Mercedes-Benz OM 617
| Mercedes Benz | |
|---|---|
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| OM 617 | |
| Manufacturer: | Mercedes Benz |
| Production period: | 1974-1992 |
| Design: | Inline five-cylinder |
| Engines: | 3.0 liters (3000 cm³) 3.0 liters (2998 cm³) |
| Previous model: | none |
| Successor: | Mercedes-Benz OM602 |
The OM 617 is a five-cylinder in - line engine from Daimler-Benz . The diesel engine with prechamber injection came on the market in 1974 in the Mercedes-Benz 240 D 3.0 ( "Stroke-Eight" , W 115). It is derived from the four-cylinder OM 616 engine and only differs from it in the additional cylinder .
The abbreviation "OM" stands for "Oel-Motor" (engine that runs on light oil / diesel). Thanks to the modular system, it has the pistons and connecting rods in common with the OM 616 (240 D) . In the development was Ferdinand Piech , grandson of Ferdinand Porsche and subsequent CEO of Volkswagen AG , a major role. From 1972 he ran an engineering office in Stuttgart and later also built five-cylinder engines for Audi .
Use in models
- W 115 240 D 3.0
- W 116 300 SD turbodiesel (for US export)
- W 123 300 D
- W 123 T 300 TD
- C 123 300 CD diesel and turbodiesel (US export)
- W 123 300 D turbodiesel (US export)
- W 123 300 TD turbodiesel (also home market)
- W 126 300 SD turbodiesel (US export)
- Puch / Mercedes G 300 GD
- Mercedes-Benz T 1 (209 D, 309 D, 409 D)
- C111 Type II (prototypes and experimental vehicles)
Data
- Bore : 91 mm
- Stroke : 92.4 mm
- Displacement : 3005 cm³
- Compression ratio : 21: 1
- Output: 59 kW (80 PS ) at 4000 rpm
- Torque: 172 Nm at 2400 rpm
- Maximum speed: 5100 rpm
In August 1979, with the same stroke, the bore was slightly reduced by 0.1 mm in order to reduce the displacement below the tax-relevant level of 3000 cm³, while increasing the output by 10 through higher compression and a modified cylinder head with steeper camshaft and other pre-chambers % increased:
- Bore 90.9 mm
- Displacement: 2998 cm³
- Compression 21.5: 1
- Output 65 kW (88 PS) at 4400 rpm
- Torque unchanged at 172 Nm at 2400 rpm
The five-cylinder naturally aspirated diesel in the 300 D of the W 123 series thus had performance comparable to that of the weakest four-cylinder gasoline engine with 69 kW / 94 hp in the Mercedes 200.
Turbo variants
As early as May 1976, under the project management of Hans Liebold, the first world record runs with a modified C111 / 2 with OM 617 ATL ( exhaust gas turbocharger ) and an output of approx. 140 kW took place in Nardò (Italy). The average speeds achieved were around 250 km / h.
In May 1978, the newly built record vehicle C 111/3 again set long-distance world records with the OM 617 ATL, whose output had meanwhile been increased to 170 kW. In combination with the extremely streamlined body of the C 111/3 a c w value of 0.18, the average speed could be increased to over 320 h km /.
With the T-model (station wagon) of the middle class 300 TD turbodiesel from the 123 series , the turbo engine came up in a version with 92 kW (125 PS). The motors achieve a torque of 250 Nm.
Shortly before, turbocharging was offered as standard for the American market in the 300 SD Turbo ( 116 series ) from 1978 . This approach corresponds to a model that has often been tried and tested at Daimler-Benz when changing technology and model series: a new technology is introduced in a limited market segment (USA), and if it proves its worth there, the technology is introduced shortly afterwards in other markets or other model series . This strategy minimizes cost problems in the event that difficulties should arise, for example with regard to reliability and warranties.
Other brands such as BMW, Alfa Romeo, Audi etc. only later offered comparable powerful diesels, such as BMW from 1983 the 2443 cm³ six-cylinder M21 with 85 kW, Audi from 1982 a 74 kW two-liter five-cylinder turbo with intercooler and from 1990 the 88 kW 2.5-l TDI.
