Press Information

At the Geneva Motor Show in March 1980, Mercedes-Benz presented the SL and SLC in updated form. Their interior appointments, including the steering wheel were harmonised with those of the 126-series S-Class, and the engineering was brought up to the same level. The previous three-speed automatic transmission with torque converter was replaced with a four-speed variant. Models 280 SL and 280 SLC were given a five-speed manual transmission as basic equipment. In addition, the hardtop was now included in the standard specifications of the open-top variant. But above all the light-alloy eight-cylinder engines of the 126-series S-Class, slightly modified, made their arrival in the 107-series. The six-cylinder engine of the 280 SLC remained unchanged.

The new 500 SL, equipped with the 5.0-litre V8 (M 117) familiar from the 450 SLC 5.0, replaced the 450 SL and delivered an output of 177 kW (241 bhp) at 5000 rpm, to give the new top-of-the-range model a 0 to 100 km/h acceleration of 7.8 seconds and a top speed of 225 km/h.

Models 350 SL and 350 SLC were sent off into retirement after nine years of production. Their successors were the 380 SL and 380 SLC, whose 3.8-litre light-alloy engine (M 116), with 160 kW (218 bhp) at 5500 rpm, originated after the pattern of the five-litre unit, by enlarging the bore of the long-serving 3.5-litre V8 with grey cast iron cylinder block. Both models attained top speeds of 215 km/h and accelerated to 100 km/h from a standstill in just 9 seconds. From the outside the new models were almost indistinguishable from the previous models, except for the badge with the model designation. All three SL models had now a light-alloy bonnet and the discreet front spoiler familiar from the 450 SLC 5.0; the 500 SL was also given a light-alloy boot lid with a black plastic rear spoiler, already familiar from the five-litre coupé.

In autumn 1981, both V8 engines were thoroughly redesigned in the context of the “Mercedes-Benz Energy Concept” to reduce their consumption and pollutant emissions. Along with an increase in compression ratio the measures included camshafts with variable valve timing, air-bathed injection valves, and an electronic idling speed control. Owing to the altered camshaft tuning the maximum torque could be shifted to a lower engine speed range and, in the case of the 3.8-litre engine, even increased. This power plant underwent particularly far-reaching changes: to get a more favourable volume-to-surface ratio the bore was reduced and the stroke increased. The modified 3.8-litre V8 thus had a slightly larger displacement. In both eight-cylinders, in exchange, so to speak, for the improved economy, minor losses in power had to be accepted, output dropping to 150 kW (204 bhp) at 5250 rpm in the 380 SL and to 170 kW (231 bhp) at 4750 rpm in the 500 SL. As in the 126 series the final drive ratio was adjusted to the changed engine characteristics and made higher, from 3.27 to 2.47 in the 380 SL and from 2.72 to 2.24 in the 500 SL.

For the SLC Coupés these changes came too late, however: at the Frankfurt on the Main International Motor Show in September 1981, along with the “Mercedes-Benz Energy Concept” the 380 SEC and 500 SEC models of the C 126 series were presented, spelling retirement for the SLC models, which had been built for exactly ten years.

But even after ten years of production there was no thought of a replacement for the SL models; what’s more, four years after the Energy Concept was presented, they came in for extensive refinements, and so in September 1985, again at the Frankfurt show, a completely revised SL model range was introduced. The emphasis was on a restructured engine range. A discreet facelift, primarily recognisable from the front spoiler and wheels with aluminium rims (diameter: 38.10 centimetres), was also part of the package. The front axle was reworked and the brakes enlarged with fixed callipers. To prevent the cars from pulling to one side when braking, the steering offset was reduced.

A comprehensive facelift

All engines were available in two versions: with a catalytic converter and slightly lower output, and as so-called catalyst retrofit version without a catalytic converter. The catalyst retrofit versions could be equipped later on with a catalytic converter, for example when the widespread supply of unleaded petrol was ensured, and had their ignition system, electronics and cable harness prepared for this.

A newly-designed 3.0-litre six-cylinder engine (M 103) which had made its first appearance in the 300 E of the mid-range W 124 series nine months earlier replaced the tried and tested 2.8-litre engine, as it had already done previously in the respective S-Class Saloon. As a result the 280 SL was discontinued, and after a 22-year interruption there was again a sports car with the magic model designation 300 SL. It delivered an output of 138 kW (188 bhp) at 5700 rpm without catalytic converter (top speed: 203 km/h; 0 to 100 km/h in 9.6 seconds) and 132 kW (179 bhp) with catalytic converter (200 km/h; 9.9 seconds).

