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Back to the Future: the Mercedes-Benz 190 D BlueEFFICIENCY

September 8th, 2009
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From the outside it looks just like a 20-plus year-old Mercedes 190, tens of thousands of well-preserved examples of which can still be seen on Germany's roads.

Pressing the accelerator tells a different story: equipped with the ultra-modern OM651 common-rail engine developing 150 kW, the Mercedes 190 D BlueEFFICIENCY shows the full potential of this new four-cylinder diesel engine.

With a maximum torque of 500 Nm between 1600 and 1800 rpm, this experimental car has more than twice the torque of the most powerful model in the old W 201-series: the famous 190 E 2.5-16 Evolution II. This limited-volume homologation touring car racing special, "only" managed 245 Nm.

The idea for this unusual experimental vehicle came about during an evening discussion about the enormous developments in diesel technology over the last 20 years. The question was: "How might one make this progress directly tangible, in isolation from the equally profound changes in the safety and comfort of the car as a whole?"

The result was a factory-tuned car of a different kind: the 190 D BlueEFFICIENCY.

It accelerates from 0 to 100 km/h in 6.2 seconds. It therefore manages this standard sprint 11.9 seconds faster than a 190 D of the time, which caused a sensation on its 1983 introduction with its newly developed, fully encapsulated "whisper-diesel".

The differences between the two diesel generations are even more impressive when it comes to fuel consumption: despite the significant increase in output by 72 hp (OM 601, 1988) to 204 hp (OM651, 2009), the new engine in the old body consumes 4.9 litres per 100 kilometres (NEDC) instead of the 7.3 litre figure for 1988.

But what is really astonishing is that measured according to the DIN standard used during the time of the 190 D, the Euro-Mix consumption of the current C 250 CDI BlueEFFICIENCY is a mere 4.6 litres per 100 kilometres, and 5.1 litres per 100 kilometres according to the present NEDC method. This represents an improvement of around 30 percent - not to mention the exhaust emission levels.

The playing field is by no means level: a Mercedes 190 D is 385 kilograms lighter than a current C 250 CDI BlueEFFICIENCY, for example. In addition to more interior space - the current C-Class model is 16 centimetres longer, and around nine centimetres wider and higher than a 190 - this is due to the high standard of comfort and safety features.

The Mercedes model 190 was ahead of its time in terms of safety technology. Nonetheless, customers at the time enjoyed nothing like the extensive array of passive and active safety systems to be found as standard in the current C 250 CDI BlueEFFICIENCY. These include seven airbags, the adaptive AGILITY CONTROL suspension and numerous assistance systems such as ESP® and ADAPTIVE BRAKE. Comfort-enhancing features like the ergonomically exemplary, multi-adjustable seats or electrically adjustable and heated exterior mirrors also contribute to the higher weight.

A number of factors are responsible for the outstanding efficiency of the current C-Class. Aerodynamics is one of them: with a Cd figure of 0.34 the 190 set an example for its time. The new C-Class betters this figure by far, however, and is once again the trendsetter in this segment with a Cd figure of 0.27.

The progress is equally impressive where the powertrain is concerned: while the 190 D was equipped with a four- or optionally available five speed manual transmission, the C 250 CDI has a six-speed manual gearbox available. Plus, it employs a large number of friction-reducing measures. The radiator fan, power steering and generator also operate much more efficiently than 20 years ago.

Conversion work: Generations in conflict

"No, I can't say it was a real bargain", says Peter Lehmann, reflecting on his purchase of the 190 E 2.6 which provided the basis for the unusual conversion.

"After all, the W 201 has long since gained collector status, and this example dating from 1992 was in particularly good condition."

Lehmann knows a thing or two about the 190-series: as a Mercedes-Benz engineer responsible for the design and realisation of show cars and concept cars, and as the team leader for the conversion work, he privately owns no less than three 190s, ranging from the entry-level variant with its frugal 1.8-litre engine to the potent Evo model.

The small team that installed a new diesel power unit into the old 190 body within the space of a year also included two other, equally staunch fans of this model series. And they were not alone in their enthusiasm: "Almost every time the 190 was left in our workshop overnight, there was a note attached to it next morning asking if it was for sale", says Lehmann.

But it was not, and it has meanwhile become a priceless one-off example.

Packaging: what doesn't fit is made to fit

The 190 E 2.6 selected for the conversion work was a good choice: its six-cylinder power unit weighs around the same as the modern OM651, maintaining the weight balance between the front and rear axles.

Moreover, the braking system of this former 160 hp model was already robust enough to keep very many more, modern diesel horsepower in check. As a Sportline version, this 190 also possessed a sporty, taut suspension setup which could be left unchanged.

