VW Engine Performance & Tuning 2

Question 1

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

Accepted Answer

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

Answer

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.

Question 2

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

Accepted Answer

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

Answer

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.

Question 3

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

Accepted Answer

Turbocharger variable vane mechanism stuck or seized

Answer

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.

Question 4

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

Accepted Answer

Cylinders 2 and 3

Answer

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.

Question 5

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?

Accepted Answer

Worn piston rings on cylinder 3

Answer

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.

(VW) Volkswagen Certified Technicians Practice Test

(VW) Volkswagen Certified Technicians Practice Test

VW Engine Performance & Tuning 2