A new addition to the range was the 420 SL with the 4.2-litre V8 engine (M 116), which delivered 160 kW (218 bhp) at 5200 rpm without a catalytic converter and 150 kW (204 bhp) with one. It was created by adopting the bore of the original 3.8-litre engine and combining it with the stroke of the “Mercedes-Benz Energy Concept” 3.8-litre engine, and it now replaced that unit in the SL, the S-Class Saloon and the SEC Coupé. The 420 SL accelerated from 0 to 100 km/h in 8.5 seconds (with catalytic converter: 9 seconds) and reached a top speed of 213 km/h (205 km/h).

The 5.0-litre engine (M 117) was modified, too; with catalytic converter operation in mind it now had an electronic ignition system and the electronically/mechanically controlled Bosch KE-Jetronic injection system, delivering 180 kW (245 bhp) at 4750 rpm. With a catalytic converter the output was 164 kW (223 bhp) at 4700 rpm. These values helped the 500 SL reach a top speed of 225 km/h (with catalytic converter: 215 km/h) and accelerate from 0 to 100 km/h in 7.3 seconds (7.8 seconds).

The most spectacular new development in the engine range was a 5.6-litre eight-cylinder engine (M 117), which was created by increasing the stroke of the 5.0-litre V8 and which gave the SL an output of 170 kW (231 bhp) at 4750 rpm. The 560 SL was reserved for the USA, Australia and Japan export markets. Fitted with an emission control system in the US version it had a top speed of 223 km/h and sprinted from 0 to 100 km/h in 7.7 seconds.

Production of the R 107 series ended in August 1989, more than 18 years after start-up of the 350 SL. This SL series set an internal record that will probably never be broken: in the entire history of the company no other passenger car series has ever been produced over such a long period, with the exception of the G-Class. All told, in Sindelfingen 237,287 open-top cars were built, a number which impressively demonstrates the great popularity of the 107 series. Of the coupé a total of 62,888 units were built from 1971 to 1981.

The R 107 series in the press

In a first test of the Mercedes-Benz 350 SL “auto motor und sport”, Germany, No. 9/1971, wrote: “Good suspension comfort, definitely up to saloon standard, proves to be an essential feature of the 350 SL: at low and high speeds it absorbs big bumps well and takes small bumps in a way that they are never a disturbance even on very poor roads.”

In 1986, “Road & Track”, USA, No. 11/1986, compared the Mercedes-Benz 560 SL, which was in the last era of its production, with the Cadillac Allanté and summed up: “Legendary quality is Mercedes’ primary stock in trade. But brilliant performance and outstanding ABS braking have freshened [the vehicle] this year. Against these attributes, Cadillac brings better handling and greater luxury to bear while failing to match Mercedes’ performance and quality.”

“auto motor und sport”, Germany, No. 5/1986, reported: “In curves, too, the modified SL displays a behaviour that does not go well with the image one tends to have of the vehicle. With its precise power-assisted steering, extremely high possible transversal acceleration and now only reduced load change behaviour, the long-snouted, rather staid-looking car delivers precisely that which one would expect from a purebred Gran Turismo.“

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  Further developed safety body
  
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  Frame floor assembly with sheet metal of different thicknesses and a resulting carefully-defined crumple behaviour
  
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  Rugged roll-over protection: high-strength A-pillars and windscreen frame with bonded glass for greater stability
  
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  Special air ducting in doors ensures low soiling of side windows and exterior mirrors
  
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  Bosch K-Jetronic contactless transistorised ignition, hydraulic valve clearance compensation (1975)
  
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  First SL with exhaust gas catalytic converter (1985)
  

* Before March 1973 only for export to North America.

** Export model for North America, Japan, and Australia.

*** Number of units contained in the figures for the 450 SLC 5.0.

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  Numerous innovations, from the automatic roll-over bar to the integral seat
  
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  Debut of the twelve-cylinder engine in the SL model, R 129 series
  
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  Official AMG versions available for the first time
  

The SL face captured a permanent place in the Mercedes-Benz model hierarchy over the decades. The new SL re-interpreted the traditional basic shape of the grille: within the radiator grille, organically integrated into the bonnet, the Mercedes star was complemented by horizontal strips made of anodised aluminium. Chief designer Bruno Sacco had done an excellent job. The stylistically assured, no-frills lines of the slightly wedge-shaped body, the flared wheel arches for the wide-base tyres, the half-spoilers forward of the front wheels, its steeply raked windscreen, skilfully modelled rear end and the standard light-alloy wheels produce an exceedingly harmonious overall effect.

