The powertrain: Connect four

The new entry-level model is the SLC 180 with an output of 115 kW (156 hp). It has an NEDC consumption figure of just 5.6 l/100 km and CO2 emissions of 127 g/km. Positioned above this are the SLC 200 with an output of 135 kW (184 hp) and the SLC 300 with 180 kW (245 hp), both of which feature a 1991 ccfour-cylinder engine. The efficiency champion remains the 150 kW (204 hp) diesel model, the SLC 250 d, with a CO2 figure of 114 g/km.

The three four-cylinder petrol engines available for the new SLC belong to a family of modern engines bearing the internal designation M274. They all share the third-generation direct injection system with spray-guided combustion. The system pressure is up to 200 bar with the pressure being variably optimised in line with the engine mapping. Piezo injectors enable optimal mixture formation with up to five injections per power stroke.

This technology is supplemented with the rapid multi-spark ignition (MSI), which is able to trigger up to four sparks a millisecond as required. The interplay of the two technologies allows optimum fuel utilisation with minimal emissions. All engines in this model series also feature an exhaust gas turbocharger.

With the sports exhaust system the sound experience can be intensified as the acoustics can be adjusted via an integral exhaust flap in conjunction with the DYNAMIC SELECT transmission modes. The SLC 300 is fitted with the sports exhaust system as standard, while it is available for the SLC 200 in conjunction with 9G-TRONIC and the AMG Line/Sports package.

A diesel engine has been available in the Mercedes-Benz compact roadster since 2011. This four-cylinder unit with a displacement of 2143 cc has an output of 150 kW (204 hp) and offers torque of 500 Nm. Fitted as standard with the 9G‑TRONIC automatic transmission, the SLC diesel can accelerate from zero to 100 km/h in 6.6 seconds and has a top speed of 245 km/h. As the efficiency champion of the range, it offers fuel consumption of a mere 4.4 litres of diesel per 100 kilometres (NEDC combined), a figure that corresponds to CO2 emissions of 114 g/km.

The engine achieves its exemplary performance in terms of output and torque characteristics, efficiency and exhaust emissions, as well as the smooth ride that is particularly impressive for a diesel engine, through the use of innovative technologies such as fourth-generation common-rail technology with precise injection timing and two-stage turbocharging

The BlueTEC emission control system comprises an oxidation catalytic converter, a particulate filter, the AdBlue® injection system and an SCR catalytic converter. Emissions of nitrogen oxides (NOx) are dramatically reduced by the injection of the urea solution AdBlue® and Selective Catalytic Reduction (SCR).

The SLC 180 and SLC 200 are fitted with a 6-speed manual transmission. The sport/comfort-oriented 9G-TRONIC automatic transmission is available for these models as an option and fitted as standard in the SLC 250 d and SLC 300.

The new model line-up at a glance:

 

SLC 180

SLC 200

SLC 300

SLC 250 d

SLC 43

Number of cylinders/ arrangement

4/in-line

4/in-line

4/in-line

4/in-line

6/V

Displacement (cc)

1595

1991

1991

2143

2996

Rated output
(kW/hp at rpm)

115/156 at 5300

135/184 at 5500

180/245 at 5500

150/204 at 3800

270/367 at 5500-6000

Rated torque
(Nm at rpm)

250 at
1200-4000

300 at
1200-4000

370 at
1300-4000

500 at
1600-1800

520 at
2000-4200

NEDC consumption (l/100 km) urban/extra-urban/comb.

7.4/4.5/5.6
(7.3/4.7/5.6)

8.1/4.9/6.1
(7.5/4.7/5.7)

(7.5/4.7/5.8)

(5.2/3.9/4.4)

(10.7/6.2/7.8)

Combined CO2 emissions (g/km)

127 (128)

142 (133)

(134)

(114)

(178)

Efficiency class

B (B)

C (B)

(B)

(A)

(D)

Acceleration
0-100 km/h (s)

7.9 (8.1)

7.0 (6.9)

(5.8)

(6.6)

(4.7)

Top speed (km/h)

226 (223)

240 (237)

(250)

(245)

(250)

In brackets: figures for version with 9G-TRONIC.


New 9G-TRONIC nine-speed automatic transmission: comfort and efficiency

The 9G-TRONIC, being used in the SLC for the first time, is a highly efficient transmission. The broad ratio spread of 9.15 for gears one to nine allows a clearly perceptible reduction in engine speed and is a decisive factor behind the high level of energy efficiency and ride comfort. Shortened shift and response times ensure optimum spontaneity combined with exceptionally smooth gear changes. Particularly in manual mode and the S and S+ modes, the 9G-TRONIC responds with significantly more spontaneity than the previous transmission used, so enhancing driving pleasure.

The exceptional drive comfort of the new 9G-TRONIC comes courtesy of a comprehensive package of measures. These include a direct control system that enables short, barely perceptible gear changes. The combination of twin-turbine torsional damper and centrifugal pendulum technology in the torque converter ensures outstanding ease of shifting. Together with the extended gear ratio spread, higher speeds can now be driven at lower engine speeds for even greater comfort.

A further focus of development work was the issue of "compact lightweight construction". Despite two additional gears and a maximum transferable torque of as much as 1000 Nm, this transmission requires as little installation space as its predecessor and is, furthermore, lighter in weight. The two-piece housing design has been retained: the torque converter housing is made of lightweight aluminium, while the transmission housing with weight-optimised plastic oil pan is made of an even lighter magnesium alloy. Nine gears are implemented with a minimal number of planetary gear sets and shift elements: only four simple planetary gear sets and six shift elements are necessary. Three speed sensors monitor operation and provide the transmission control system with corresponding data for effective shifting. It is possible here for several gears to be jumped when accelerating or decelerating, should the driving conditions call for it.

To ensure the reliable and at the same time energy-efficient supply of long-lasting and shear-resistant, second-generation synthetic fuel economy engine oil, the new automatic transmission is equipped with two pumps. The considerably smaller mechanical main pump, featuring an off-axis design, is located next to the main shaft and is chain-driven and fed by a separate electric auxiliary pump. This design enables the flow of lubrication and coolant to be controlled actively on demand and also means that the 9G-TRONIC can benefit from a start/stop system. Thanks to the world's first direct control system in a planetary automatic transmission with nine gears, it has also been possible to significantly increase hydraulic efficiency within the transmission. The higher number of gears and the broader gear ratio spread help to increase drive comfort and allow a significant enhancement to be achieved in terms of converting engine power into traction.

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Mercedes-Benz SLC 300; four cylinder petrol engine, 180 kW (245 hp), 370 Nm
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Mercedes-Benz SLC;  4-cylinder diesel engine (OM651); 150 kW (204 hp)
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Mercedes-Benz SLC; 4-cylinder petrol engine, (M274); 180 kW (245 hp)
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