Chapter 1 Engine Operation Objectives Explain principals of
Chapter 1 Engine Operation
Objectives • Explain principals of internal combustion engine operation • Identify internal combustion engine parts by name • Explain various engine classification 2
Simple Reciprocating Engine • • Cylinder Piston Connecting rod Crankshaft 3
Simple Reciprocating Engine 4
Four Stroke Engine Operation • • Intake stroke Compression stroke Power stroke Exhaust stroke 5
Four Stroke Engine Operation 6
Compression Ratio • Comparison of volume at BDC and at TDC • If compression ratio is 8: 1 – Mixture is compressed to one-eighth its original volume • If compression ratio is 12: 1 – Mixture is compressed to one-twelfth its original volume 7
Compression Ratio 8
Cylinder Arrangement • Up to eight or more cylinders (3, 4, 5, 6, 8) • Arranged inline – V style or opposed 9
Cylinder Arrangement 10
Camshafts • Control the rate at which engine breathes • Located in either block or cylinder head • Driven by crankshaft using gears, chain, or belt • Turn one-half speed of crankshaft 11
Camshafts 12
Cylinder Block • • Includes oil galleries and water jackets Can be constructed from cast iron or aluminum Cast around a sand or foam mold called a core In lost foam casting (LFC) the form is “lost” or burned during the pour – Made of expendable polystyrene beads (styrofoam) • V type blocks are cast in two rows – Called banks 13
Short and Long Block • Short blocks – Crankshaft, pistons, rods, camshaft, and cam drive components • Long block – Short block plus cylinder heads 14
Short and Long Block • Oil pan, flywheel, harmonic balancer and timing chain cover may be mounted on both the short and long block 15
Engine Displacement • Engines classified by their displacement • Displacement is total volume pistons displace in cylinders • Formula to determine displacement – Bore² × Stroke ×. 7854 × Number of cylinders 16
Engine Displacement 17
Valve Arrangement • Modern engines use and overhead valve (OHV) arrangement known as I-head or valve-in-head 18
Combustion Chamber Designs • Primary designs – Hemi, wedge, pent-roof, stratified charge • Combustion chamber – Area in cylinder head into which air-fuel mixture is compressed 19
Combustion Chamber Designs • Turbulent and nonturbulent designs – Turbulent • Wedge – Nonturbulent • Hemi 20
Combustion Chamber Designs 21
Direction of Crankshaft Rotation • Front of engine is side opposite the transmission • Longitudinally mounted engines turn clockwise when viewed from the front • Transverse mounted engines also follow this standard – Although a few engines (ie Honda) rotate in the opposite direction 22
Firing Order • Sequence in which cylinders fire • Firing order typically does not follow cylinder numbering • An example of a v 8 firing order – 18436572 23
Firing Order 24
Companion Cylinders • Engine with even number of cylinders will have companion cylinders • Pair of pistons go up and down together • One cylinder on compression stroke while other is on exhaust stroke 25
Engine Cooling • Use both air cooling and liquid cooling • As engine temperature rises – Amount of NOx (oxides of nitrogen) rises • Liquid cooled engines have water jackets to cool areas around cylinders • Coolant is moved through system by water pump 26
Engine Cooling 27
Engine Cooling • Coolant mixture – 50% coolant and 50% water • Dissimilar metals found in engine can cause electrolysis in coolant – Causes corrosion and deterioration of metals 28
Spark and Compression Ignition • Conventional spark ignition systems – Spark plug to ignite air-fuel mixture • Diesel engines – Compression of engine to ignite air-fuel mixture 29
Spark and Compression Ignition 30
Two Stroke Cycle • Outboards, chainsaws, motorcycles • Power stroke every revolution in crankshaft • Oil must be mixed with gasoline – Lubricates lower engine bearings 31
Two Stroke Cycle 32
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