The aerodynamic fine touches, including underbody and airflow through the engine compartment, added up to a fuel-saving, speed-increasing c_d of 0.32 with the hardtop mounted. A c_d figure of 0.40 was measured for the open-top car with closed side windows.

“Car Design Award”

Hardly a year after its launch the SL was awarded the international “Car Design Award”. The SL was the top choice of an eleven-member jury of journalists from ten countries, assisted by a representative of the city of Turin and one from the Piedmont region. The jury stated as reason for the prize: “In the Mercedes-Benz 300 – 500 SL the ensemble of safety innovations, ... exemplary ergonomic solutions, and stringent adherence to the traditional design culture of the manufacturer's brand is convincing. The new SL embodies the most valuable elements of up-to-date industrial design, without losing the flair that distinguishes every sports cabriolet.”

High torsional stiffness

The prerequisite for the proper operation of the fully automatic folding soft top under all conditions is the extremely high torsional rigidity of the body. To reduce the vibration and torsion characteristics typical of open-top cars, additional diagonal struts are fitted in the particularly critical areas of the body. In the front end the front axle carrier is connected with the door sills by two specially-shaped struts. In the rear end two tubular struts between the door sills and the spare wheel recess serve the same function. Owing to these measures it was possible to improve the torsional rigidity by around 30 per cent over that of the previous model, achieving a saloon-like overall rigidity achieved.

This car set new standards in the area of safety, too. The results of Mercedes-Benz’s rigorous frontal and rear-impact crash tests for the open-top vehicle were sensational and a clear proof of the scrupulous precision with which the developers had worked. The resistance to side impact went far beyond what the law required and once again set trends for the sensible design of all details, for instance the overlapping of the doors with the sills, the cross-bracing beneath the seats, including the rigid sides of the transmission tunnel, or the high-strength steel tubes inside the A-pillars, which can withstand a roof impact. This two-shelled structure of the front roof frame in conjunction with the bonding of the windscreen to the body results in very great stability even if a one-sided load is applied to the roof frame.

An integral part of the safety concept is the automatic roll-over bar which was realised in the SL for the first time in an automobile and has the purpose of protecting the occupants’ survival space if the car should overturn. So as not to impair open-top driving pleasure with a permanently installed, rigid rollbar, a flexible solution was implemented by which the roll-over protection was only activated if needed. When not in use the safety bar, consisting of a U-shaped high-strength steel tube foam-padded with polyurethane, was stored in front of the soft-top compartment, closing off the rear compartment towards the back and forming a level surface with the top well lid. If a roll-over threatens, the sensor-controlled roll-over bar is electromagnetically triggered, raised into position by the force of pre-compressed springs within 0.3 seconds and secured by pawls. The high-strength centre pillars, connected over a large area with the rear longitudinal members, serve as basis for mounting and as support. In addition to automatic triggering in an emergency, the driver can raise and lower the bar slowly by means of a switch, with a hydraulic element carrying out the action.

The most advanced feature of the interior design were the integral seats of the SL, a technical masterpiece of design and an important part of the safety concept. The seat frame and backrest are made of various special magnesium alloys executed in thin-wall casting technique. They incorporate the three-point seat belt with belt tensioner, the belt height adjustment, coupled with the head restraint adjustment, and electric stepper motors for adjusting reach, height and tilt of the seat cushion and backrest. Another important feature is the automatic positive locking of the backrest. The resistance of the seat in a crash is many times higher than the forces that could possibly arise.

Twenty patents for solutions to various details went into this seat; its creator received the Paul Pietsch Prize and high prize money as acknowledgement of his pioneering work in 1989.

Fully automatic folding soft top

The newly designed electrohydraulic fabric top with which the SL is equipped as standard offers especially great operating convenience. Simply by operating a switch, within 30 seconds the soft top can be opened, folded and deposited in the narrow soft-top compartment, or taken out of the compartment and closed. Simultaneously, the side windows and the roll-over bar are lowered and then returned to their starting positions. Up and closed, the top is taut and smooth in all directions – after all, it would be highly undesirable for the vacuum caused above the roof by the car’s movement to cause the top to balloon, and perfect operation of the roll-over bar under the closed soft top must also remain guaranteed.

