Volkswagen EA839 (2.9/3.0 V6 TFSI)

The Volkswagen Group's modern turbocharged V6 petrol, and the engine that replaced two quite different predecessors at once — Audi's supercharged EA837, and in the Porsche SUVs Porsche's own twin-turbo M46.

Its defining feature is the hot vee. The turbochargers and the exhaust side sit inside the 90° angle between the banks rather than outside it, and the exhaust manifolds are cast into the cylinder heads. That shortens the exhaust path and makes the engine respond quickly, and it puts the hottest part of the engine in the least accessible place on it. Everything living between the banks — turbocharger oil and coolant lines, wiring, vacuum and crankcase plumbing — ages faster than the same part would on a conventional layout and costs far more labour to reach. Oil condition is not a service-interval question here; a turbocharger fed tired oil in that position is the failure the layout invites.

Two displacements share the name and they are not the same engine. The 3.0 TFSI runs a single twin-scroll turbocharger. The 2.9 TFSI is shorter-stroked and twin-turbocharged, and it is what the S and RS cars carry. Neither the badge nor the litre figure reliably tells you which turbocharger arrangement is in front of you, so confirm it before quoting any work on the exhaust side.

The rest is what any direct-injected petrol engine of the era brings — intake-valve carbon at mileage, high-pressure fuel-pump wear — with one addition worth knowing. Many of the Audi installations carry a 48-volt mild-hybrid system, so a starting, charging or stop-start complaint on one of those cars may belong to that subsystem rather than to the engine at all.