In the beginning, there was Eldo versus Mark III and IV, a recurring battle of personal luxobarges referred to as "King of the Hill" by Motor Trend in the 1970s. As the years went by, Lincoln departed Ford's Premier Automotive Group, and General Motors announced its intention to remake Cadillac the "standard of the world." Other European brands have more sporting intentions, but none owns the fast German autobahns more than Mercedes's torque-rich AMG machines, the CLS55 being one of its newest--and sexiest. Its AMG-built 5.4-liter V-8 mit kompressor is good for 469 horsepower and a pavement-pounding 516 pound-feet of torque that pushes 4307 pounds of steel, aluminum, plastic, leather, and suede.

But Cadillac is fighting back with its own 469 horses, complements of its new GM Performance Division-engineered Northstar V-8 SC, in one of its most powerful American production cars ever. The blown 4.4-liter makes 439 pound-feet at 3800 rpm in an upright, full four-door sedan. Before you reach for a pen or Blackberry, know we tried to get an E55 AMG to rub against the Caddy, as it more resembles the STS-v in terms of roofline and price. But Mercedes couldn't come up with one during our test window and offered this instead. The mechanicals are the same; simply adjust the base MSRP downward by about five grand for the E55.



Seventy mph is legal on most Michigan Interstates, and it's a quick shot through Northern Indiana and Chicago to Milwaukee, although the last two will seriously slow you down. Milwaukee has a large German-American population, a history of brewing beer, and a cool, avant-garde architecture art museum for photography. So we took I-94.




The flog began at a German-sounding American course, the "Lutzring" (a track at GM's Proving Grounds) for a test of each car's handling abilities. At this venue, neither exhibits super quick or communicative steering, but both handle more like sport sedans than full-size luxury cars. On public roads, the CLS55's heavy steering and wide AMG tires become a deficit at low speeds. At parking-lot pace, it feels like non-assisted steering. On the track, the Mercedes's five-speed automatic gets confused, not always knowing whether to downshift or upshift when you toe in and back out of the throttle.


The Caddy features the first application of GM's smooth new six-speed automatic, which serves the STS-v well at the Lutzring, whether you tap the gearshift up and down or let its sport mode pick the right gear, usually second or third here. The STS-v is biased toward understeer, while the Cad's attitude is neutral around the 'ring. It doesn't rotate until it's too late and then oversteer whips the tail. The Benz lets you steer with the throttle, progressively wagging its tail out.

Things change when reengaging traction and stability controls and taking to public roads. Cadillac's StabiliTrak will fishtail the STS-v out of power-on turns, while the Benz's electronic stability program gets jiggy on the throttle and ABS, holding momentum on a tighter leash. Once grip reestablishes itself, the CLS55 becomes a runaway freight train, able to thrust itself past mere mortal V-8s as if they were stuck in neutral.

Cadillac's powerhouse is nearly as impressive, but the torque deficit is obvious through the seat of your pants. After hitting 105.7 mph in the quarter mile, the Caddy struggles to reach 140 mph on our track, while the Merc does 114.5 mph and continues on to 140 as if it's a day in the park. You won't legally, sanely drive that fast, but Cadillac will sell the STS-v in Europe in minute numbers (North American volume will be about 2000 per year) as an image builder. On the real autobahn, quick spurts to 250 kph (about 140 mph) aren't uncommon, so this matters. Braking and lateral grip figures reveal the cars to be equally matched.




Both have fine, stitched-leather instrument panels. GMPD contracted Drexel Meyer, which also does Maybach's leather, to handle the leather and suede hides on the STS-v's dash, seats, and door panels. And it has heated rear seats, while the Benz has them only up front. But the Cadillac driver seat isn't as comfortable for long hauls, especially compared with the Mercedes's well-bolstered perforated leather and suede front seats. The v treatment is added to an STS interior, but falls short of its luxury intentions. This (admittedly good) patch job can't match an interior designed richly from the carpeting up, especially now that Mercedes is rebounding on interior quality.




