Audi. Saturday , November 04th , 2017 - 12:40:09 PM
The 2.9 TFSI was derived from the 3.0 TFSI used in the Audi S5. Because of the greater forces inside the engine, the valve lift has been shortened by 3 millimeters (0.1 in) to 86 millimeters (3.4 in). With its unchanged bore of 84 millimeters (3.3 in), the displacement is 2,894 cm3. The crankcase integrates thin-walled cylinder liners made of gray cast iron and the crankshaft main bearing has a 2-millimeter (0.08 in) larger diameter compared with the 3.0 TFSI.
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.
Each of the two turbochargers on the 2.9 TFSI is assigned to a single cylinder bank and can build up a maximum of 0.95 bar charge pressure. Like with all new V6 and V8 engines from Audi, the turbochargers are installed within the 90-degree angle of the cylinder banks, and thus the exhaust side of the cylinder heads is on the inside, while the intake side is on the outside of the engine. This layout enables compact construction and short gas flow paths with minimal flow losses - the 2.9 TFSI responds extremely spontaneously to movement of the accelerator pedal.
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