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Mercedes-Benz SLK Roadster – A Home Run! SLK Model and Feature Changes Through the Years

By   /  November 13, 2012  /  2 Comments

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Mercedes-SLK300-photo

This is the SLK’s tenth Anniversary. The SLK was announced to the USA market on Sept. 7, 1997 as a 1998 model; it was available in Europe during 1997. SLK production during these 10 years has doubled the 280/300/350/380/420/450/500/560SL (107 Body) during its 19 years of production. The SLK’s compact styling, retractable hardtop and optional 185/190 H.P. supercharged (Roots type) engine were a major departure from the large SLs of the previous quarter century.

The SLK is a modern incarnation of the 1950s 190SL by returning to four cylinders and a 94-inch wheelbase. Massively successful even its first year, worldwide sales hit 55,000, over double the entire nine-year production of 190SLs! The SLK was named “North American Car of the Year” by CAR & DRIVER magazine for 1998. Only in the USA sale of the SL320 (6 cylinder) was ended when the SLK arrived to distance it from the senior SL.

Chronology of Features and Changes

1997/1998: First year features included a five-speed automatic transmission, ASR to control wheel spin, ABS brakes and front and side impact airbags. The five speed automatic defers to higher shifting points when it senses “spirited” driving. It also changes shifting points when climbing or descending.

Three engine variants were offered:

  1. normal
  2. supercharged (kompressor) 2.0 liter and
  3. the C230 sedan’s 2.3 liter engine with a supercharged — the later being the only engine for the USA and UK.

A supercharger was chosen over a turbo as peak torque begins sooner at 2,500 RPM, up to 4800. There is variable rate valve timing, electronically controlled oil pressure, antiknock (ping) control and an anti-theft engine disabler. The distributorless ignition features a dual firing coil for each cylinder. Rear axle ratio is 3.27:1.

In the summer of 1997 US production included cruise control, air conditioning, an adjustable steering column and brake-assist, which became standard for the UK also. A few early cars do not include these features. The rear window is glass w/defroster. 1998 also brought “BabySmart” to turn the passenger’s airbag off whenever light infants or a booster seat was belted in.

Larger tires are used at the rear of the supercharged model which increases neutral handling. 16” wheels were used from the beginning. Suspension design conformed to M-B proven wishbones in front and five-link at the rear. The exhaust system’s center and rear mufflers are stainless steel. Headlights are halogen with variable focus reflectors. Remote key codes change every time the key is used however a transponder built into the key also exchanges a code in an electromagnetic coil that surrounds the ignition lock as an added antitheft control.

Fog lamps, power side mirrors and tinted glass are standard. Ditto power windows, cruise control, a telescoping leather wrapped steering wheel plus climate control with dust/pollen filter and separate controls for driver and passenger. Initial weight of the 2.3 was just over 3,000 lbs. 0-60: 7.2 sec. Top speed: 140. EPA city/hwy: 22/30 In the USA there were only four options: heated seats, metallic paint, heated headlight washers and a choice of telephone/CD changer combinations. A four-year/50,000 mile warranty included tires and battery.

1999: The driver adaptive five-speed automatic transmission became a $900 option, and about 20% of the US customers were expected to select the five speed shift. M-B claimed identical performance for each. A new $3,990 AMG designed Sport Package included 17″ wheels, and rakishly styled side sills plus front and rear fascias.

2000: Two unique “designo” paint and upholstery options were added. The “Copper Edition” came with copper metallic paint and an interior finished with copper and two-tone charcoal leather. Steering wheel, shift knob, floor mats, center console and rollover bars also receive a copper and charcoal. The 2nd designo SLK is “Electric Green,” using charcoal leather and trim with light green. Other interior options are Oyster/Charcoal or Salsa/Charcoal combinations or a solid Charcoal version.
A stabilizer bar was added to the rear and they reinforced the front one. A 3.46:1 axle was added for the manual shift SLK. Gas tank grew from 12 to 14 gallons.

2001: A 3.2-liter V6 and a six-speed manual transmission arrived in 2000 as a 2001 model. Concurrently the unibody was reinforced and they thickened the sheet metal of the ellipsoid firewall. Impact absorbers were added to side members to support the wheels in an offset crash. Inner panels of the doors were reshaped and reinforced. A link between the rear side body and main structure was added to disperse rear impacts. Brakes were enlarged on the V6.

Tele Aid and EPS became standard for all Mercedes-Benz in the USA. Tele Air incorporates remote diagnosis, emergency door unlocking and theft alarm notification. Emergency and non-emergency buttons establish immediate voice contact with reception specialists who can dispatch local police or other services. GPS tracking pinpoints location automatically. This also tells authorities the location of stolen SLKs. The 3.46:1 axle was dropped in the USA.

2002: Enter the SLK32 AMG with a whopping 349 HP. (0-60 in 4.8 seconds) Three engine choices: 1) 192 HP four valve, supercharged 4 cylinder, 2) 215 HP V6 and 3) the AMG V6. The SLK32 AMG’s engine has twin spark plugs per cylinder for maximum combustion. A newly engineered five-gear “SpeedShift” boasts 35% quicker automatic shifts. The SLK32 AMG uses lower (numeric) transmission gears and a 3.07:1 rear axle for an electronically limited top-speed of 155 mph. The standard four and six cyl. engines retain supercharging. Tell Aid services were expanded.

