Audi. Saturday , November 04th , 2017 - 12:51:46 PM
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.
In the induction tract, the intake valves close well before the piston reaches bottom dead center. This very short opening time keeps the fresh gas flow comparatively small. When the piston moves back up again after reaching bottom dead center, the compression phase starts later than usual. This allows a high geometric compression ratio of 10.0:1 - the combustion then takes place in a relatively small volume. In comparison to the short compression phase, the expansion phase is extended, which results in a high level of efficiency.
The chain drive uses a new concept to reduce the drive power required: the crankshaft drives the balancer shaft via gears, with the shaft lying far down in the V of the cylinder banks. From here chains run to the four camshaft sprockets. These are trioval in shape, i.e. they have a slightly triangular shape, in order to compensate for peak forces. The balancer shaft rotates on roller bearings with particularly low levels of friction.
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