The objective is to produce the increase in acceleration characteristic of a revolving engine, normally aspirated. The new AMG engine, instead of being diesel-type, at approximately 2,000 rpm, generates a maximum torque of 5,200 rpm and yet produces more thrust than the old between 1,000 and 2,000 rpm, with the strongest overvoltage starting at 3,000 rpm. In general, Illenberger said, “it produces a sportier delivery.
More similar to diesel are the 160 bar combustion pressures generated by the new unit, and a lighter, more robust cylinder block developed to withstand them. It is of the closed deck variety, creating a crankcase that looks more like a partially closed box than a semi-open one, with deep and reinforced skirts around the cylinders. The new alloy block is as strong as a diesel engine, Illenberger said. The 16-valve cylinder head is also new, with one of the main design challenges being the dispersion of the considerable heat generated.
Larger exhaust valves and valve seats, a redesigned water jacket, oil, water and air cooling for the turbo and separate coolant piping for the cylinder head and cylinder block allow more efficient and protective control of temperatures under the bonnet, assisted by electrically controlled water pumps. The head itself features variable inlet and outlet valve control Camtronic and dual injectors per cylinder.
A single piezoelectric injector per cylinder would be at the upper limit of its fuel volume supply, Illenberger said, so a second quartet of injectors is inside the inlet manifold sections to increase supply under strong acceleration. The Camtronic system allows two camshaft profiles to provide a combination of good fuel economy and increased throttle response.
The blades of a large turbocharger operate on low-friction roller bearings, an electric gate that minimizes pressure drop when pressure modulation is required. The turbo now lives between the engine and the front bulkhead, having rotated the cylinder head 180 degrees to fit the engine under the bottom lines of the bonnet of new models.
The new turbo location requires additional cooling, some of this thanks to the engine cover which takes the form of an air flow generated by the fan. Illenberger said electric water pumps can also run after the engine is turned off to cool the block, head and turbo. The more powerful “S” version sometimes takes advantage of the air conditioning to cool as well.
In addition to designing an entirely new engine, AMG has also developed a more rational way of manufacturing it. Each engine is still built under the “one man, one engine” approach long used by the company (there are several women who also manually assemble these engines, by the way) – the electronic recording methods of the sequence of assembly of the components and the torque applied to each of their fasteners, by each power tool. The new methods save time and improve ergonomics.