ABA Engine Performance & Tuning 2

Question 1

What is the stoichiometric air-fuel ratio for gasoline engines?

Accepted Answer

14.7:1

Answer

The stoichiometric air-fuel ratio for gasoline is 14.7:1, meaning 14.7 parts air to 1 part fuel for complete combustion.

Question 2

Which sensor directly measures the mass of air entering the engine?

Accepted Answer

MAF sensor

Answer

The Mass Air Flow (MAF) sensor directly measures the mass of air entering the intake, allowing the ECU to calculate fuel delivery.

Question 3

What does advancing ignition timing beyond the optimal point typically cause?

Accepted Answer

Engine knock/detonation

Answer

Over-advancing ignition timing causes the fuel-air mixture to ignite too early, resulting in knock or detonation that can damage pistons and bearings.

Question 4

A lambda value of 0.85 indicates the engine is running:

Accepted Answer

Rich of stoichiometric

Answer

Lambda below 1.0 indicates a rich mixture (excess fuel), while above 1.0 indicates a lean mixture; 0.85 means 15% more fuel than stoichiometric.

Question 5

What is the primary purpose of a blow-off valve (BOV) in a turbocharged engine?

Accepted Answer

Release excess boost when throttle closes

Answer

A blow-off valve vents pressurized air from the intake tract when the throttle closes, preventing compressor surge and protecting the turbocharger.

(ABA) American Board of Audiology Practice Test

(ABA) American Board of Audiology Practice Test

ABA Engine Performance & Tuning 2