1. Fuel System Principles
St. Cloud Technology Education
Course: General Automotive Service

2. Common Themes Convert Chemical Energy to Kinetic Energy Increase Power
Increase Efficiency
Operate Cleanly

3. Internal Combustion Engines
It’s all in the:
Fuel
Compression
Air/Fuel Mixture
Crankshaft Timing
Keep it clean (air & fuel)
Sensors

5. Fuel Hydrocarbons! Built from combinations of Hydrogen and Carbon
Energy produced from combustion - the breaking of the bonds between Hydrogen and Carbon atoms.
Organic - Extracted or mined
Engineered to specifications – Chemical Engineering
“A Lot of Bang for Your Buck”

6. Compression More compression = higher efficiency and more power
Compression Ratio: largest volume of the combustion chamber divided by the minimum volume of the combustion chamber.
Gasoline Engines: 10:1
Increases temperature
Ignites with spark
Diesel Engines:
higher ratios
much higher compression
Auto-Ignites without spark

7. Stoichiometric Air-Fuel Ratio
Stoichiometric Air-Fuel Ratio: the ratio of air to fuel at which exactly all the available oxygen and fuel is used completely.
Gasoline: 14.7/1
All fuels have a target Stoichiometric ratio
Lean Mixture: too much air/too little fuel, runs hot!
Rich Mixture: too much fuel/too little air, runs cold!

8. Air-Fuel Ratio Power Efficiency Emissions from Exhaust Stream
Wear & Tear

9. Air-Fuel Ratio Extreme Consequences
Too Lean. Too Rich

10. Timing Taking Advantage of the Crankshaft’s Momentum
Timing of spark can increase efficiency and power
Combustion of compressed mixture begins to expand in perfect step as the piston moves downward….

11. Timing the Spark

12. Fuel & Air Filters Dirt and Debris KEEP OUT!!!
Prevent clogging of fuel injectors
Related to air/fuel ratio.

13. Sensors EFI: Electronic Fuel Injection
Multiple sensors gather readings or inputs
Computer processes the inputs
Computer makes adjustments
amount of fuel injected
timing of when fuel is sprayed into the combustion chamber
Inputs are collected about 100 times/second

14. Part II: Components & Maintenance
In the next lesson, students will identify parts, location of parts, and review basic maintenance items.