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© 2012 Delmar, Cengage Learning© 2012 Delmar, Cengage Learning
Engine Classifications and
Advanced Transportation
Technologies
Chapter 16

Objectives
• Explain various engine classifications and
systems
• Know the various differences in cylinder heads
• Describe differences in operation between
gasoline and diesel four-stroke piston engines
• Explain the operation of two-stroke and Wankel
rotary engines

Objectives (cont’d.)
• Describe the differences between electric,
hybrid, and fuel cell electric vehicles
• Describe the types of hybrid electric vehicles
• Explain the operation of a hydrogen fuel cell

Introduction
• Technicians should:
– Understand the basic design configurations of
automobile engines
– Use service manuals intelligently
– Communicate with customers or peers
• After reading this chapter, you should be able to
look under the hood and identify the engine type

Engine Classifications
• Piston engines all have the same basic parts
– Differences in design
• Engine classifications
– Cylinder arrangement
– Cooling system
– Valve location and cam location
– Combustion
– Power type
– Ignition system
– Number of strokes per cycle

Cylinder Arrangement
• Automobile engines
– Have three or more cylinders
• Cylinders are arranged in several ways
– In-line: all cylinders arranged in one row
– “V” arrangement: cylinders are cast in two rows
(i.e., cylinder banks)
– Opposed to each other: suited for smaller
underhood areas

Firing Order
• Ignition interval
– Interval between power strokes
• Within two turns of the crankshaft, all cylinders
fire once
– Firing order: order in which the cylinders fire
• Companion cylinders
– Pairs of cylinders in engines with an even
number of cylinders

Engine Cooling
• Cooling systems
– Air cooling: air is circulated over cooling fins cast
into the outside of cylinders and cylinder heads
– Liquid cooling: has cavities in the block and head
castings called water jackets
• Water pump pumps coolant through the system
• Coolant mixture is designed to prevent rust and
electrolysis: 50% water and 50% anti-freeze

Valve Location
• Engines are classified by valve location
• Common arrangements
– L-head: common in motor vehicles during the
first half of the twentieth century
– I-head: used in today’s automobiles
• Less exhaust emissions
• Higher compression

Camshaft Location
• Cam-in-block engine: pushrod engine
– Camshaft has valve lifters that move pushrods
that operate rocker arms to open the valves
– Found most often on V-type engines
• Cam-in-head engine: overhead cam engine
– Camshaft is mounted on top of the cylinder head,
just above the valve
– Found in in-line engines

Other Cylinder Head Variations
• Crossflow head: intake and exhaust manifolds
are on opposite sides on an in-line engine
– More efficient in moving intake and exhaust
• High-performance breathing arrangements
– Designs can improve engine breathing
• High-performance late-model engines use multiple
valve heads

Combustion Chamber Designs
• Common combustion chamber designs
– Hemi (nonturbulent): efficient at high speeds
– Wedge (turbulent): common in pushrod engines
• Other chamber designs
– Pent-roof (V-shaped)
– Chambers shaped like a “D” or a heart
• Diesel engines
– No chamber in the cylinder head itself
• Honda
– Designed a stratified charge design

Spark and Compression Ignition
• Diesel-cycle and four-stroke gasoline engines
– Share the same basic principles
• Gasoline engine: spark ignition (S.I.) engine
• Diesel, compression ignition engines: do not use a
spark to ignite fuel
• Diesel engines
– Compression ratio: comparison between volume
of cylinder and combustion chamber
– Can run at very lean air-fuel mixtures at idle
– Have high particulate emissions

Alternate Engines
• Most vehicles use internal combustion four-
stroke piston engines
– Several other engine types have been developed
• Alternate engines found in today's vehicles:
– Wankel rotary (rotary engine): two rotors rotate
inside of a chamber
• Do not have pistons
– Two-stroke cycle engines: use a mixture of oil
and gasoline for lubrication of the crankshaft,
connecting rod, and piston

New Generation Vehicles
• Include:
– ULEVs: ultra-low emission vehicles
– ZEVs: zero emission vehicles
– EVs: electric vehicles
– PEVs: plug-in electric vehicles
• Battery EVs and hybrid EVs: several concerns
– Must carry many nickel metal hydride or lithium-
ion batteries (LIBs), which are heavy
– Specialized hazard and safety training for
emergency service personnel is needed

Regenerative Braking
• During deceleration
– Motor is used as a generator, producing
electricity to recharge batteries as it slows the
vehicle down

Hybrid Vehicles
• Advantages
– Improved fuel economy
– Increased performance
– Reduction in exhaust pollutants
• Most are powered with an internal combustion
engine or a battery-powered electric motor
• Hybrid combinations
– Series hybrid
– Parallel hybrid
– Series/parallel hybrid

Hybrid Vehicles (cont’d.)
• Major operating difference between hybrid and
conventional vehicles powered only by an
engine
– Engine in a hybrid vehicle stops running at idle
as long as certain operating conditions are met
• Improves fuel economy
• Hybrid disadvantages
– High initial costs
– Technician safety concern

Types of Hybrids
• Mild hybrid
– Vehicle moves with power supplied only by ICE
• Medium hybrid
– Added function of electric motor assist
• Full hybrids
– Do everything that medium hybrids do,
– Can also power vehicle using only the electric
motor
– Includes two-mode hybrids

Types of Hybrids (cont’d.)
• Power hybrid/muscle hybrid
– As motor speeds up but its torque remains the
same, the engine provides supplementation
• Plug-in hybrid
– Power socket allows larger batteries to be
recharged by an external source of electricity
• Plug-in recharging
– Electrical grid: interconnected network
• Moves electricity from generating stations to
customers

Hybrid Vehicle Service and
Safety
• Considerations
– Electrical shock hazard
• Conduit color designations
• Other hybrid vehicle operation, safety, and
service
– More information can be found in other chapters

Hydraulic Hybrid Vehicles
• Work in the same manner as HEVs
– Increase overall efficiency
• Run engine at its most efficient rpm
• Capture energy during braking
• Shut engine off whenever possible
– Use reservoirs, accumulators, and pumps
• Instead of batteries
• Hydraulic hybrid system operation
– High-pressure fluid is stored in accumulators at
pressures above 3,000 psi

Fuel Cell Electric Vehicles
(FCEVs)
• Generate electricity when needed
– Only exhaust by-products are water and heat
• PEM: proton exchange membrane fuel cell
– Possible internal combustion engine replacement
• Technically hybrid vehicles
– Use an electricity-generating fuel cell engine
rather than an ICE
– Has a backup battery module
– Use an electrochemical reaction to produce
electricity

Fuel Cell Electric Vehicles
(FCEVs) (cont'd.)
• Fuel cell operation
– Use hydrogen for fuel and oxygen from the air as
an oxidant
• Combining hydrogen and oxygen produces
electricity
• Fuel cell characteristics
– Never run dead
– Stacked and connected in series
– Some use an ultracapacitor
– Expensive to replace

Summary
• Piston engines share common parts but there
are many different design variations
• Cylinders are arranged in-line, in a V, or
opposed to each other
• Cylinder rows, called banks, are determined
from the flywheel end of the engine
• Crankshaft turns two revolutions to complete
one four-stroke cycle

Summary (cont'd.)
• Engines use either liquid or air cooling
• Camshaft designs: pushrod and overhead
• Each valve opens and closes 25 times per
second in an engine operating at 3,000 rpm
• Alternatives to the four-stroke piston engine are
not yet viable

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