: gaggenauer plant, as well as in the buses O 317 O 317 K. the Interesting aspect is the division of labor between the two power variants: For the medium-haul traffic and gross combination weights of up to 30 tons, Mercedes-Benz offers the relatively lightweight LP 1418 for 14 tons total weight of the motor car, its low weight made from lightweight five-speed gearbox (combined with the lightweight two-speed rear axle for a 9.8-tonne load capacity) and a slender Chassis, as well as smaller clutch results.
Instead of a two-circuit pressure-air brake, as in the case of the 16-Tonners for long-distance transport, the plant provides the 1418 with two-circuit hydraulic brake, but has the aid of compressed air. All in all, this is an affordable vehicle with a relatively large amount of payload. The real long-distance transport steamer LP 1620 is designed for gross combination weights of from 32 to 38 tons. The addressee of the new OM 352, however, are the medium-duty Mannheim Truck with the types of shortcuts, 1113 and 1114, as well as the buses to the O 321 H/HL, and O 322. The OM 346 draws from 5.7 liters of displacement exactly 126 HP, the rated speed 2800/min. Its maximum torque of 353 Newton meters, the OM reached 352 at 1600/min.
OM 352: up in the 80s in the use of
Both engines have a long career ahead of you. The 5.7-Liter unit, for example, strengthened starting in 1966, as charged OM 352 A to 150 HP, comes later, even with 170 HP, and works up in the 80s, not only in Truck and Bus, but also in the Unimog.
Even longer, the OM 346 live incognito, but to a certain extent: in the year of 1967, he adopts, by increasing the stroke from 140 to 150 mm 11.6 litres of displacement brought, the name of the OM 355. As such, he can come up in the beginning with 230, starting in 1969 with 240 HP and has to give way in Europe, however, already during the 70s, the new V-engines from the 400 series.
In the still and all the same until 1994, busily export bonnets-terminated Short, he is a welcome guest in distant countries. Either as a sucker with a 240 or a turbo engine with 280 HP, it performed in these bonnets à la 1924 or 1928 of reliable service. And also Overseas, the Brazilians know, for example, to estimate the OM 355 a lot. There, he brings it also to a decades-long, and achieved with turbo charging and charge air cooling from 1988, not 340 HP.
Source: Daimler AG
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