Car Tuning Fuel and Ignition Management 5

Question 1

What is the purpose of an aftermarket piggyback ECU like a Hondata or EcuTek tune versus a full standalone ECU?

Accepted Answer

A piggyback or reflash modifies or intercepts stock ECU signals while retaining OEM hardware and integration

Answer

Piggyback and reflash solutions work with the factory ECU to alter maps and signals, preserving OEM features like traction control and diagnostics that a standalone might lose.

Question 2

What does 'injector dead time' (also called offset or latency) account for in ECU calibration?

Accepted Answer

The delay between the ECU command and when the injector actually begins to flow fuel

Answer

Injector dead time is the electrical and mechanical delay before fuel flows; the ECU adds this value to the calculated pulse width so actual fuel delivery matches the target.

Question 3

How does adding a larger-displacement fuel injector affect idle quality if the ECU calibration is not updated?

Accepted Answer

Idle becomes rough and rich because the ECU commands the same pulse widths that now deliver too much fuel

Answer

Larger injectors flow more fuel per millisecond, so uncorrected OEM pulse widths over-fuel the engine, causing a rich, lumpy idle until injector scaling is updated in the calibration.

Question 4

What is 'ignition phasing' or 'spark scatter' and why is it harmful?

Accepted Answer

Inconsistent spark timing from cycle to cycle that causes combustion variation, power loss, and potential engine damage

Answer

Spark scatter from failing sensors, trigger wheel issues, or coil problems causes each cylinder to fire at slightly different crank angles, producing rough running and potentially destructive pressure spikes.

Question 5

Why do high-compression naturally aspirated engines often require premium fuel even without forced induction?

Accepted Answer

Higher compression raises end-gas temperature and pressure, increasing the risk of auto-ignition before the spark fires

Answer

Compression alone significantly increases in-cylinder temperatures and pressures at TDC, making the charge susceptible to detonation unless a higher-octane fuel resists premature auto-ignition.

Car Tuning Practice Test

Car Tuning Practice Test

Car Tuning Fuel and Ignition Management 5