Car Tuning Fuel and Ignition Management 3

Question 1

What is 'MBT' timing in engine tuning?

Accepted Answer

Minimum advance for Best Torque — the timing that produces maximum torque without knock

Answer

MBT is the optimal ignition advance point that produces the highest torque output; any additional advance risks detonation without further torque gain.

Question 2

A fuel injector is rated at 440 cc/min at 43.5 psi. If rail pressure is raised to 58 psi, how does flow change?

Accepted Answer

Flow increases proportionally to the square root of the pressure ratio

Answer

Injector flow scales with the square root of the pressure differential, so a moderate pressure increase yields a modest flow increase, not a linear one.

Question 3

What is the stoichiometric air-fuel ratio for E85 ethanol fuel?

Accepted Answer

Approximately 9.8:1

Answer

E85 has a stoichiometric AFR of roughly 9.8:1, requiring significantly more fuel than gasoline's 14.7:1 to achieve complete combustion.

Question 4

What does 'VE table' stand for in standalone ECU tuning?

Accepted Answer

Volumetric Efficiency table — a map defining how much air the engine actually ingests vs. theoretical maximum

Answer

The VE table is the primary fueling map in speed-density systems, representing engine breathing efficiency across the RPM and load axes.

Question 5

Why do high-performance engines often use individual throttle bodies (ITBs) instead of a single throttle body?

Accepted Answer

Each cylinder gets its own unrestricted airflow path, improving throttle response and high-RPM VE

Answer

ITBs remove the shared plenum restriction, giving each cylinder a direct air column that improves high-RPM breathing and sharpens throttle response.

Car Tuning Practice Test

Car Tuning Practice Test

Car Tuning Fuel and Ignition Management 3