2011 Mercedes-Benz CL550: Dyno Tested


2011 Mercedes-Benz CL550

Think the CL-Class is a stuffy, stodgy isolation chamber for affluent quinquagenarians? Once you lay into the throttle, fuhgeddaboudit. There's a new kind of invigoration under the long hood of the 2011 Mercedes-Benz CL550. The kind of grunt that rivals -- nay, surpasses -- yesteryear's AMG-fettled models.

This, of course, is a prelude to another tale from the dyno.

2011 Mercedes-Benz CL550

Truly "all-new" engines are few and far between, and it's easy to guess why. The cost to develop and produce an engine approaches the GDP of a small nation. And really, an engine's newness is a moot point to most customers outside of enthusiast forums and conversations with the Joneses.

The 2011 Mercedes-Benz CL550's engine, called M278, is essentially all-new. It shares its basic architecture -- bore spacing, bottom end bearing package -- with the normally aspirated M273 that came before it. However, that's about all that remains, as it's been heavily reworked with direct injection, turbos and intercoolers, new subsystems and accessories, plus that all-important bigger last digit.

This upshot of all this downsizing and boosting is to decrease fuel consumption without giving up any performance.

What matters to the end user is the latter bit, and the M278 twin-turbo 4.7-liter V8 is pegged by Benz to chew out 429 hp at 5250 rpm and fully 516 lb-ft from 1800-3500 rpm. The outgoing aspro 5.5-liter M273? 382 hp and 391 lb-ft.

Interest adequately piqued, we took the 2011 CL550 to the dyno. Our test car was a 4Matic all wheel-drive model which required, appropriately, an all wheel-drive dyno. In this case we used a Mustang dyno. As such, comparisons to our usual Dynojet dyno are ill-advised.

2011 Mercedes-Benz CL550

The torque rolls over immediately after reaching its peak at 2900 rpm, a characteristic which is at odds with the plateau ending at 3500 rpm as described by the manufacturer. [Note: the sharp ramp prior to peak torque is in part due to the dyno operator rolling into the throttle while logging the data, so don't read too much into that portion.]

Torque ramps off at a constant rate all the way to the fuel cut, so the character of the engine is not one that craves revs (the falling torque curve is vaguely reminiscent of commercial diesel trucks, what with 'torque backup' and all). This is, after all, an engine powering a luxury car. You want your luxury cars quiet, too, and again the M278 complies, emitting barely a whine and a whoosh.   

2011 Mercedes-Benz CL550

At the wheels, we measured 357 hp and 461 lb-ft, but without a frame of reference, these are just numbers. We need a yardstick. Well, we've tested a handful of cars on this dyno, and one such car was the 2012 Nissan GT-R. Certainly these two cars have no commonality whatsoever and should never under any circumstances be compared for any reason. So let's see how they stack up:

You need look no further than the torque curves to discern the types of cars for which each engine is intended. Any self-respecting buyer of a modern $100k+ coupe wants effortless thrust. In other words, they want torque, at the low end, and lots of it, right now. The trend observed for the CL550's bent-eight is that there are indeed oodles of torque available down low, much more than in the Japanese supercar. Now if I could just figure out what an oodle is.

Yardstock-wise, our dyno operator reckons both cars are on the money vis a vis their claimed output. 

2011 Mercedes-Benz CL550

And sure enough the GT-R is better able than the CL550 to maintain its breathing in the upper reaches of the rev range, making it worthwhile to hang that sucker out. Just as sports car owners are wont to do.  

If the CL550's M278 is the harbinger of the new green, downsized and boosted movement, I say bring it on. There's so much torque on tap that tires everywhere are already cringing in fear, and this isn't even the uber-stout 5.5-liter version. Equally notable is the instantaneous way in which it's delivered -- most CL550 drivers won't even realize it's turbocharged, such is its seamless doling of marinade.

2011 Mercedes-Benz CL550

2011 Mercedes-Benz CL550

2011 Mercedes-Benz CL550

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