Autonatomy · 07.4 Ignition, Combustion & Timing Control

Training boundary: The timing diagram, cases and values in this course are fictional teaching models. No slider value is an OEM spark specification, safe programming command or repair instruction. Ignition circuits are high-voltage hazards; actual service requires qualified supervision and current vehicle-specific procedures. This module focuses on gasoline spark ignition; diesel compression ignition operates differently.

Ignition & Combustion Explorer

Explore eight inputs, circuits and physical events that connect a controller request to actual cylinder contribution.

Four Ignition Journeys

Trace timing, spark delivery, misfire diagnosis and abnormal-combustion reasoning using fictional examples.

Ignition Timing Lab · Degrees Versus Time

Explore an idealized gasoline four-stroke cycle with a single cylinder, compression TDC at 360° in a 720° cycle, and one fictional spark near the end of compression. Actual valve events, ignition strategy, flame development and pressure peak vary by engine. No value below is a specification, tuning recommendation or real test command.

Illustrative crank angle: 340°Fictional spark advance: 20° BTDCIllustrative engine speed: 1800 RPM

Solid line: selected crank angle. Dashed line: illustrative scheduled spark. Diagram is intentionally not a real ignition waveform or combustion-pressure trace.

Selected strokeCompression

Fictional spark event340° crank angle

Time from spark to compression TDC1.85 ms

Event location at selected angleSpark event

The Challenger asks · Same angle, different time

A fictional spark is requested 20 crank degrees before compression TDC. Engine speed rises from 1,000 RPM to 2,000 RPM while the 20° advance stays the same. What changes?

Classroom relationship: degrees/second = RPM × 6, so milliseconds between spark and TDC = (advance ÷ (RPM × 6)) × 1,000. The actual combustion start, flame speed, pressure peak and optimal timing are not calculated here.

Continue with the existing Autonatomy ignition resource

Ignition Timing Lab remains available separately, along with the mapped Ignition Timing & Spark Advance lesson in the Course Player.

Ignition Diagnostic Decisions

Six fictional shop scenarios. Distinguish the controller’s request from spark delivery and physical cylinder response, and stop unsafe high-voltage testing.

07.4 · Knowledge Check

Answer all ten questions to record a browser-local knowledge score. This is not a vehicle test result, shop authorization, or observed hands-on competence.

Keep learning

Return to Course Player · Review: Engine Management 07.1 · Review: Fuel Delivery 07.3 · Earlier Ignition Timing Lab

Both previously mapped 07.4 ignition resources remain available alongside this original module.