Assignment For April 27

Read Chapter 40 fuel systems and answer the ASE questions at the end. On the graphics on page 697 shows the evolution of fuel delivery starting from the bottom diagram up. Carburetor systems were low pressure, around 3 PSI (Pounds per Square Inch) and typically had a mechanical pump attached to the engine. Because of low pressures drawn on the fuel lines from the tanks, the fuel could boil and suffer vapor lock in the lines. Fuel Injection arrived to atomize fuel delivery with a fine spray. It needed higher fuel pressures, 35-45 PSI, so the fuel pump was relocated back to the fuel tank to avoid low pressure vapor lock. Single Point Injection used one or two large fuel injectors that were common to all cylinders at the throttle body (cheap and not very effective), and Multi-Point Port Injection (superior), using several injectors, one at each cylinder, spraying right before the intake stroke. Direct Injection is the latest and greatest fuel system for gasoline engines. These use an in-tank pump to deliver fuel (~50 PSI) to an engine mechanically driven high pressure pump. The Super-fast injectors and dangerously high pressures, 750 to 3,000 PSI, can inject fuel directly into the cylinder during compression and power stroke for a more versatile, controlled, and efficient fuel burn. FYI, Diesel engines, by nature, have always used direct injection since the beginning of time.

Read Chapter 45, Exhaust systems and answer the ASE questions at the end.

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