The energy to operate the soft top is provided by an electrically-driven hydraulic pump located in the spare wheel recess together with the oil reservoir. The microprocessor-controlled motions are monitored with the aid of 17 limit switches, and the hydraulic system has 15 pressure cylinders and eleven solenoid valves.

The exemplary solutions included the draught-stop. Unlike the electro-hydraulic soft top it was not viewed as a high-tech marvel, but its development also involved attention to complex details. The draught-stop consists of a framed, breathable screen which can be quickly attached to the roll-over bar and which, when raised, appreciably enhances ride comfort when the soft top is open by minimising wind noise and draught. With the draught-stop, leather jackets and caps for driver and front passenger are a thing of the past, as is tousled hair for the ladies. Even high speeds no longer cause draught problems, and open-top driving at low temperatures becomes a real show. Today the innovative draught-stop, for which the inventors hold four patents, is practically taken for granted in many convertibles around the world.

The standard hardtop was now made of aluminium, and despite larger windows weighed just 34 kilograms, about ten kilos less than the coupé roof of the previous model. As it was, consistent lightweight design and the extensive use of high-strength sheet steel had enabled the creation of a bodyshell weighing 405 kilograms, only 20 kilograms more than that of the previous model, despite substantial improvements in structural safety.

Electrically-operated windows and the electro-pneumatic central locking system, both standard equipment in all SL models, served comfort and convenience. The basic equipment of the 500 SL also included electric steering column adjustment for optimum adaptation of reach, height and tilt to the driver.

The suspension conformed in principle to the familiar suspension design of the Saloons of the 201 and 124 series. The new SL models thus had a coil-spring shock absorber independent front suspension with anti-dive control and wishbones, gas-filled shock absorbers and stabiliser, and a modified multi-link independent rear suspension with anti-squat and anti-dive control, coil springs, gas-filled shock absorbers and stabiliser. This guaranteed excellent handling characteristics. Many components were adapted to the altered installation conditions, stresses and loads in the SL; the axle geometry, too, was matched to the special demands on the driving characteristics and comfort.

As an optional extra a newly-developed auxiliary system was also available representing the most advanced suspension technology realisable at the time, combining three subsystems. The purpose of this level adjustment and regulation on front and rear axle was to maintain a constant vehicle level with the engine running. The automatic speed-dependent level adjustment function lowered or raised the vehicle level depending on the actual speed; for driving on poor roads the level could be increased by 30 millimetres; at a speed of more than 72 km/h the system adjusted to the normal level, and above a speed of 122 km/h the vehicle was lowered by 15 millimetres. The third component, the ADS Adaptive Damping System, used adjustable shock absorbers and a complex electronic control system to adapt the damping fully automatically, as needed, and within fractions of a second, to the driving state determined by five sensors. The overall sprung mass vibrations were reduced in accordance with vehicle load, road condition and style of driving. This was virtually a preliminary stage of the active suspension that reached production maturity in 1999 in the C 215-series Coupé.

In keeping with their sports credentials, all models of the R 129 series were fitted as standard with 15-hole light-alloy wheels (diameter: 40.64 centimetres) and wide-base tyres size 225/55 ZR 16. The larger wheels compared with the previous models permitted installing large brakes appropriate to the improved performance of the SL. New were the front fixed-calliper disc brakes featuring four pistons, two pairs with different diameters each. This design, used for the first time in a Mercedes-Benz passenger car, ensures even brake pad wear and better utilisation of the pad volume. The front and rear disc brakes are internally ventilated. The ABS Anti-lock Braking System was part of the standard configuration of all three models.

From September 1995 on the Electronic Stability Program ESP^® was available for the SL 500 as an optional extra. It was standard equipment for the SL 600. From December 1996 onwards the six-cylinder models could also be equipped with ESP^® if they were ordered with the electronically-controlled automatic transmission available from June 1996. Another world first in the interests of active safety also saw use at this time: the BAS Brake Assist, installed as standard from December 1996 in all models of the 129 and 140 series. BAS is able to detect emergency braking and, in case of need, automatically build up the maximum brake boosting effect more rapidly than before. This distinctly reduced the braking distance of the vehicle. In early April 1998, the Electronic Stability Program ESP^® was included as standard equipment of the SL 500 and SL 60 AMG; in August 1999 it also became a standard feature in the two six-cylinder models, SL 280 and SL 320.