Track Tested: 2013 Mercedes-Benz SL550 vs 2012 BMW 650i Convertible


SL vs 650.jpg

The 2013 Mercedes-Benz SL550 is the newest player in the premium sport convertible segment, and with a base price of over $100,000 and an all-new 429-horsepower twin-turbo V8, it ticks those boxes handily.

But it's not alone in the segment.

BMW also has a twin-turbo V8-powered luxury sport convertible in the form of the 2012 BMW 650i. It has more seats and costs less, but the 4.4-liter V8 in the BMW only makes 400 horsepower and 450 pound-feet of torque. It's also backed by an eight-speed automatic, while the SL makes do with only seven forward gears.

With more power and less weight, the 2013 SL550 is expected to walk the BMW in performance testing, but is it enough to justify the price and lack of rear seats? Check the numbers after the jump and make the decision for yourself.

  2013 Mercedes-Benz SL550 2012 BMW 650i
0-30 (sec.): 1.9 2.1
0-45 (sec.): 3.0 3.4
0-60 (sec.): 4.4 5.0
0-60 with 1-ft Rollout (sec.): 4.1 4.7
0-75 (sec.): 6.2 6.8
1/4-mile (sec @ mph): 12.5 @ 113.2 13.0 @ 109.0
30-0 (ft): 29 29
60-0 (ft): 114 117
Skid pad lateral accel (g): 0.94 0.89
Slalom: 66.7 64.9
Top Operation Time (sec. down/up): 15.1/19.5 19.2/26.5

mb_sl_eng_1600.jpg

Vehicle: 2013 Mercedes-Benz SL550

Odometer: 1,544
Date: 4/24/2012
Driver: Chris Walton
Price: $124,460 (as tested)

Specifications:
Drive Type: Front engine, rear-wheel drive
Transmission Type: Seven-speed automatic
Engine Type: Twin-turbocharged, direct-injected V8, gasoline with auto-stop/start
Displacement (cc/cu-in): 4,663/285
Redline (rpm): 6,350
Horsepower (hp @ rpm): 429 @ 5,250
Torque (lb-ft @ rpm): 516 @ 1,800
Brake Type (front): 14.2-inch ventilated cross-drilled discs with 4-piston fixed calipers
Brake Type (rear): 12.6-inch ventilated steel discs with single-piston sliding calipers
Suspension Type (front): Independent multilink, pneumatic springs, self-adjusting 2-mode variable dampers
Suspension Type (rear):Independent multilink, pneumatic springs, driver-adjustable 2-mode variable dampers
Tire Size (front): 255/35R19 (96)
Tire Size (rear): 285/30R19 (98Y)
Tire Brand: Continental
Tire Model: ContiSportContact SP SSR
Tire Type: Asymmetrical, summer performance
As tested Curb Weight (lb): 4,130

Test Results:

Acceleration
0-30 (sec): 1.9 (2.0 w/ TC on)
0-45 (sec): 3.0 (3.1 w/ TC on)
0-60 (sec): 4.4 (4.5 w/ TC on)
0-60 with 1-ft Rollout (sec): 4.1 (4.2 w/ TC on)
0-75 (sec): 6.2 (6.3 w/ TC on)
1/4-Mile (sec @ mph): 12.5 @ 113.2 ( 12.6 @ 113.1 w/ TC on)

Braking:
30-0 (ft): 29
60-0 (ft): 114

Handling
Slalom (mph): 66.7 ( 65.9 w/TC on)
Skid Pad Lateral acceleration (g): 0.94 ( 0.93 w/TC on)

Db @ Idle: 44.3
Db @ Full Throttle: 74.5
Db @ 70 mph Cruise: 60.3

Db @ 70 mph w/top down: 71.5

Comments:

Acceleration: "Eco" mode disabled (so the engine is running), the default traction control is exceptionally good -- allowing a teeny bit of wheelspin. I barely "beat" it with my own, non-wheelspin launch. There's obviously enough torque to light the tires, but this only makes it slower. Power feels linear despite turbocharging. This engine reminds me very much of the "old" AMG 6.2 with its pull all the way up to redline. Upshifts are blazingly fast and smooth, as are matched-rev downshifts. Wow. (Still auto-upshifts in Manual mode).

Braking: Short and consistent distances. Every stop was absolutely fade-free (feel + distance) and dead straight, with no drama whatsoever. Felt like it would do the same stop all day long. ABC kept the car flat.

