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This article was first published in 2005.
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Mercedes-AMG has released the world’s most powerful naturally aspirated production car V8, a
6.3-litre engine that harks back in capacity – if not technology – to one of the
great V8s in Mercedes history. With an output of 375kW (510hp) at 6800 rpm, the
all-aluminium engine incorporates a bunch of technological innovations including
a variable intake manifold with two integrated throttle flaps. Peak torque is
630Nm at 5200 rpm, with 500Nm available from just 2000 rpm....
The engine shares no components with any other Mercedes-Benz V8 engine and
differs from other Mercedes V8 engines in the cylinder spacing, block concept,
bore/stroke ratio and valvetrain.
Intake System
The variable intake system is die-cast from magnesium. It uses a streamlined
internal design and a vertical arrangement of intake and exhaust ports. The two
internal electronically-operated throttle flaps can be fully opened in 0.1
seconds, giving better response. The air intake is a dual-flow design with two
hotwire airflow meters.
Valvetrain
The 32 valves are operated by bucket tappets. The intake valves are 40mm in
diameter and the exhaust valves 34mm. Valve clearances are adjusted
hydraulically. All four camshafts are continuously variable over a range of 42
degrees with the camshaft timing variation controlled
electro-hydraulically.
Block
The block uses a closed-deck design with a main bearing bedplate. Cast into
the alloy are steel components that improve strength and "ensure a reliable oil
supply". The engine block and cylinder heads are of cast aluminium-silicon
alloys (AlSi7 and AlSi17) with the cylinder walls coated with a twin wire arc
spraying (TWAS) process. This results in extremely low friction and wear
accompanied by outstanding long-term durability. AMG-Mercedes claim the coating
is twice as hard as conventional iron liners.
During the TWAS process, two metallic wires and an atomising gas are brought
together in a coating unit. Passing a high voltage through the tips of the wires
breaks the gas molecules down to form a plasma, and the wire tips begin to melt.
The atomising gas removes molten metal from the wire tips and sprays these
particles onto the cylinder walls to be coated, where they solidify. This is
preceded by a high-pressure water jet which roughens the cylinder walls so that
the individual sprayed particles adhere to the surface during the TWAS coating
process. The cylinder walls are then honed. During this process, the micro-pores
in the sprayed coating are partially exposed, which enables them to retain oil
when the engine is running and ensure favourable lubrication of the pistons and
piston rings.
Internals
The crank is forged 42CRMo4V steel alloy and uses five crankshaft bearings
and six counterweights. The counterweights feature heavy metal core plugs, which
mean that they can be made significantly more compact. Two lightweight
connecting rods forged by the cracking process are connected to each of the four
crank pins. The pistons are cast alloy.
Intelligent Thermostat
The temperature of the coolant is variably controlled. In the interests of
optimal in-engine friction and fuel economy, the temperature of the coolant can
for example be lowered to 80 degrees Celsius under partial load. Under full load
conditions the temperature is raised to 100 degrees "within milliseconds" to
achieve the best possible engine cooling. The thermostat controlling the coolant
temperature receives its instructions from the engine management system.
Electronic Control
All engine functions are controlled and executed by a Bosch ME 9.7 control
unit. Fuel injection, ignition, the variable intake manifold, camshaft
adjustment and variable cooling are all controlled. The microprocessor has
10,000 different characteristic maps and functions in its memory, and is able to
carry out up to 70 million individual operations per second.
Emissions
The new AMG 6.3-litre eight-cylinder engine meets all current exhaust
emission standards. Exhaust treatment begins in the air-gap-insulated manifolds,
which have a wall thickness of only 1 millimetre. All four ceramic
catalytic converters feature thin-wall substrates. A secondary air injection
system leads to higher exhaust gas temperatures and supports the heating-up
process. It appears that the management system uses the input of the oxygen
sensors to form a feedback loop at all engine loads.
Testing
Trials of the new AMG 6.3-litre eight-cylinder engine were conducted in two
stages. The development work started with analyses of basic mechanical
functions, the oil circuit, power characteristics with various intake duct and
camshaft configurations, plus the definition of fuel injection quantities, fuel
consumption and exhaust emission values – all these were studied on the dynamic
simulation test benches at Mercedes-AMG. Engines with outputs exceeding 735
kW/1000 hp can be dynamically tested in this facility.
After completion of the basic work in Affalterbach, the first test vehicles
equipped with the new AMG eight-cylinder engine were sent onto public roads and
test tracks in all the climatic regions of the earth. These tests included:
High-altitude trials in Denver, Colorado (USA), Lesotho (South Africa) and
Granada (Spain)
Heat trials in Death Valley, California (USA), Upington (South Africa),
Idiada test track (Spain) and Phoenix, Arizona (USA)
Road trials in Los Angeles, California (USA)
Cold trials in Arctic Falls (Sweden)
Various test runs on the high-speed circuits in Nardo (Italy) and Papenburg
(Germany)
Tests in the DaimlerChrysler wind tunnel
In addition, various endurance trials were carried out with the aim of
simulating the engine’s entire operating life under the most extreme
conditions:
Nürburgring north loop: The engine was tested under predominantly full load
conditions on the world’s most demanding racetrack.
Mixed road endurance trials: Testing under everyday conditions. The vehicles
were loaded to their gross vehicle weight and subjected to a defined test
program on country roads, motorways and in city traffic.
Stress endurance trials at the DaimlerChrysler test site in Papenburg:
Extreme acceleration and deceleration cycles under predominantly full load
conditions, with high stresses on the oil circuit, cooling system and fuel
supply.
Endurance trials in the hills of the Swabian Alb region: The vehicles were
loaded to their gross vehicle weight and towed a two-tonne trailer. The route
covered country roads with numerous uphill and downhill gradients, and subjected
the engine, transmission and cooling system to very high stresses.
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