Since more fuel is metered per cycle, more fuel is injected
per cycle, and more torque is produced.
Theory of Operation - STC
Step Timing Control, commonly referred to as STC, con-
trols the engine timing in an effort to minimize white
smoke at cold engine start-up and meet Federal emis-
sions standards.
Refer to Step Timing Control Familiarization, Bulletin No.
3387380, for additional information on STC.
STC has two stages of injection timing. The engine op-
erates in the ADVANCED mode of injection timing during
starting and light engine load conditions, and at NOR-
MAL timing during medium to high engine load conditions.
STC offers many advantages. During ADVANCED injec-
tion timing, it:
• Improves cold weather idling characteristics
• Reduces cold weather white smoke
• Improves light load fuel economy
• Reduces injector carboning
STC
Advanced Normal
Starting and Light Load
High Load
Advanced Timing
• Improves Cold-Weather Idling
Characteristics
• Reduces Cold-Weather White Smoke
• Improves Light-Load Fuel Economy
• Reduces Injector Carboning
Section 5 - Fuel System Fuel System General Information
N14 Page 5-7
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