Among the CLS55's many interior tricks is its dynamic driver's seat, in which the bolsters hold you in turns at the press of a button. Turn left, and the right bolster pumps up, and vice versa. It seems overwrought when gently changing lanes, but it's good on tight turns.



Standard nav systems, monthly-fee satellite radio, and cruise control help eat up a 785-mile round-trip. Neither navigation system is easy to use, sometimes providing incorrect information (note to Cadillac: Milwaukee has more than four hotels). And Cadillac's GM cruise control doesn't have a cancel switch. Mercedes's nav system (which doesn't have a "lawyer" screen you must acknowledge before using it) is better, but only by virtue of not being as confusing or confused as the Cadillac's. Mercedes's Sirius sat radio and Cadillac's XM have good selections of clear, digital sound.


For buyers of either car, the quality of the leather and the nav systems will go far in determining which automaker gets the monthly payment. By this standard, the Mercedes CLS55 would nab the old "King of the Hill" title. V-Series upgrades make the Cadillac a contender in this field, but they're like a baked-on layer of quality material, while the Benz's level of quality is deep fried to the bone.

To the issue of which owns the autobahn, American or otherwise, the STS-v does such an honest job that one no longer needs to ask whether Cadillac deserves to play in this universe. The STS-v appears the better buy, but with a major caveat. Cadillac is new to this price territory: Can it play at $75K plus, and is it likely to hold its value as well as BMW and Mercedes-Benz models do? If not, then its up-front price advantage will dwindle.



Which is king of the autobahn? The CLS55's outstanding performance, superb high-speed stability, and impressive cabin make the difference, even for a few dollars more. That Cadillac's entry is a credible large luxury/ performance sport sedan makes it a winner in its own right. Well done, but the Mercedes still gets the crown.

Supercharging The Northstar
By Frank Markus

Behold Cadillac's first production supercharged engine. Its official SAE-certified horsepower rating of 469 is the highest for any factory Cadillac, including all the jumbo-block SAE-gross-rated behemoths of the 1960s and early 1970s. Making power is all about getting air into cylinders. This can be done the Corvette Z06 way, using great big lungs, or by forcing air in with a blower. Cadillac reckoned the latter approach had a better chance of delivering the refinement and smooth idle demanded of a $77,090 car.

Air enters through an 80mm throttle body, flows around back of the engine and into the valley, where it's sucked up into the largest production Roots blower going. Spinning at 2.1 times crank speed, the air is pressurized to 12 psi before flowing up through a Laminova intercooler (water runs through tubes lined with closely spaced fins). The cooling fins drop pressure to 10 psi and quell the blower pulses. Air then U-turns and flows straight down into the intake valves to meet its octane-fueled destiny. Intake and exhaust valve timing are variable. Spent exhaust gases exit via extrude-honed ports, through cast manifolds and out through oversize catalysts and twin 2.5-inch sewer pipes.



The 469 horses arrive at 6400 rpm, but at least 395 of the 439 peak pound-feet of torque are available between 2200 and 6000 rpm. Fuel economy trails the naturally aspirated STS by three mpg city, six highway. And the idle quality is better, thanks to the added rotational inertia. There's way more to this Northstar than just a bolt-on blower, though.




Here are the highlights
1. The aluminum block is sand cast instead of die cast, necessitating 2mm smaller bore for better fatigue life.
2. Block and head castings undergo special T7 heat treatment and stabilization for strength.
3. Intake valve seats are copper infiltrated for better heat dissipation and wear.
4. Head gaskets reinforced to withstand 9:1 compression plus 10 psi boost.
5. Bigger oil jets cool the pistons with three gallons of oil per minute.
6. Oil pump, filter are higher capacity.
7. Two mufflers quiet intake roar upstream of supercharger.
8. Starter lives below blower in the valley for improved life (no road splash).
9. Low-restriction domino-shaped mass-airflow sensor replaces screen type (not shown).
* Note: XLR-v engine shown