The usual day-to-day occupation of the conversion team was to look well into the automotive future with concept cars. This time, however, it was a matter of resolving the past.

The first challenge was that no CAD data existed for the 190. As used to be the practice, drawings of the engine compartment and engine were therefore transferred to see-through paper, then superimposed. As everything seemed to fit reasonably well, the body dimensions were accurately measured. The resulting figures were reconciled with the engine data to identify any potential collision points.

And packaging problems there certainly were. The steering would have passed straight through the sump, for example. A solution was found by consulting colleagues in the commercial vehicle sector: the sump of the Mercedes-Benz Sprinter was a good fit. The Sprinter is incidentally a distant relative, for the van is also available with the modern OM651 four-cylinder common-rail diesel engine.

The adaptation work, however, did not end there. The transmission tunnel of the 190 had to be widened to accommodate the current six-speed transmission, and in the case of the rear axle differential the team had recourse to the replacement parts range: the differential of the 3.2-litre W 203 (that is,  the predecessor to the current C-Class) proved suitable.

Electronics: if it does not exist, it is simulated

"The greatest challenge during this project was not in fact the hardware, but rather the electronics", says Peter Lehmann.

This because the 190 did not yet have a CAN-bus as a data transfer system. In the current C-Class with its state- of-the-art OM 651 engine, more than one dozen control units are in constant communication with each other to coordinate their respective tasks. The car will not start without the right signals, as the electronic ignition lock acts as a link between the engine CAN-bus and the interior CAN-bus.

So the team creating the 190 D BlueEFFICIENCY came up with a clever idea: they fooled the engine into thinking it was on a test bench. The appropriate signals are sent by a box of electronics roughly the size of two shoe-boxes in the boot. This is what enabled the OM651 to spring to life, and it performs its duties with the usual quietness and refinement under the bonnet of the W 201.

But the next problem was not long in coming: for the car to operate as it should, the electronics required ABS signals. Turning wheels cannot be duplicated even on a virtual test bench, however, so once again the electronics specialists were called for - and now the ABS signals are likewise simulated.

"The driving experience is really unique", Lehmann enthuses.

"The modern diesel is easily able to cope with the 190. This level of muscular torque was simply unimaginable at the time, likewise the amazingly low fuel consumption."

There were other things beyond the wildest dreams of the engineers developing the W 201 at the end of the '70s; for example the digital speedometer or four-channel ABS.

"With its uncluttered design, the 190 appears timeless and drives very well indeed. Nonetheless the technical progress made in automobile engineering over the last three decades was our constant companion during the conversion work", Lehmann concludes.

The new four-cylinder diesel engine generation: Leading the way in terms of power output, consumption and emissions

The basic character of the new four-cylinder diesel generation from Mercedes-Benz can be described in just a few superlatives: greater power, greater economy, and greater cleanliness.

The new power unit from the Untertürkheim plant needs to be explained at greater length to be fully appreciated. It really does charter territory from which diesel engines - and particularly four-cylinder units - have previously been excluded. It redefines standards for power output and torque on the one hand and for fuel consumption and exhaust emissions on the other, setting benchmark figures which no other comparable series-production engine is able to match at the current time.

The technical advances which the design engineers at Mercedes-Benz have achieved with this new four-cylinder diesel are not only evident on paper; its effects can also be experienced to an intense degree behind the wheel. As far as the figures are concerned, the most powerful variant of the new diesel engine extracts 150 kW from its displacement of 2143 cubic centimetres. The power-to-displacement and torque-to-displacement ratios of the new engine are just as impressive, with figures of 70 kW and 233.3 Nm per litre respectively.

Lower fuel consumption despite substantial gain in output

The engineers also took care to ensure that the new diesel engine is a paragon of fuel efficiency. Despite the substantial power boost of 25 kW, the engine makes even more frugal use of diesel than its predecessor, which was itself a most modest consumer of fuel. This is immediately apparent from the fuel consumption figures for the new C 250 CDI BlueEFFICIENCY. When fitted in the C-Class, the new 150-kW unit burns just 5.1 litres of diesel per 100 kilometres (NEDC), 0.8 litres less than previously. The Mercedes-Benz engineers have also succeeded in further reducing the untreated engine emissions. The new four-cylinder diesel already meets the future EU5 emission standard.

Innovative technologies without parallel

The exemplary figures achieved by the new engine for output and torque characteristics, economy, exhaust emissions and smoothness are the result of a whole raft of innovative technologies. The principal features of the new Mercedes diesel engine:

Diesel engines in Mercedes passenger cars: From the world's first diesel car to the C 250 CDI BlueEFFICIENCY

The diesel engine has been regarded as the epitome of durability for many decades: staunch and reliable of course, but also associated with a touch of sluggishness. "Brisk progress" was the term used to circumscribe this lack of dynamism in brochures from the 1970s.

