Niamh Hart. Audi. October 13th , 2017.
In the classic Miller cycle, the reduced cylinder charge is detrimental to torque and power output. These aspects have been neutralized by Audi thanks to the implementation of turbocharging and the two-stage Audi valvelift system (AVS). The four camshafts of the 2.9 TFSI can each be adjusted by 50 degrees crank angle. At higher load and engine speed ranges, AVS closes the inlet valve later. The opening time increases from 130 to 200 degrees crankshaft angle, while at the same time the valve lift increases from 6.0 to 10.0 millimeters (0.2 to 0.4 in). Cylinder charging also increases considerably - the 2.9 TFSI revs up powerfully and delivers an impressive output.
An important component of the B-cycle combustion process is the central position of the injectors in the combustion chamber. In the area around the inlet valve, this makes possible a geometry which, in interaction with the inlet ports, allows for targeted mixing up of the gas charge. The common-rail system injects the fuel into the combustion chamber with 250 bar of pressure - the high injection pressure ensures a homogeneous spray pattern and consequently a uniform propagation of the flame front.
The front strut domes are made of highly integrated cast aluminum parts. Compared to sheet steel components made of many individual parts that are welded together, they are eight kilograms (17.6 lb) lighter. This construction allows a very stiff connection between the upper links and the body for the best-possible steering response - optimal conditions for dynamic handling.
A further efficiency component of the 2.9 TFSI is the thermal management system. The crankcase and the cylinder head have separate coolant circuits. After a cold start, the switchable water pump controls the flow of coolant through the engine so that the oil is warmed up as quickly as possible. The exhaust manifolds are integrated in the cylinder head, and coolant circulates around them which helps ensure rapid warming up. When the engine is warm, this technology lowers the exhaust temperatures - consumption drops drastically, especially when driving in a sporty way. The great efficiency of the V6 bi-turbo is also partly to do with low friction. For example, the fully adjustable oil pump only builds up as much pressure as necessary.
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