Like all AMG engines, a single technician is responsible for the assembly of the SL55's newly developed supercharged V8. The 5439cc engine's Lysholm-type belt-driven supercharger delivers a maximum of 11.6 psi (0.8 bar) of boost, the charge-temperature cooled by a crossflow air-to-water intercooler. Because it's connected directly to the crankshaft via an electro-magnetic clutch and a separate poly-V-belt, the blower reacts extremely quickly to the driver's foot, delivering boost just off idle. Refinements made to the 5.5L engine for the blower application include a faster-acting electronic throttle, revised cam timing, high-rate valve springs and lightweight valves. This is in addition to the AMG tweaks performed on the base 5.0-liter Mercedes powerplant. These include special cross-bolted connections (main bearings, etc.) in the crankcase; a crankshaft adapted to the high-torque motor using modified bearings and more durable material, with a stroke of 92mm; special heat-resistant forged pistons; new oil sump and more powerful oil pump; larger intake and exhaust runners in the cylinder heads for higher airflow rates; longer valve opening duration for improved charging of the combustion chambers; double spring assemblies in the valvetrain and lightweight retainers; and a modified ECU.