2011 Mercedes-Benz CL63 AMG Uses New Twin Turbo Direct Injection 536hp V8
By OR Staff, Photography courtesy of Mercedes-Benz
AMG has been the high-performance division of Mercedes-Benz since 1999 and has been churning out high-powered luxury Vipers for years. Despite being saddled with motors, cushions, insulation, and more electronics than a Best Buy, Mercedes-Benz AMG models are capable of some serious straight-line speed.
For 2011, AMG is debuting a new 5.5-liter twin-turbo V8 in the CL63 AMG that makes 536hp @ 5,500 rpm and 590 lb/ft of torque @ 2,000-4,500 rpm, 125 lb/ft more torque than the outgoing naturally aspirated 6.3-liter V8 engine. The claimed acceleration is 0-60mph in 4.4-seconds and a top speed of 155mph. This bodes well for American movie and sports stars since the US accounts for more than 50% of all AMG sales.
Each hand-built by a single technician, the AMG engine uses direct injection (fuel injection straight into the cylinder versus the intake manifold – for a finer atomization and cooling of the cylinder), twin exhaust manifold-integrated turbochargers, a healthy 14.7-psi of boost pressure, 10:1 compression ratio, and a new cooling system that routes coolant through the cylinder head for greater heat capacity.
All together, the new engine produces more power and gets better fuel economy than the old engine. For street cars, we’ve always been fans of forced induction.
We’ve experienced various incarnations over the years and each one has been gifted with mountains of torque and incredible acceleration capability – Autobahn qualities. They don’t handle quite like a Lotus Exige but, then again, your driver won’t mind.
From Mercedes-Benz:
Twin Turbos and Direct Injection
The new engine features twin turbochargers – one for each bank of cylinders. Welded directly to the exhaust manifold, the exhaust-driven turbochargers force intake air into the engine at a pressure of up to 1.0 bar, or about 14 pounds per square inch above normal atmospheric pressure. The engine’s compact layout includes an air-water intercooler nestled in the “V” of the engine – where the intake manifold is located on a conventional V8 engine.
Like its predecessor, the new engine features aluminum cylinder heads, pistons and cylinder block with cast-in Silitec cylinders, as well as a crankshaft, connecting roads and valves made of special forged steel. The AMG V8 has a 10.0-to-1 compression ratio – relatively high for a turbocharged engine. However, pistons crowns are four millimeters thicker to handle the higher combustion pressures, while shorter connecting rods allow existing block dimensions to be retained.
Among the many special AMG touches on the new engine are “pulsation holes” drilled through the internal webs of the cylinder block. While up-and-down movement of the pistons usually pushes air around inside the crankcase and robs power, the pulsation holes allow this internal air pressure to be better equalized between cavities, actually increasing power as a result.
The Third Generation of Mercedes-Benz Direct Injection Systems
The fuel system in the new bi-turbo V8 represents the third generation of modern Mercedes-Benz gasoline direct injection systems, and the first to be offered in the U.S. market. System pressure of the electronic direct injection system is similar to less precise mechanical injection systems – up to 200 bar or 2,840 psi.
The new V8 makes use of industry-leading electronics technology first used on Mercedes-Benz diesels – piezo-electric fuel injectors that spray gasoline directly into the combustion chambers. In the past, nearly all gasoline engines have used indirect port fuel injection.
Crystals are the Heart of the New System
Instead of conventional mechanical injector valves, piezo injectors feature a piezo-ceramic crystalline element that, in microseconds, simply changes shape when electrical current is applied. The blazingly fast piezo injectors make it possible to design very sensitive and precise injection systems, including the ability to program several small injections with each piston stroke. This is especially impressive, considering that engines idle at about 20 strokes per second and 200 strokes every second at high speeds.
The first injection is sprayed into the combustion chamber as the piston is descending on the intake stroke. Depending on speed, load and temperature conditions, another injection or two takes place during the compression up-stroke before ignition, forming a stratified mixture. A fourth injection can stabilize combustion if it’s needed. Among other things, this advanced spray-guided combustion process demonstrates the potential of the internal combustion engine for continued development and refinement.
More Efficient Cam Chain Drive
Mounted on the ends of the intake and exhaust camshafts, the hydraulic camshaft adjusters that vary valve timing are now 35 percent faster, and with a wider range of 40 crankshaft degrees, yet are more than a half inch smaller in height and width.
These smaller valve timing adjusters are made possible by a new cam chain drive system, in which the crankshaft drives an intermediate shaft above the crank. In turn, the intermediate shaft drives two short chains – one for each cylinder bank – that loop around the intake and exhaust camshaft drive sprockets. The new chain drive results in less tension and lower chain dynamics, for even lower friction and less noise.
A fourth chain drives a new variable vane-type oil pump in the bottom of the engine. At low engine speed and load, the oil pump only generates about 28 psi (or two bar) of oil pressure, and nozzles that spray cooling oil on the pistons are off. As engine speed and load increases, oil pressure goes up, and the oil spray nozzles are turned on. In this way, less energy is used when less cooling and lubrication is needed.
Three-Phase Low-Load Cooling System
Even the cooling system is significantly refined in the new engine, beginning with a two-stage flow circuit through the cylinder head. This improved coolant flow results in better heat dissipation, despite lower coolant circuit pressure, so that the water pump uses less engine power.
Start-Stop System with Direct-Start
Whenever the engine is automatically turned off to save fuel, the engine computer decides which piston is in the best position for first ignition. The direct fuel injection and multi-spark systems work with a starter motor to re-start the engine almost instantly. In the future, this new technology may actually be used to start engines without using a conventional starter motor.