Over time this characteristic has completely disappeared, making way for a totally new image. Sportiness, agility, ride comfort, driving pleasure and, not least, environmental compatibility are attributes to which modern diesel engines can nowadays lay claim. Engineers at Mercedes-Benz have been actively contributing to this progress for more than 70 years:


The model 260 D (W 138-series) was the world's first series-production diesel passenger car. The 2.6-litre engine had a compression ratio of 1:20.5 and delivered 33 kW at 3200 rpm.


With the model 170 D (W 136-series), Mercedes-Benz again included a four-cylinder car diesel engine in the model range. The 1.8-litre OM 636 L generated 28 kW at 3200 rpm.


The diesel models 180 D (W 120-series) and 190 D (W 121-series) appeared on the roads in the outfit of the 'Ponton' design presented in 1953.


In the "Tailfin" design (W 110-series) the diesel car emancipated itself even further from its commercial vehicle origins: the two-litre diesel introduced in 1961 was still called the 190 D, but when Mercedes-Benz presented the new model 200 in 1965, the diesel variant was also renamed the 200 D. Overall displacement and output (44 kW at 4200 rpm) remained unchanged.


In the W 115-series, two new diesel models were introduced together for the first time in 1968, the 200 D and the 220 D. In 1973 the 240 D was added to the range, to be followed in July 1974 by the top-of-the-line 240 D 3.0. This model was powered by the world's first five-cylinder car diesel engine. With an acceleration of 19.9 seconds from 0 to 100 km/h, the new diesel model was the fastest diesel car in the world.


At the 1977 International Motor Show (IAA), a further diesel model specifically designed by Mercedes-Benz for the American market attracted great attention: the 300 SD was the first S-Class (W 116-series) and the very first luxury class model anywhere to be equipped with a diesel engine. An appropriate performance for the luxury saloon was ensured by a turbocharger, which increased the output of the five-cylinder diesel to 85 kW.


In 1982 Daimler-Benz introduced the compact class as its third car model series. In 1983 the compact Mercedes known as the 190 D was given a new 2-litre diesel engine (53 kW at 4600 rpm). This unit was designed to be particularly light, economical and responsive. Above all though, the engine was fully encapsulated to reduce noise by one half.


For the first time in a Mercedes-Benz passenger car, the medium-class 124-series fielded a model with an in-line six-cylinder diesel engine: the 300 D (80 kW at 4600 rpm).


From autumn 1992 the S-Class (W 140-series) powered by a 3.5-litre turbodiesel also became available in Europe: the diesel engine had finally established itself internationally in the automotive luxury segment. This model delivered 110 kW, with a turbocharger and emission control system using an oxidising catalytic converter included in the standard equipment.


Four-valve technology was introduced by Mercedes-Benz as a world first. Using four instead of two valves per cylinder made it possible to achieve a higher torque and output over a considerably wider engine speed range, while also reducing fuel consumption under full load by up to eight percent.


The E 290 Turbodiesel in the E-Class with the new twin-headlamp face attracted great attention. For the first time in a Mercedes-Benz, its OM 602 DE 29 LA in-line five-cylinder engine offered a combination of diesel technology and direct injection.


In the C 220 CDI, Mercedes-Benz presented direct injection according to the new "Common Rail Direct Injection" (CDI) principle.


Easily the most powerful diesel engine in a Mercedes-Benz car was introduced into the S-Class in 2000. The light-alloy OM 628 DE 40 LA V8-engine generated 184 kW at 4000 rpm from a displacement of four litres.


As the first manufacturer in the world, the company introduced diesel cars complying with the Euro 4 standard, with a maintenance-free particulate filter.


The world's highest-torque V8 car diesel engine (OM 629) entered series production in the Mercedes-Benz E-Class in autumn 2005. This 231 kW V8 power unit already made a maximum torque of 730 Newton metres available at 2200 rpm.


Mercedes-Benz equipped all its diesel passenger cars from the A- to the S-Class with a diesel particulate filter as standard in Germany, Austria, the Netherlands and Switzerland.


Mercedes-Benz introduced the world's first diesel models with AdBlue injection in America (R 320 BlueTEC, ML 320 BlueTEC and GL 320 BlueTEC).


A new generation of four-cylinder diesel engines celebrated its debut in the C 250 CDI BlueEFFICIENCY. Features: two-stage turbocharging and fourth-generation common-rail technology with a rail pressure of 2000 bar, as well as a new piezo-electric injector design with direct nozzle needle control.


