Engine Performance & Tuning Flashcards

On a VW TSI engine, what does the term 'stratified charge combustion' refer to?

Answer: Injecting fuel directly into the cylinder in a layered pattern near the spark plug for lean-burn operation

Stratified charge combustion injects a rich fuel cloud directly near the spark plug while the rest of the cylinder contains a lean air mixture, enabling ultra-lean part-load operation.

A VW 2.0T EA888 Gen 3 engine uses an integrated exhaust manifold in the cylinder head. What is the primary performance benefit?

Answer: Improved cold-start emissions by reducing catalytic converter light-off time

The integrated exhaust manifold reduces thermal mass in the exhaust path, allowing the catalytic converter to reach operating temperature faster during cold starts, improving emissions compliance.

When diagnosing a VW TDI with reduced power and black smoke under load, which component should be inspected first?

Answer: Turbocharger variable vane mechanism stuck or seized

A seized or stuck variable vane (VNT) turbocharger cannot build adequate boost pressure, resulting in rich combustion, black smoke, and significant power loss under load.

On VW engines equipped with Cylinder Deactivation (ACT), which cylinders are typically deactivated on a 4-cylinder engine?

Answer: Cylinders 2 and 3

VW's ACT system deactivates the inner cylinders 2 and 3 on 4-cylinder engines, which minimizes engine vibration by maintaining balance across the remaining active cylinders.

A VW technician measures compression on a 2.0 TSI and finds cylinder 3 reads 145 psi while others read 190 psi. A wet compression test brings cylinder 3 to 185 psi. What is the most likely diagnosis?

Answer: Worn piston rings on cylinder 3

A significant rise in compression during a wet test (oil added to cylinder) indicates worn piston rings, as the oil temporarily seals the ring-to-cylinder wall clearance.

What does TFSI stand for in VW/Audi engine designations, and what technology does it specifically indicate?

Answer: Turbocharged Fuel Stratified Injection — indicating both turbocharging and direct fuel injection

TFSI stands for Turbocharged Fuel Stratified Injection, combining a turbocharger with FSI direct injection technology for improved power density and efficiency.

On a VW EA211 engine with active engine mounts, what triggers the control module to stiffen the mounts during cylinder deactivation?

Answer: Changed vibration frequency from 4-cylinder to 2-cylinder firing pattern requiring different damping

When cylinders 2 and 3 deactivate, the engine's firing frequency changes, requiring the active mounts to adapt their stiffness to suppress the different vibration characteristics of 2-cylinder operation.