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Onderwerp: From Wankel to Diesel

From Wankel to Diesel 23 okt 2009 23:46 #5021

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From Wankel to Diesel









In September 1969, worldwide attention focussed on the C 111 experimental vehicle, which Daimler-Benz presented at the International Motor Show in Frankfurt. This "rolling test laboratory" was a highly conspicuous affair, with its extreme wedge-shaped body, gullwing doors that opened vertically and last but not least, its unusual colour, metallic orange. Just a handful of the cars were produced.



The technical innovations were not quite as obvious: the body consisted of glass fibre reinforced plastic and was riveted and glued onto a steel framework. Some technical features from racing cars were applied to the wheel suspension and last but certainly not least, the car was powered by a three-rotor Wankel engine!
This engine developed some 280hp and allowed the car to reach a maximum speed of 270 km/h. Both figures were remarkable feat at that time.



Only six months later, a highly revised version of the experimental car was presented at the Geneva Motor Show. The new C 111 had a more pleasing body giving better vision and a roomier baggage compartment. It was powered by a four-rotor 350hp Wankel engine, which gave excellent driving performance: it reached 100 km/h from a standstill in 4.9 seconds and went on to a top speed of 300 km/h.





Although there were many orders and even blank cheques from potential buyers for the car at the factory in Untertürkheim, the C 111 remained a purely experimental vehicle and never went into production.
The super sports car was a favourite object for exhibitions in Germany and abroad and for a long time guaranteed a high level of publicity. Even after Mercedes interest in the Wankel engine had almost passed into oblivion, the C 111 was in the public limelight several times.



In June 1976, in April 1978 and for the last time in May 1979, record speeds were achieved with the C 111 at the high-speed circuit at Nardo in the South of Italy, culminating in several absolute world records over various distances.






Racing diesel in keeping with the times




Once the first shock of the oil crisis had been overcome, the Wankel engine was replaced by a diesel engine – a policy pursued by the entire industry since the diesel was known to be economical. On the other hand, it was also generally known to be a lame duck – a view that was not completely unjustified. Something had to be done about it, and the development engineers and Board of Management came up with the idea of establishing sales-promoting diesel records.

The basic engine which suggested itself was the powerful, five-cylinder three-liter naturally aspirated diesel from the 240 D 3.0 and 300 D, an engine with plenty of potential for raising performance. With a Garret turbocharger and an intercooler, the production engine’s output of 80 hp was boosted to a proud 190 hp to power the C 111-II, revamped into a diesel-engined record car, in the record run on the brand-new test track in Nardo on June 12, 1976.




The four drivers, who took turns at two-and-a-half hour intervals, drove this car from one diesel record to the next over a time-span of 60 hours, completed without any problems. In the end, a total of 16 new records had been established – those over 5,000 miles, 10,000 kilometers and 10,000 miles even were absolute world records, i.e. independent of the type of engine. Speed averaged around 252 km/h. So the diesel had proved its ability to race, and with a suitable ratio, the C 111-II completed the sprint from standstill to 100 km/h in just 6.8 seconds.

The records established by the C 111-III

For those involved in the project, this was just the beginning, however. They knew they could have made the car even faster, raising its top speed to over 300 kilometers per hour, but had to admit that this was meant for an aerodynamically optimized “proper” racing car rather than for a road-going version of the C 111. The Board of Management at the time has to be credited for sharing this view and giving the go-ahead for development.

The design department set about its task in early 1977 and created the C111-III on the basis of the C 111 team’s specifications – a thoroughbred racing car with aerodynamic features refined down to the smallest detail and giving the car a Cd value of 0.183, the lowest rating ever achieved up to that point in time.



The car had a longer wheelbase than the C 111-II, a narrower track, concealed wheels, a very low front end with recessed, powerful headlamps and a very long and tapering rear end with a central fin that was to enhance the car’s straightline stability under side wind conditions.

The long and narrow driver’s compartment featured a single seat: the front passenger’s space was occupied by a fat pipe conducting air into the intercooler. And there was also room for the telemetry system, specially developed by Mercedes-Benz for automatic data transmission during the record runs, as well as for radio equipment, enabling the driver to communicate with the team on the move.

And finally, on April 30, 1978, the time had come for the diesel-engined record car to drive lap after lap at constant speed on the Nardo track – anti-clockwise because this meant that the track-defining crash barriers were on the right-hand side, providing the drivers of the LHD cars with a greater safety margin in the event of an accident. At one stage during the night, radio communication saved a hedgehog’s life: it was rescued in time before crossing the racing car’s lane. When the rear tire on the right-hand side burst during the third driver’s stint at night-time, tearing large holes into the bodywork, the recovery truck arrived on the scene quickly to pick up the damaged car and its uninjured driver, while the mechanics prepared the identical reserve car. After this incident, clocks were reset to zero and the hunt for records began anew.

The reserve car was even a whisker faster than the original car, and also a little more economical, extending the refueling intervals from 62 to 67 laps. The three drivers were soon joined and relieved by their extremely fast project manager, Dr. Hans Liebold.

All records established by the time of the tire damage were repeated at even better times, and the attempt was not even jeopardized by another hedgehog which was unfortunate enough to get in the record car’s way and ruined its front spoiler. The repair took no more than two minutes. The pit stops, incidentally, lasted between 15 and 20 seconds – the refueling, driver changes, tire checks and topping up of oil had all been meticulously planned and thoroughly practiced.

After 12 hours of otherwise problem-free driving, the Mercedes-Benz brand called nine new absolute world records its own, i.e. records irrespective of the type of engine and its

displacement – achieved with a near-production three-liter diesel engine. At the end of the day, the engine in the record car had consumed just under 16 liters per 100 kilometers – another outstanding record given an average speed of over 300 km/h.

