Car Tuning Fuel and Ignition Management Questions and Answers

Question 1

When tuning a turbocharged engine under high boost, what is the primary reason for targeting a richer air-fuel ratio (e.g., 11.5:1) compared to the stoichiometric ratio (14.7:1)?

Accepted Answer

To prevent detonation and cool the combustion chamber.

Answer

To maximize fuel economy.

Answer

To increase exhaust gas temperature for faster spool.

Answer

To ensure complete combustion for emissions compliance.

Question 2

A tuner is adjusting ignition timing on a naturally aspirated engine. As engine RPM increases at a constant load, how should the ignition timing generally be adjusted to maintain optimal power?

Accepted Answer

It should be advanced.

Answer

It should be significantly retarded.

Answer

It should remain constant across the RPM range.

Answer

It should be adjusted based on coolant temperature only.

Question 3

A customer's vehicle is being tuned using a speed-density system. Which of the following tables is most critical for the ECU to accurately calculate the necessary amount of fuel to inject?

Accepted Answer

Volumetric Efficiency (VE) table.

Answer

Ignition Dwell Time table.

Answer

Rev Limiter settings.

Answer

Radiator Fan Activation Temperature table.

Question 4

During a tuning session, the knock sensor detects detonation. Which of the following is the most appropriate immediate action for the Engine Control Unit (ECU) to take?

Accepted Answer

Retard ignition timing.

Answer

Increase fuel pressure.

Answer

Advance ignition timing.

Answer

Enrich the air-fuel mixture slightly.

Question 5

What is the primary function of adjusting 'Ignition Dwell Time' in an engine's tune?

Accepted Answer

To ensure the ignition coil has sufficient time to charge for a strong spark.

Answer

To control the duration of the fuel injector pulse.

Answer

To change the spark plug's heat range electronically.

Answer

To set the engine's base idle speed.

Question 6

Which of the following best describes the engine operating state known as 'Open Loop' fueling?

Accepted Answer

The ECU ignores sensor feedback and relies on pre-programmed fuel maps based on inputs like RPM, throttle position, and engine temperature.

Answer

The ECU continuously adjusts fuel trims based on wideband O2 sensor feedback to maintain a stoichiometric air-fuel ratio.

Answer

The fuel injectors are held fully open for maximum power, regardless of engine conditions.

Answer

The ignition system is disabled, and fuel is cut off, such as during deceleration.