Review: Mercedes R170 SLK 32 AMG (2001-04)

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• Powerful 3.2-litre M112 supercharged V6 engine
• Impressive ride/handling balance
• Supportive front seats
• High standard of interior fit and finish

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• Steering lacks precision
• Cramped interior

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Overview

Released in Australia in September 2001, the Mercedes-Benz R170 SLK 32 AMG was a two-seat convertible with a retractable hardtop. Manufactured in Bremen, Germany, the rear-wheel drive SLK 32 AMG was powered by a supercharged 3.2-litre V6 petrol engine that was mated to a five-speed automatic transmission – this powertrain was shared with the W203 C 32 AMG .

M112.960 supercharged V6 engine

Assembled by hand at the Mercedes-AMG plant in Affalterbach, Germany, the 3199 cc M112.960 V6 petrol engine had an alloy cylinder block with 89.9 mm bores and an 84.0 mm stroke, cast-in Silitec (Al-Si alloy) cylinder liners, forged steel connecting rods, iron-coated aluminium pistons, an alloy cylinder head, a single overhead camshaft (SOHC) per cylinder back driven by a double-roller chain, three valves per cylinder (two intake, one exhaust) actuated by roller rockers, a compression ratio of 9.0:1, two spark plugs per cylinder and Bosch ME 2.8.1 engine management.

The M112.960 engine was fitted with a twin-screw, belt-driven IHI supercharger. To minimise fuel consumption, the supercharger was activated by an electromagnetic coupling according to load and engine speed conditions. The supercharger featured Teflon-coated rotors – which could achieve 20,700 rpm at maximum engine speed – and provided peak boost pressure of 1.22 bar (17.7 psi). The water/charge-air cooler was mounted between the cylinder banks and connected to a separate radiator that was located at the front of the vehicle in the fresh air stream. While peak torque was 450 Nm at 4400 rpm, over 400 Nm was available from 2300 rpm.

Compared to the standard M112 engine, changes for the supercharged M112.960 engine included:

• A new crankshaft with bearings adapted to the high torque;
• New connecting rods;
• A temperature-resistant coating for the pistons to withstand peak pressures in excess of 90 bar;
• A new balancer shaft;
• A higher-volume oil pump for increase oil supply to the oil nozzles (which had a 70 per cent higher output);
• Lightweight, assembled camshafts;
• Harder valve springs to increase the rated engine speed (from 6000 rpm to 6220 rpm) and resulting valve forces;
• An air pressure sensor instead of the usual hot film air mass meter; and,
• A unique exhaust system with four ceramic catalytic converters.

The SLK 32 AMG could accelerate from rest to 100 km/h in 4.2 seconds and had an electronically-limited top speed of 250 km/h. Over the combined NEDC test cycle, fuel consumption was 11.2 litres per 100 km. [su_table responsive=”yes”]

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AMG Speedshift transmission

Compared to the regular five-speed automatic transmission in the R170 SLK-Class range, the AMG Speedshift transmission:

• Had a one-touch sequential shift function;
• Provided gearshifts that were up to 35 per cent faster;
• Had a torque converter lock-up function above first gear to reduce torque converter slip and increase fuel efficiency;
• Had a downshift braking function if deceleration conditions were satisfied;
• Would stay in the current gear if a certain level of lateral acceleration was present (intended to delay or prevent gearshifts when cornering); and,
• An optimum gear function – selected by moving the gearshift lever to the left – which would cause the transmission to select the gear for maximum acceleration (depending on current speed and engine management data).

Gear ratios for the AMG Speedshift transmission were 3.59 (1st), 2.19 (2nd), 1.41 (3rd), 1.00 (4th) and 0.83 (5th), while the final drive ratio was 3.07:1.

Dimensions and body

The Mercedes R170 SLK 32 AMG was 4010 mm long, 1712 mm wide, 1270 mm tall and had a 2400 mm long wheelbase; kerb weight was 1495 kg. When the power-operated retractable roof was raised, booth capacity was 348 litres; this decreased to 145 litres, however, when it folded into the boot.

Compared to the R170 SLK-Class , the SLK 32 AMG could be identified by its unique front and rear aprons, integrated front fog lights, side skirts, dual chrome exhaust pipes and an integrated ‘airflow breakaway edge’ on the bootlid which reduced rear axle by more than 50 per cent.

Suspension

The Mercedes SLK 32 AMG had double wishbone front suspension and multi-link independent rear suspension, both with coil springs, gas-pressure shock absorbers and torsion bar stabilisers. Compared to the R170 SLK-Class, suspension changes for the SLK 32 AMG included:

• New spring/damper configurations;
• A wider rear track (1477 mm); and,
• A thicker torsion bar for the front axle.

Steering

The Mercedes SLK 32 AMG had power-assisted, recirculating ball steering.

Safety equipment

Standard safety equipment for the Mercedes SLK 32 AMG included dual front airbags, front seat-mounted side airbags, ABS, brake assist, traction control (Mercedes-Benz’s ASR), electronic stability control and front seatbelts with pre-tensioners and load limiters.

Brakes: SLK 32 AMG

The Mercedes SLK 32 AMG had 334 mm by 32 mm front brake discs with twin-piston callipers and 300 mm by 22 mm rear discs with single-piston callipers; both front and rear discs were internally vented.

Euro NCAP crash testing

In Euro NCAP crash testing , a 2002 Mercedes-Benz R170 SLK 200 – fitted with dual front airbags and front side airbags – received a four star adult occupant protection rating with a score of 26.12. In the frontal impact, the airbag cushioned the driver though the driver’s head moved to the left and turned through 90 degrees – this was not helped by the movement of the steering wheel and seat. Furthermore, protection from serious chest and lower leg injury was marginal.

Features: Mercedes SLK 32 AMG

Standard features for the Mercedes SLK 32 AMG included 17-inch twin-spoke AMG light-alloy wheels (7.5J front and 8.5J rear) with 225/45 ZR17 front and 245/40 ZR17 rear tyres, a four speaker sound system with a CD player, dual-zone climate control air conditioning, cruise control (‘Speedtronic’), AMG sports seats with power adjustment and heating functions, two-tone leather upholstery, front fog lights, a leather-wrapped AMG steering wheel and gear knob, remote central locking, power mirrors, power windows, an anti-dazzle rear view mirror, dark bird’s eye maple wood trim for the centre console and an immobiliser.

Extra-cost options for the SLK 32 AMG included a Bose sound system and xenon headlights.

Related links

• Wikipedia.org: Mercedes-Benz R170 SLK-Class