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..