2006 Cadillac STS-v 2006 Mercedes-Benz CLS55 AMG
Powertrain/Chassis
Drivetrain layout Front engine, RWD Front engine, RWD
Engine type Supercharged 90* V-8, aluminum block/heads Supercharged 90* V-8, aluminum block/heads
Valvetrain DOHC, 4 valves/cyl SOHC, 3 valves/cyl
Displacement 266.7 cu in / 4371cc 331.9 cu in / 5439cc
Compression ratio 9.0:1 9.0:1
Redline 6600 rpm 6500 rpm
Power (SAE net) 469 hp @ 6400 rpm* 469 hp @ 6100 rpm
Torque (SAE net) 439 lb-ft @ 3800 rpm* 516 lb-ft @ 2650 rpm
Weight To Power 9.3 lb/hp 9.2 lb/hp
Transmission 6-speed automatic 5-speed automatic
Axle/Final-Drive Ratios 3.23:1 / 2.16:1 2.65:1 / 2.20:1
Suspension, front; rear Control arms, coil springs, anti-roll bar; multilink, coil springs, self-leveling shocks,anti-roll bar Multilink, coil and air springs, adj shocks, anti-roll bar; multilink, coil and air springs, adj shocks, anti-roll bar
Steering ratio 17.2:1 14.7:1
Turns lock-to-lock 2.9 2.8
Brakes, f;r 14.0-in vented disc; 14.3-in vented disc, ABS 14.2-in vented, drilled disc; 13.0-in vented, drilled disc, ABS
Wheels, f;r 18 x 8.5-in; 19 x 9.5-in cast alum 19 x 8.5-in; 19 x 9.5-in cast alum
Tires, f;r 255/45R18 99Y; 275/40R19 101Y Pirelli Euphoria 255/35ZR19 96Y; 285/30ZR19 98Y Bridgestone Potenza REO50A
Dimensions
Wheelbase 116.4 in 112.4 in
Track, f/r 62.0 / 62.8 in 62.7 / 63.1 in
Length x Width x Height 197.6 x 72.6 x 58.2 in 193.5 x 73.7 x 54.7 in
Turning circle 39.0 ft 36.7 ft
Curb weight 4376 lb 4307 lb
Weight distribution 56 / 44 % 52 / 48 %
Seating capacity 5 4
Headroom, f/r 38.7 / 37.9 in 36.9 / 36.1 in
Legroom, f/r 42.6 / 38.3 in 42.1 / 35.0 in
Shoulder room, f/r 58.6 / 57.4 in 56.2 / 56.0 in
Cargo volume 13.8 cu ft 15.8 cu ft
Test Data
Acceleration to mph
0-30 1.9 sec 1.8 sec
0-40 2.7 2.4
0-50 3.7 3.2
0-60 4.8 4.3
0-70 6.3 5.3
0-80 8.0 6.5
0-90 9.8 8.1
0-100 11.9 9.8
Passing 45-65 mph 2.3 sec 2.0 sec
1/4 mile 13.3 sec @ 105.7 mph 12.5 sec @ 114.5 mph
Braking, 60-0 mph 114 ft 116 ft
Braking, 100-0 mph 317 ft 320 ft
Lateral acceleration 0.90 g avg 0.91 g avg
Top-gear revs @ 60 mph 1650 rpm 1800 rpm
Consumer Info
Base price $77,090 $89,075
Price as tested $77,090 $94,195
Stability/traction control Yes/yes Yes/yes
Airbags Dual front, front sides, f/r curtain Dual front, front sides, f/r curtain
Basic warranty 4 yrs / 50,000 miles 4 yrs / 50,000 miles
Powertrain warranty 4 yrs / 50,000 miles 4 yrs / 50,000 miles
Roadside assistance 4 yrs / 50,000 miles Unlimited
Fuel capacity 17.5 gal 21.1 gal
EPA city/hwy econ 14 / 20 mpg 14 / 20 mpg
MT fuel econ 17 mpg 18 mpg
Recommended fuel Unleaded premium Unleaded premium
*SAE certified