The AMG super charger is the Lysholm-type (screw type) which provides boost virtually from idle speed. The AMG variant has reinforced suspension and newly designed wheels for better brake cooling. Brakes became 13.15″ diameter vs. 11.8″ standard. Revised air dams/spoilers minimize and balance aerodynamic lift front-to-rear and top speed. A small lip spoiler at the trailing edge of the trunk lid reduces rear airlift by more than 50%. AMG interiors introduce more bolstered seats, unique two-tone leather and dark birds-eye maple wood. AMG instruments are finished in silver. The warranty included free adjustments and regularly scheduled maintenance for the full four years or 50,000 miles.

2003: No major changes or new features.

2004: Beginning in July 2004 a Special Edition was available with highly polished, win spoke 17″ wheels and high performance tires, newly designed sport seats and roll bars covered with Nappa leather.

2005: New Body -longer -wider -higher! New engines!

1997/2004

SLK350 SLK55
Wheelbase

94.5″

95.7″

95.7″

Length

157.9″

160.7″

160.9″

Width

67.5″

70.4″

70.6″

Height

50.4″

51.1″

50.0″

Cabin cu. ft

43.8′

48.8′

48.8′

Trunk cu. ft. (top up)

9.5′

9.8′

9.8′

Trunk cu. ft. (top dwn)

3.6′

6.5′

6.5′

Fuel Tank (gallons)

15.8

18.5

18.5

Four cylinder engines dropped from US choices. New V6 dropped supercharger and grew from a 3.2 liter, single overhead cam with 3 valves to 3.5 liters with double overhead cams and 4 valves per cylinder. Both V6 & V8 have two-stage variable intake manifolds. SLK350: 229 HP 2,400-5,000 RPM, up from 229 HP @ 3,000 to 4,000. 0-60 is down to 5.5 sec. MPG is down approximately 5%.

A 19% increase in the bending strength of the new body and 46% increased torsional strength with the top down allowed SLK’s first V8, AMG’s famous 5.5 liter in 355 H.P form coupled with an AMG tuned 7-speed automatic. The V8 is shod with 18″ wheels and larger, cross-drilled 6-piston fixed caliper brakes. All previous systems such as ESP (yaw control), ASR (throttle intervention for wheel-spin) are continued. Styling incorporates an arrow-shaped nose and long hood inspired from Formula One cars.

A revised retractable hardtop goes down more quickly (22 seconds) and takes up 31% less trunk space –thanks to its newly pivoting rear window. The entire body shell is zinc coated for long-term corrosion protection and they start using a more scratch-resistant clear-coat paint originally developed in the nanotechnology sector. It contains ceramic particles less than one millionth of a millimeter in size as part of the bonding agent. As the paint dries, these particles form a regular, dense pattern that triples the scratch resistance.Tests show a 40% improvement in gloss retention.

Another 2005 innovation is “Airscarf,” which is a neck level heating system that blows warm air from the head restraints, extending the open air season into cooler months. Airscarf automatically changes air temperature based on vehicle speed. MBUSA dropped free maintenance during the 4-year/50,000 mile warranty.

2006: To keep one SLK near the original 1997 launch pricing an 280 (actually 3.0 liter) liter V6 is added to the previous two engine choices. New owners enjoy faster acceleration and top speed than the previous 3.2 liter V6 thanks to sharing the 350’s variable twin cam 4 valve, 1 plug per cylinder design and 6 and 7-speed transmissions. The new engines, including the V8, are redlined at 6,500/6,700 RPM. Even the “budget” 280 engine earns a 155 MPH speed limiter and finds 60 MPH in 6.1 sec.

2007: HP increases to 228 and 268 respectively, on the 280 and 350 V6. These engines achieve 80% of maximum torque at a low-polluting, quiet 1,500 RPM. The engine includes unique tumble flaps that increase gas mileage by making extra turbulence at intake passages at part throttle.18/20 MPG can be expected in town and 25/27 in steady highway cruising.

Best Buy
Our list of significant equipment and models changes is reflected in the real world pricing chart shown on page 2 of the newsletter. Residual values for the SLK have always been among the best in the USA, especially for limited editions and AMG blessed models. The SLK has not experienced the black cloud some other M-B models have earned. If we add the conventional wisdom that depreciation slows as cars get older, our hypothetical “best buy” would be the oldest well preserved AMG model you are brave enough to buy: assuming the goal of ownership is getting most performance for the least future loss in value. If neck-wrenching performance is not required forget the AMG requirement.

Don’t rely on a seller’s candor. They’ve got a job to do… sell their car! Perfectly honest sellers may not even know the true condition of the undercarriage or if there is a leaky head gasket. Yet, one out of five SLKs are underutilized and meticulously serviced. That’s the one you want. It will cost a little more but you’ll feel like you bought a new car.

By John Olson – Editor & Publisher: The SL Market Letter

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2 Comments

  1. John W Byrne says:

    How many SLK’s were built in 2004 320’s & 230’s? How many Special Edition’s were made in both Models 320’s and 230’s?

    Thanks

    John W Byrne

    • John Olson says:

      Sorry for the slow reply; as fate would have it you’ve asked about the last year that Mercedes-Benz released this information on cars still in production, and the USA figures were reported in the SL Market Letter: 2004 SLK 230: 1,436. 2004 SLK 320 V6: 1,109. 2004 SLK 32 AMG: 190. 2004 SLK 55 AMG: 248.
      There has been a “black-out” of detailed production qualities since 2005 so we know a total of 11,278 SLK were sold through USA MNB dealers in 2005, but we don’t know how many were AMG variants, etc. I’ve dicussed this with the Mercedes-Benz Museum Archives management as car collectors place increasing importance on production quanities as cars get older. Explanation: Daimler’s corporate legal department imposed the restriction. There may be light-in-the-tunnel as total quanities of some models have been released after production concluded. Let’s hope that continues!