Car Tuning Engine Performance Principles 4

Question 1

What is 'lambda' (λ) in engine tuning, and what does λ=1.0 represent?

Accepted Answer

The ratio of actual air-fuel mixture to stoichiometric; λ=1.0 means a perfect stoichiometric mixture

Answer

Lambda is the normalized air-fuel ratio where 1.0 represents exactly stoichiometric combustion (14.7:1 for gasoline), lean is above 1.0, and rich is below 1.0.

Question 2

What is the purpose of 'lobe separation angle' (LSA) in camshaft design?

Accepted Answer

It sets the angular difference between intake and exhaust lobe centerlines, affecting idle quality and powerband width

Answer

LSA is the angle between intake and exhaust lobe centerlines; a tighter LSA increases overlap and top-end power while a wider LSA broadens the powerband and improves idle.

Question 3

In a naturally aspirated engine, what is the typical effect of adding a cold air intake (CAI)?

Accepted Answer

Modest power gains of 5-15 hp by reducing intake restriction and lowering intake air temperature

Answer

A cold air intake typically yields 5-15 hp by reducing intake restriction and drawing cooler, denser air from outside the hot engine bay.

Question 4

What does 'MBT timing' stand for and why is it significant?

Accepted Answer

Minimum advance for Best Torque — the spark timing that produces peak torque without causing knock

Answer

MBT timing is the minimum ignition advance angle that produces maximum torque; advancing beyond MBT risks detonation without additional power gain.

Question 5

What is the effect of using a larger throttle body on a naturally aspirated engine?

Accepted Answer

Can improve high-RPM airflow but may hurt throttle response if oversized for the engine

Answer

A larger throttle body helps high-RPM airflow but an oversized unit makes precise throttle control difficult at low speeds and doesn't guarantee big power gains.

Car Tuning Practice Test

Car Tuning Practice Test

Car Tuning Engine Performance Principles 4