Model history of the C-Class: Innovation as a tradition

27 years ago, with the model 190, Mercedes-Benz laid the foundations for what is now its best-selling model series: the C-Class. To date, a total of around 6.6 million C-Class Saloons, Estates and Sports Coupés have been delivered to customers globally.

When the 190 was developed, the engineers were already subject to strict target specifications that are still valid today. They had to reconcile consumption-related criteria such as low weight and good aerodynamics with the high Mercedes standards governing occupant safety, handling stability, comfort and quality.

Innovations in diesel technology in particular have always had a decisive influence on the success story of the 190 and the C-Class. An overview of the model history:

"Refreshingly unconventional": the Mercedes 190 (1982 – 1993)

When Mercedes-Benz presented the model 190 in 1982, it was quickly nicknamed the "Baby-Benz". The Saloon (W 201-series) was the first in a new model series positioned below the E-, S- and SL-Class models, and known in-house as the "compact class". The designer responsible for its straight lines and distinct wedge-shape with subtle light-breaking edges was Bruno Sacco.

"A refreshingly unconventional, modern car which can be expected to capture the enthusiasm of new and especially young buyers", Neue Züricher Zeitung wrote on 22 December 1982.

The car also transferred other Mercedes values such as a passion for technical innovation to the mid-series. Accordingly the W 201 was given a multi-link independent rear suspension, a weight-saving construction using high-strength steels, an aerodynamically exemplary bodyshell and outstanding passive safety features.

The 190-series also set new standards where the engines were concerned: in the diesel sector with an encapsulated unit that soon earned itself the sobriquet "whisper-diesel" in the model 190 D (from 1983). This completely newly developed four-cylinder diesel engine with a displacement of 1997cc was half as noisy as comparable drive units. In conjunction with the then respectable output of 53 kW and good fuel economy, this made the new diesel an all-round, innovative success.

New name: the first C-Class (1993 – 2000)

The 202-series was the first to bear the name C-Class. The Saloon (W 202) was launched in 1993. The C-Class followed the tradition of the 190, but offered more interior space and comfort with similar exterior dimensions. At comparable prices, the standard appointments were also much more extensive. In 1996 the range was extended with the Estate (S 202), which offered exemplary spaciousness for this vehicle class.

The 202-series had a decisive effect on the further development of car diesel engines at Mercedes-Benz: it was in the C-Class that four-valve diesels for passenger cars first celebrated their world premiere. This was followed by the first turbodiesel car with four-valve technology and intercooling.

In 1997 the diesel engine with common-rail direct injection (CDI) celebrated its debut in the C-Class. "Its forte is refinement", the motoring magazine mot said of the Mercedes-Benz C 220 CDI in January 1998: "Common-rail separates the injection from the pressure stage, and the pre-injection made possible as a result compensates the ignition delay – which spells the end of noisy direct injection."

Three body variants: the second C-Class (2000 – 2007)

In March 2000, the second-generation C-Class looked out at the world through dynamically designed twin headlamps. Its attractive appearance provided a platform for a whole raft of technical innovations. This packaging characterised both the Saloon (W203) and the Estate presented in 2001, as well as the new Sports Coupé added to the C-Class family in the European Autumn of 2000.

Standard equipment included future-oriented technical innovations that had previously only been available in the top Mercedes models: windowbags, adaptive airbags for the driver and front passenger, Headlamp Assist, a multifunction steering wheel, a central display and optical fibres are just a few examples. The technical innovations that made their debut in this generation of the C-Class included the automated SEQUENTRONIC six-speed transmission.

More individuality: the third C-Class (since 2007)

Safety, comfort and agility were the outstanding attributes of the current C-Class launched in Europe on 31 March 2007 (Australia July 2007). This is the first Mercedes saloon in which the design and equipment lines have their own, distinctive front ends.

In addition to the driving refinement typical of a Mercedes, all model variants feature the latest technical highlights. These include, for example, the AGILITY CONTROL suspension package with situation-related damper control, the Intelligent Light System with five different lighting functions and the PRE-SAFE® preventive occupant protection system.

From Autumn 2008 a completely newly designed generation of diesel engines also became available for the Saloon (W 204) and the Estate (S 204), which introduced in September 2007. These used 4th-generation common-rail technology with a rail pressure of 2000 bar, as well as a new piezo-electric injection concept with direct nozzle needle control for more flexible injection timing, and therefore smoother running. The first model was the C 250 CDI BlueEFFICIENCY Prime Edition, which developed 150 kW and a torque of 500 Nm from a displacement of 2.2 litres. Despite its outstanding performance, the Prime Edition of this model consumes an average of only 5.2 litres of fuel (NEDC) per 100 kilometres (CO2 emissions: 138 g/km). This model is currently not sold in Australia.

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