The world records established by the diesel-engined C 111-III:
100 km: 316.484 km/h100 miles: 319.835 km/h500 km: 321.860 km/h500 miles: 320.788 km/h1000 km: 318.308 km/h1000 miles: 319.091 km/h1 hour: 321.843 km/h6 hours: 317.976 km/h12 hours: 314.463 km/h


World circuit record: 403.978 km/h

A world circuit record of 355.854 km/h had been in existence since 1975, established by a 1,000 hp racing car from the American Can-Am series. Though not recognized by FIA, it was a highly desirable world record, and after the successes with the C 111-III, the Mercedes-Benz engineers felt that it was within reach. Just another 100 hp would do – but could no longer be squeezed out of the near-production diesel. So the team opted for the 4.5 liter V8 gasoline engine from large-scale production, raised its displacement to 4.8 liters and equipped the unit with sodium-cooled valves, two KKK turbochargers and a triple-plate clutch that was capable of coping with 600 Nm torque.

With 500 hp under the hood, achieved at relatively low expense, a C 111-IV modified into a racing car with further aerodynamic improvements, two fins and additional spoilers set out in Nardo on May 5, 1979 to have a go at the world circuit record. After a smooth run, a new record of 403.978 km/h had been established. Over and above this, the car improved upon the record marks over ten and 100 kilometers as well as over ten and 100 miles.
The C 111 must be one of the very few research cars ever powered by such an array of engines - from triple rotor through to five-cylinder diesel to twin turbocharged V8!

C 111 Specifications (First Version)



Engine
Combustion principle Wankel
Configuration in front of rear axle (mid engine)
Engine type M 950 F
Number of cylinders / arrangement three-rotor Wankel engine
Total displacement chamber volume 3 x 600 cc
Compression ratio 9.3
Rated output 280 hp / 206 kW at 7000 rpm
Rated torque 294Nm at 4000 - 5500 rpm
Fuel system direct injection, mechanically controlled; Bosch 3-plunger injection pump
Cooling water cooling / pump; radiator in the car's front
Lubrication pressure circulation lubrication
Electric system 12 V
Generator three-phase AC
Starter electrical
Ignition transistor ignition
Fuel tank: position / capacity in the lateral frame side rails / 2 x 60 litre
Fuel supply piston pump as part of the injection pump


Body & Suspension



Frame design sheet steel floor assembly / fibreglass reinforced plastic bodywork
Front-wheel suspension double wishbone-front axle with torsion bar stabilizer
Rear-wheel suspension per wheel three wishbones and two trailing arms
Front springs spring struts, torsion bar stabilizer
Rear springs spring struts, torsion bar stabilizer
Shock absorber front/rear telescopic shock absorbers
Steering recirculating-ball steering
Brake system hydraulic dual-circuit brake system with vacuum booster; internally ventilated four-wheel disc brakes
Parking brake mechanical (manually operated), acting on rear wheels
Wheels sheet-steel wheels or light-alloy wheels
Tyres 195 VR 14
Driven wheels rear wheels
Drivetrain final-drive assembly and differential in unit with transmission

Gearing & Performance



Gearing 5-speed manual transmission ZF 5 DS-25/1
Shifting central floor gear shift lever
Clutch dry single-disc clutch
Synchromesh gears I - V
Final drive ratio 3.166
Maximum speed 260 km/h
Acceleration 0-100 km/h 5 sec (2 occupants)


C 111 Specifications (Second Version)



Engine
Combustion principle Wankel
Configuration in front of rear axle (mid engine)
Engine type M 950 F
Number of cylinders / arrangement four-rotor Wankel engine
Total displacement chamber volume 4 x 600 cc
Compression ratio 9.3
Rated output 350 hp / 257 kW at 7000 rpm
Rated torque 392Nm at 4000 - 5500 rpm
Fuel system direct injection, mechanically controlled; Bosch 4-plunger injection pump
Cooling water cooling / pump; radiator in the car's front
Lubrication pressure circulation lubrication
Electric system 12 V
Generator three-phase AC
Starter electrical
Ignition transistor ignition
Fuel tank: position / capacity in the lateral frame side rails / 2 x 60 litre
Fuel supply piston pump as part of the injection pump

Body & Suspension



Frame design sheet steel floor assembly / fibreglass reinforced plastic bodywork
Front-wheel suspension double wishbone-front axle with torsion bar stabilizer
Rear-wheel suspension per wheel three wishbones and two trailing arms
Front springs spring struts, torsion bar stabilizer
Rear springs spring struts, torsion bar stabilizer
Shock absorber front/rear telescopic shock absorbers
Steering recirculating-ball steering
Brake system (Foot brake) hydraulic dual-circuit brake system with vacuum booster; internally ventilated four-wheel disc brakes
Parking brake (Hand brake) mechanical (manually operated), acting on rear wheels
Wheels sheet-steel wheels or light-alloy wheels
Tyres 205 VR 14; for racing: front: 4.50/11.60-15; rear: 5.50/13.60-15
Driven wheels rear wheels
Drivetrain final-drive assembly and differential in unit with transmission
Gearing & Performance
Gearing 5-speed manual transmission ZF 5 DS-25/1
Shifting central floor gear shift lever
Clutch dry double-disc clutch
Syncromesh gears I - V
Final drive ratio 2.975
Maximum speed 300 km/h
Acceleration 0-100 km/h 4.8 secs (2 occupants)
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Re:From Wankel to Diesel 24 okt 2009 13:29 #5031

  • Ray
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Mooie proto!! Love it!!
Zoals je ziet is al het mooie al een keer gemaakt :P ....

Knap stukje zoekwerk Maurice en voldoende leesvoer haha!!
Echte liefde roest niet, mijn Renault wel! | Het mag stuk gaan.... Als het maar hard gaat!
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