CTE Engine Performance & Tuning 3

Question 1

What is the stoichiometric air-fuel ratio (AFR) for gasoline combustion?

Accepted Answer

14.7:1

Answer

14.7:1 is the stoichiometric ratio where all fuel and air are theoretically consumed, yielding the best catalyst efficiency.

Question 2

Which ignition system component stores and releases the high-voltage energy needed to fire a spark plug?

Accepted Answer

Ignition coil

Answer

The ignition coil transforms battery voltage into the high voltage (20,000–40,000+ V) required to jump the spark plug gap.

Question 3

A student notices that spark plug electrodes are coated with black, sooty carbon deposits. This condition indicates:

Accepted Answer

Rich combustion or excessive oil burning

Answer

Black carbon fouling results from an overly rich mixture or oil entering the combustion chamber being incompletely burned.

Question 4

What does base ignition timing refer to in engine tuning?

Accepted Answer

The fixed timing set when the ECU advance is disabled or disconnected

Answer

Base timing is the initial timing reference set mechanically or by the ECU base map before dynamic advance is applied.

Question 5

Variable valve timing (VVT) systems improve engine performance primarily by:

Accepted Answer

Optimizing valve opening and closing events across the RPM range

Answer

VVT adjusts camshaft phasing to optimize power and efficiency at both low and high RPM operating conditions.

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