© Jones & Bartlett Learning, LLC. An Ascend Learning Company. NOT FOR SALE OR DISTRIBUTION chapter 6 Basic engine terminology and Operating principles
Intake and Exhaust Ports
Outer Connecting Rods
Outer Piston Slide
Inner Connecting Rods
Outer Piston (Intake)
Inner Piston (Exhaust) Left Cylinder
FIGURE 6-39
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Outer Piston (Exhaust)
Inner Piston (Intake) Crankshaft
Right Cylinder
The EcoMotors engine uses opposed pistons and a two-stroke operating cycle.
Engine Brake Systems
Lubrication Systems
Because diesel engines have less natural retarding force to slow a vehicle than a throttled SI engine, diesels often have an enginebased braking system to supplement service brake operation. Compression release brakes slow the vehicle by releasing compressed air from the cylinder near TDC. Exhaust brakes use exhaust backpressure to slow the vehicle by increasing resistance to engine rotation. When the flow of the exhaust gas through the exhaust system is restricted, the cylinders must work harder to force gases out the exhaust pipe.
The primary purpose of lubrication systems is to lubricate moving engine parts to reduce friction. Lubrication systems also: ■ clean and carry away soot and contamination from cylinder walls and internal engine parts ■ cool engine parts such as pistons ■ enhance the gas-tight sealing of piston rings to cylinder walls ■ reduce engine noise from metal engine part contact
Fuel Systems Diesel engines use high- and low-pressure fuel systems. Low-pressure fuel systems transfer fuel to high-pressure injection systems after cleaning and conditioning the fuel. High-pressure systems essentially meter and pressurize the amount of fuel required for injection. Pressurized fuel is sprayed into the cylinders where it is atomized at the correct time to achieve optimal combustion.
Air Induction and Exhaust Systems Gas or air flow through an engine is another major engine subsystem. The air induction system is responsible for providing fresh, clean, cool, dry, filtered air to the engine. The exhaust system removes the excess heat and combustion gases from the engine’s cylinders.
FOR SAMPLE PURPOSES ONLY. NOT ALL CONTENT IS FINAL 9781449624118_CH06_Pass02.indd 191
06/10/15 3:29 PM