OM 617.950 (Turbo OM 617 A, A = exhaust gas powered charger) in 1979:
- Bore 90.9 mm, stroke 92.4 mm, displacement 2998 cm³
- Compression 21.5: 1
- Output 85 kW (115 PS) at 4000 rpm
- Torque 250 Nm at 2400 rpm
- Maximum speed 5200 rpm
OM 617.952 (Turbo OM 617 A) in 1982:
- Bore 90.9 mm, stroke 92.4 mm, displacement 2998 cm³
- Compression 21.5: 1
- Output 92 kW (125 PS) at 4350 rpm
- Torque 250 Nm at 2400 rpm
- Maximum speed 5200 rpm
This turbocharged engine was the first diesel engine to be found suitable for use in the bodies of the S-Class and mid-range coupés - Daimler-Benz was concerned with complying with the fleet consumption values specified by US governments. The 300 SD (S-Class Diesel) and 300 CD (Diesel-Coupé) models were created, their first ( S-Class W 116 , Coupé C 123 ) and second body versions ( S-Class 126 series , Coupé C 124 ) were only sold in the US.
In these first diesel turbo engines for Mercedes cars, spray oil-cooled pistons were used. They are the first series engines in the world to have plain bearings from the manufacturer Glyco , in which an uppermost load-bearing hard layer was applied by sputtering to the steel carrier layer, the bronze bearing layer and the galvanic coating in a vacuum . Because of its hardness and wear properties, this technology has since been used in series in many high-performance engines. Attempts to tune diesel engines have often failed with engine damage due to insufficient piston cooling and weak crankshaft bearings that could not withstand the higher combustion pressures.
Development and problems
Some engines from the first series had problems with the casting quality of the engine housing, which is now longer by the fifth cylinder. There were also problems with the turbos at the beginning - the high pressures on the crankshaft bearings led to various damage. Daimler-Benz then used plain bearings with a sputtered layer for the first time in these engines (see above) .
In this engine, for the first time in passenger car diesel engines, Daimler-Benz used crankshafts which - after forging in one plane - are still "twisted". Twisting is the twisting of the crank pin in order to achieve an even ignition offset of 144 degrees in the five-cylinder. (In the case of six-cylinder shafts, four of the six crank pins are twisted by 60 degrees, which can be done more cheaply than the pin offset of five-cylinders.) For this purpose, after forging and trimming the blank of the five-cylinder shaft, four of the cranks are each increased by 36 Degrees hydraulically raised or lowered from the forge level. This makes the five-cylinder crankshaft a considerably more complex component compared to a four-cylinder shaft.
The first turbos were sometimes unable to cope with high continuous load at high outside temperatures. B. on the highway at a rest area, the engine is turned off immediately. The housing, which glowed dark red from the high exhaust gas volumes at full load, then heated up the entire charger including the turbine shaft and the oil, with the result that the oil in the shaft bearings coked and blocked the charger.
Later, there were specific instructions in the operating instructions that the turbo-diesel engines must first be "cooled down" after driving at full throttle or that they must not be switched off directly from the high load state, but only after a few minutes of cooling after-run at a lower load.
Both the large first-generation naturally aspirated diesel engines and, above all, the turbos, with their large displacement of three liters, moved noticeably away from the old diesel reputation for economy. Experience shows that the 59 kW variant and the turbo can hardly be moved below approx. 10 l / 100 km (also due to the standard automatic transmission). It was not until the 65 kW variant with manual gearbox, especially with the five-speed gearbox available from 1982, that the three-liter diesel with less than 9 l / 100 km achieved consumption values that were well below the small gasoline engines of that time.
Another advantage of this diesel generation has been striking since the late 1990s: Like its four-cylinder sister engines and the subsequent generation of diesel engines, the OM 617 is ideally suited for operation with vegetable oil. With the original injection nozzles (Bosch DN0SD220), the cold start properties are relatively poor. However, the front jet nozzles (DN0SD261 / 265/314) from the W 124 can be installed without any problems , which also improves the cold start. Regular exhaust gas testing proves that the turbidity values, which are still quite high for this generation, can be reduced considerably by using vegetable oil.
Compared to more modern diesel engines, it is noticeable that the OM 617, like its model series siblings, still works quite rough. The five-cylinder, especially in the series in which it was used before the six-cylinder three-liter ( USA models of the S-Class W126 ), cannot keep up with the subsequent OM 603 engine in terms of comfort and consumption data. The advantage of the older engine type, however, is its comparatively insensitivity to damage to the cylinder head gasket, since the cast material of the engine housing and the cylinder head in the OM 617 are still identical, whereas the successor has an aluminum cylinder head with a consequently different expansion behavior.
