Much of the material in Sections 813, 814, 815 and 816 has been extracted from materials provided by Rotating and Reciprocating Specialists.
The purpose of this analysis is to:
• Optimize fuel consumption, and
• Detect mechanical problems before they become serious enough to cause significant damage to the machine.
Typical combustion patterns are depicted on Figure 800-5 and may be defined as follows:
1. Normal Combustion—Ignition timed correctly, proper air/fuel mixture, no malfunctions.
2. No Combustion (Dead miss)—Cause: ignition or mixture, also water in cylinder.
3. Early Combustion—Cause: ignition timing, mixture, or temperature.
4. Late Combustion—Cause: late ignition, mixture (rich or lean) or water in cylinder.
– Terminal pressure high—rich mixture
– Terminal pressure low—lean mixture
5. Detonation (too rapid combustion rate—uncontrolled)—Cause: mixture, excess load. Rich mixture tends to detonate.
6. Pre-ignition (auto-ignition)—Cause: hot spot, carbon or foreign matter in the combustion chamber, excess cylinder temperature, presence of heavy hydrocarbons.