Handling:

Skid pad: With ESC off, the SL feels quite "free," requiring a lot of attention through throttle and steering to maintain a consistent arc. Steering, however, doesn't offer much feel or building effort, but is friction-free and precise. With ESC On, the throttle is subtly, almost imperceptibly manipulated and possibly brakes as well. I was "less busy" and the results were slightly better.

Slalom: Good initial steering response, but then by the second cone, the SL feels a half step behind with its ABC, and ESC is not truly off. Also, the unintuitive lack of suspension load and resulting body roll is further disconcerting. Best run was to cause the least amount of upset with the minimum amount of steering input, instead favoring the throttle to affect yaw. With ESC on, the differences were so slight (and perhaps non-existent) and boiled down to heated tires(?) or a reluctant throttle at the exit cone.

bmw650_eng_1600.jpg

Vehicle: 2012 BMW 650i
Odometer: 7,262
Date: 04/24/2012
Driver: Chris Walton
Price: $101,375 (as tested)

Specifications:

Drive Type: Front engine, rear-wheel drive
Transmission Type: Eight-speed automatic with console and paddle shifters
Engine Type: Twin-turbocharged direct-injected V8, gasoline
Displacement (cc/cu-in):4,395/268
Redline (rpm): 7,000
Horsepower (hp @ rpm): 400 @ 5,500
Torque (lb-ft @ rpm): 450 @ 1,750
Brake Type (front): 13.7-inch ventilated steel discs, single-piston sliding caliper
Brake Type (rear): 13.6-inch ventilated steel discs, single-piston sliding caliper
Steering System: Elecrtic speed-proportional power steering
Suspension Type (front):Independent multilink, coil springs, self-adjusting variable dampers, lower control arms, self-adjusting, active, stabilizer bar
Suspension Type (rear): Independent multilink, coil springs, self-adjusting variable dampers, self-adjusting, active, stabilizer bar
Tire Size (front): 245/35R20 (95Y)
Tire Size (rear): 275/30R20 (97Y)
Tire Brand: Dunlop
Tire Model: SP Sport Maxx GT DSST
Tire Type: Asymmetrical summer performance
As Tested Curb Weight (lb): 4,547

Test Results:
0-30 (sec): 2.1 (2.7 w/ TC on)
0-45 (sec): 3.4 (4.1 w/ TC on)
0-60 (sec): 5.0 (5.7 w/ TC on)
0-60 with 1-ft Rollout (sec): 4.7 (5.3 w/ TC on)
0-75 (sec): 6.8 (7.6 w/ TC on)
1/4 Mile (sec @ mph): 13.0 @ 109.0 (13.6 @ 108.1 w/ TC on)

30-0 (ft): 29
60-0 (ft): 117

Slalom (mph): 64.9 (64.2 w/TC off)
Skid Pad Lateral Acceleration (g): 0.89 (0.88 w/ TC on)

Db @ Idle: 52
Db @ Full Throttle: 67.4
Db @ 70 mph Cruise: 66.5
Db @ 70 mph w/top down: 69.3

Acceleration The default mode (Normal/Drive) hesitates slightly from a dead stop. Each successive mode makes the car slightly quicker (Sport, Sport+ and DS and manual). Once underway, the power comes quickly (perhaps due to gearing) and seems to carry all the way to the 7K(?!) redline. I "beat" traction control with a two-footed non-wheelspin launch with Trac off. Upshifts are both fast and smooth, as are matched-rev downshifts. (Still auto-upshifts in Manual mode).

Braking Comments: Only after realizing this car weighs 4,500 pounds did 117 feet from 60 feel appropriate (grew to 120). Mild distance fade and susceptible to surface conditions/undulations. The car remains flat and arrow-straight, however.

Handling Comments:

Slalom: With ESC off (in Sport), slightly delayed initial steering response, and the car grows increasingly tail-happy, especially off-throttle. Going in with maintenance throttle or trying to catch each slide, I always felt like I was a step behind. It requires a slow-in/fast-out technique to maintain rear bias and grip throughout. The active suspension is disconcerting and doesn't offer expected seat-of-the-pants feedback. With ESC on (in Sport+), I could be less concerned with the loose rear end and focus on car placement. Also, it was simple to whack the throttle to the mat and let traction control take care of things.

Skid pad: With ESC off (in Sport), the 650 feels well-balanced between under/oversteer. It's easy to hold to the line. Steering, however, is rather numb and the throttle response is a little lazy to use as yaw controller. With ESC on (in Sport+), I couldn't detect any intrusion at all, hence the near-identical numbers.

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