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Redefining Four-Cylinder Performance

Published: 03/26/2013 - by Michael Taylor, Correspondent
Tobias Moers is still not completely happy with the steering in the 2014 Mercedes-Benz CLA45 AMG. He likes it, especially given AMG's relative lack of experience with making front axles twist, but he just doesn't quite love it. At least, not yet.
The AMG development chief assures us that he will get it right as he throws the CLA45 AMG prototype through the Swabian hills. Every drive, even drives like this with us in the passenger seat, helps AMG's 270-strong development team get the CLA45 closer to where the boss wants it to be.
When it hits showrooms here in November, the CLA45's steering will be just as Mr. Moers wants it. As for the rest of the car, it already feels like it's all there.
A Well-Honed Prototype
This drive, a two-hour exercise over the well-pounded roads around Affalterbach, is officially AMG inviting us to be part of its late validation program. Unofficially, it's a confident AMG simply showing off ahead of the car's U.S. debut at the 2013 New York Auto Show.

By the time it arrives in the fall, the 2014 Mercedes-Benz CLA45 AMG will deliver 355 horsepower from its turbocharged, 2.0-liter four-cylinder. That should be enough for a 4.6-second sprint to 62 mph, thanks in part to its standard all-wheel-drive system.
Beneath its four-door sedan skin, it's effectively the same car as the A45 AMG hatch that will be sold in Europe, right down to its wheelbase and track widths. Even the spring and damper rates on the Sports suspension version are identical on the two cars.
To justify the AMG badge on what is, effectively A-Class Mercedes-Benz architecture, Mr. Moers' team has worked hard on four main areas: the CLA's suspension system, the engine, the all-wheel drive and, of course, the exhaust.
Forceful Four-Cylinder
Using up to 26.1 psi of turbo boost inside the 2.0-liter engine forced AMG to mass-produce parts from the low-volume world of racing. The CLA45 boasts a sand-cast engine block, forged steel crankshafts, sand-cast aluminium crankcases and spray-guided direct fuel injection. It uses piezo direct fuel injectors in the center of the combustion chamber that allow for multiple injections per stroke and backs that up with multispark plugs, too.

On the roads around AMG's head office, that engine feels tremendously strong and sounds surprisingly rich. There have been strong turbo-4s before, most notably in Mitsubishi Evo Lancer and Subaru WRX STI bodies, but the CLA45 has them comfortably covered in performance and sophistication, not to mention sound quality.
While it has real strength from below 2,500 rpm, there is a slight softness below 1,500 rpm, yet it never complains or stutters when it's left to labor at 1,000 rpm in 5th or 6th gear.
From around 1,800 rpm, the engine builds gradually until it erupts with power at around 2,300 rpm. Its strength from 2,300 rpm onward is crushing, and it's hard to imagine another four-cylinder that will run with its in-gear acceleration.
Makes All the Right Sounds
There is barely an unwanted tremor or vibration through the body. All we hear and feel is the aggression AMG has purposely left in. AMG says it reaches its peak power at 6,000 rpm, but the CLA45 engine whips through to its limiter at 6,700 rpm without much thought, though the tone changes from deeply muscular in the midrange to something more athletic at higher revs.

Even as quick as it is, the highlights (especially with the louder Sports exhaust fitted and the Sport mode on) are the pops and crackles at every shift from the seven-speed dual-clutch transmission and the burbles on every over-run or lift-off. It's the best reason to leave the CLA45 in its Sports mode, as the car's behavior in the default setting is very civilized and makes it almost subtle.
The seven-speed transmission is fast and smooth, and those crackles and pops just encourage you to change gear even when it's not strictly necessary. It's flange-mounted onto the engine block and delivers a Race Start function for maximum getaway speed along with fast shifts, rev-matched downshifts and three different driving modes.
Puts the Power Down
Nestled inside the transmission are the lead-in parts of the Haldex all-wheel-drive system. It means the 2014 Mercedes-Benz CLA45 is designed to run as a front-wheel drive most of the time, but it can send power to the rear when it's needed.

"The car can send 50 percent of the drive to the back diff if it needs to, and you vary the torque split with the ESP button. It's normally front-wheel drive with the AWD as a traction support system, but in Sport it moves more torque to the back," Mr. Moers said.
Almost the entire suspension has been replaced from the standard Mercedes-Benz CLA, with a couple of exceptions that AMG forced onto Benz's main layout when the A-Class was under development.
This prototype of the CLA45 carries the standard suspension setup (there will be a harder, Sports option), and it all feels ridiculously organized and civilized in spite of its performance potential.
This CLA45 feels as if it walks a superb line between comfort and agility, losing nothing on long corners or on rapid direction changes. It also takes the supple ride of the standard car and builds on it with more accurate damping that delivers comfort without losing midcorner poise.
A Tantalizing Preview
Even if we didn't get to take the wheel ourselves, it was apparent from the passenger seat that the CLA45 is a true AMG sedan. Sure, there's no rumble of a big-displacement V8, but the sheer power and refinement of the turbocharged four-cylinder made us quickly forget that aspect of it.

This car has all the power it needs, and its smaller engine should deliver mileage numbers that are more in line with other sedans of its size. AMG knows it can't build V8 bruisers forever, and this attempt at bridging the gap feels like an honest effort that will be received well.
AMG officials also told us that this CLA will be priced very aggressively. If that's the case, then the 2014 Mercedes-Benz CLA45 AMG could very well become AMG's best-selling vehicle ever, V8 or not.
Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.
Strange that these prototypes didn't have the sports suspension.

And here is more information about the Haldex - edmunds seems to be confident that the torque split is 50/50

"The car can send 50 percent of the drive to the back diff if it needs to, and you vary the torque split with the ESP button. It's normally front-wheel drive with the AWD as a traction support system, but in Sport it moves more torque to the back," Mr. Moers said.
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