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Mercedes-Benz AMG 6.3-Liter V8

Ride the Future of Mercedes-Benz Performance

By: Scott Oldham

Date Posted 07-21-2005

Mario Spitzner, the director of branding, marketing and sales at
Mercedes-AMG, raises his voice to be heard over the two AMG CLK DTM
coupes screaming past down the front straight. "What makes AMG famous,"
he yells as the cars roar by and begin another lap of the historic Paul
Ricard Formula One test track just outside Marseille, France, "is
torque."

Mario may as well have said Michael Jackson is bizzaro. AMG is the king
of torque, and everybody knows it. The supercharged 5.5-liter V8 in the
first of the two AMG CLKs to fly past makes 579 pound-feet, and the
twin-turbocharged 6.0-liter V12 in an AMG SL65 makes 738 lb-ft. A Dodge
Viper is only packing 500.

But all that torque, while good for turning tires, can eat
transmissions like the Cookie Monster let loose on a plate of
oven-fresh oatmeal raisin. And that is why the entire present range of
AMG cars equipped with the supercharged V8 or the twice-turboed V12 are
also equipped with the company's archaic five-speed automatic
transmission. The five-speed has a torque capacity of 796 lb-ft, while
Mercedes' new seven-speed can only handle 542 lb-ft.

What to do?

Well, if you're Mercedes-Benz, you instruct AMG, your in-house tuning
firm, to design a new normally aspirated engine that delivers more
horsepower, but less torque. Less than 542 lb-ft. That way, the
company's fleet of super-high-performance cars can benefit from the
added gears of the seven-speed.

The Recipe
AMG went to work and designed its first all-new production engine in 30
years. An engine with four valves per cylinder, all-aluminum
construction, a variable intake manifold made of magnesium, variable
camshafts, a lofty 11.3-to-1 compression ratio, and the world's first
use of a special low-friction cylinder wall coating called
twin-wire-arc-sprayed (TWAS), which is a complicated process borrowed
from the company's racing program.

It starts with a high-pressure water jet that roughens the cylinder
walls. Then two metallic wires and an atomized gas are brought together
and high voltage is passed through the tips of the wires, which begin
to melt. The gas then removes molten metal from the wire tips and
sprays those particles onto the cylinder walls, where they solidify.
The cylinder walls are then honed to perfect the surface.

The engine's bucket tappets that control the valves are also borrowed
from the racing program. AMG says the space-saving design allows for a
stiff valvetrain and therefore higher engine speeds with large valve
openings and ultimately more power.

The desire for higher-rpm capability also necessitated the design of a
new engine block. AMG changed everything, from the distance between
cylinders to the structure of the crankcase to the bore/stroke ratio.

Other tech highlights include conical exhaust-valve springs to dampen
vibration, and double-intake-valve springs to better control the large
intake valves. "In a normally aspirated engine," says Bernd Ramler, a
director of powertrain at AMG, "you need to close the intake valve
quickly."

He pauses as the lapping CLKs roar past. "You also need more intake
capacity because the air coming in is no longer pressurized. This
engine has two 70mm throttle bodies. The supercharged 5.5-liter has
one."

Dinner's Ready
The resulting engine is awesome. It measures 6.2 liters, revs to 7,200
rpm and delivers 503 hp at 6,800 rpm and 456 lb-ft of torque at 5,200.
It's the second most powerful normally aspirated production V8 in the
world behind the 7.0-liter V8 in the 2006 Chevrolet Corvette Z06, which
is rated at 505 hp and 470 lb-ft.

Plus, it emits less carbon monoxide and hydrocarbon than the blown
5.5-liter, and it weighs 55 pounds less, mainly due to the elimination
of the heavy supercharger. "The weight loss was one of the points of
going to normally aspirated," says Jan Stotz, who is the head of
project management at AMG. When we asked him what his title means, he
said, "This engine is my baby."

Endurance Trials
And his baby has been put through the ringer.

First, AMG says the engine was subjected to in-vehicle trials on every
continent in the world, including high-altitude trials in Denver,
Colorado; heat trials in Upinton, South Africa; road trials in Los
Angeles; cold trials in Arctic Falls, Sweden; and full-load testing on
the world's most challenging racetrack, the Nurburgring north loop in
northeast Germany.

Then the cooling and fuel systems were tested on two high-speed
European tracks and in DaimlerChrysler's wind tunnel in Auburn Hills,
Michigan. And then, just to be sure, it towed 2-ton trailers through
Germany's hilly Swabian Alb region and proved itself on AMG's new
high-tech test benches at its headquarters in Affalterbach, Germany.

One Man, One Engine
Satisfied with the V8's performance and durability, AMG ramped up
production at Affalterbach, where each unit is built by hand by one
man. The technician assembles the entire engine, from the installation
of the crankshaft right up to the addition of the engine oil. He then
checks the engine's operation on a cold-test bench and confirms his
pride in his craftsmanship by his signature on the AMG engine badge.

The AMG engine shop has three stories, 107,000 square feet of floor
space and an output of about 100 engines a day. Those engines are
tracked by a new electronic production documentation system called "AMG
Trace." It documents various process parameters such as the tightening
torques of all bolts, fluid levels and test results. AMG says the
state-of-the-art system guarantees production quality at the highest
level.

On the Track
Strapped into the bright orange CLK DTM racecar, we reach over and hit
the toggle switch marked "ASR off." That's Anti-Slip Regulation. You
know, traction control. With it off, we can properly get a feel for the
power delivery of the new V8 which powers this beast. It's teamed with
the same seven-speed automatic it will partner with in production
models.

Out on the track, we immediately notice what a good combination the
engine and transmission is, at least on a racetrack. Tight gear spacing
keeps the engine up in its powerband, and the big V8 pulls hard into
its rev limiter. The engine doesn't rev quickly like a smaller engine
might. Instead, it builds revs slowly and smoothly. And with the
traction control shut down, it has the power to spin the CLK's 20-inch
race-spec Dunlops out of the lower-speed corners. By 2,000 rpm the V8
is already making 362 lb-ft of torque, which climbs to 405 lb-ft by
3,000 rpm. It might not be as much as the supercharged 5.5-liter engine
produces, but it's plenty.

This is also one of the best-sounding V8s we've ever heard. AMG
developed a new twin-pipe exhaust system with pipe cross-sections and
silencer volumes precisely suited to the engine's displacement. At idle
it sounds like a 1960s muscle car, but its voice takes on a whole new
dimension as it travels through its rev range. Think Nextel Cup car,
but with a higher pitch and a more melodic tone, while the blown
5.5-liter in the other CLK DTM throws a deep rumble.

Buy One Soon
The drivetrain will debut in the ML63 AMG, which will be shown at the
Frankfurt Motor Show in September. After that, expect a C63, an E63, an
R63, a CLK63, an SLK63, an S63 and a CL63. We expect the A-Class will
be immune.

And just in case you're wondering why this 6.2-liter engine (it
measures 6,208cc) is being called a 6.3-liter, Mercedes says it's in
tribute to the 300 SEL 6.3, which debuted in 1968 and is the great,
great, great grandfather of today's E55. Don't let it bother you. The
5.5-liter it's replacing only measures 5,439cc.

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