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Volatility
a measure of gasoline's ability to change from a liquid to a vapour.
is affected by temperature and altitude.
the more volatile it is - the more efficient the gasoline will vaporize.
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Atomization
contributes to changing gasoline from a liquid into a combustible vapour
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Vaporization
Changing a liquid such as gasoline into a vapour (gas) by evaporation or boiling
Higher the pressure - the higher the boiling point
Lower the pressure - the lower the boiling point
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Back Pressure
is the pressure created in the exhaust system by restrictions to the flow of the exhaust gases.
The higher the back pressure is, the lower the engine's volumetric efficiency is.
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Function of the Intake Manifold ?
must provide efficient vaporization and air-fuel delivery.
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Overly "Lean" combustion produces what ?
Oxides of Nitrogen (NOx)
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Overly "Rich" combustion produces ?
Unburned Hydrocarbons (HC) and Carbon Monoxide (CO)
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Name 3 points about "Single Plane Manifolds"
uses short runners to connect all of the engine's inlet ports to a single common plenum.
permits more equal cylinder-to-cylinder mixture distribution at high rpm
can produce more horsepower at high rpm than dual plane.
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In-Line engines usually hav _________ manifolds.
Single Plane
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Name 2 points about "Dual Plane Manifolds"
has two separate plenum chambers connected to the intake ports of the engine.
mixture velocity is greater at low-to-intermediate rpm than w/ the single plane manifold at high rpm.
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Where are dual plane manifolds commonly found ?
V-Engine configuration
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Throttle Body Fuel Injection Manifolds
sits ON the intake manifold
could have either one or multiple injectors
the injector sprays fuel into the area of maximum air velocity to ensure thorough atomization and ideal distribution.
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Sonic Tuning or Ram Tuning
Improves induction flow to increase cylinder charging and improves fuel distribution among the cylinders.
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One-piece manifolds
the plenum, intake passages and runners are built into one casting.
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Two-Piece Manifolds
consists of the upper intake manifold w/ a plenum and a lower intake manifold w/ individual runners.
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Variable Induction System
the primary (low-speed) runners longer & narrower for the low range RPM
the secondary (high-speed) runners are shorter & wider for high range RPM
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Port Fuel Injection can also be called what ? (2 names)
Multi-point or Multi-port Injection
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Construction of Port Fuel Injection ?
Individual injection nozzles for each cylinder are located in the ends of the intake manifold passages near the intake valves.
Only air flows through the manifold up to the location of the injectors.
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What does a Carburetor consist of ?
light-weight metal bodies that have one, two, three, or four barrels.
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Name four factors that can cause Vapour Lock:
1. High gasoline temperature due to engine overheating or high temperature weather
2. Low fuel-system pressure
3. Gasoline w/ too high a volatility
4. Low air pressure due to driving at high altitude
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Vapour Lock occurs ?
when the fuel bubbles form in the fuel lines, reducing fuel flow to the engine.
Partial vapour lock leans the air-fuel mixture and reduces engine power
Complete vapour lock causes an engine to stall, and makes restarting impossible until the bubbles in the fuel system disperse - usually when the fuel system is cools.
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V-Engines has its intake manifold where ?
between the cylinder banks
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Most In-Line engine has its intake manifold where ?
On the same side of the engine.
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High-performance In-Line engines have their two manifolds mounted on opposite sides of the cylinder head is called the ________ ?
Crossflow Design.
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Naturally Aspirated
uses atmospheric pressure to fill the cylinders w/ air.
Naturally aspirated engines operate at less than 100% volumetric efficiency.
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Pressurized Induction Systems
pressuring the air in the intake system allows more air to be forced into the cylinders which increases volumetric efficiency.
ex. Supercharger or Turbocharger
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Intercooling provides 3 benefits:
1. The density of air or air/fuel charge is increased by cooling, allowing a greater quantity of air/fuel to enter the combustion chambers, increasing power.
2. The heat stress on an engine is reduced, and valves, pistons and heads are cooler.
3. Less heat must be dissipated by the cooling system.
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Superchargers
driven from the crankshaft by a belt
supplies boost at all engine speeds
superchargers are positive displacement pumps
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A supercharger uses ___________ to drive the rotors.
a belt
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The turbine of a turbocharger is driven by ?
the outgoing exhaust gases
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What kind of pump is a Turbocharger ?
Centrifugal displacement pump - driven by the wasted exhaust heat.
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Exhaust Manifold Materials include ?
Cast Iron, Tubular Steel or Stainless Steel.
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Exhaust Systems perform several functions - which are ? (4 Points)
to provide a path to remove hot gases
to reduce noise
to deal with harmful emission concerns
and to discharge them safely away from the vehicle.
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Intake Manifold Heating is designed to
assist fuel vaporization at low temperatures.
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What is the purpose of the muffler ?
its purpose is to cool and reduce the pressure of the exhaust gas while quieting it's noise.
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Purpose of the resonator ?
can further reduce the sound level of the exhaust.
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Purpose of the Catalytic Converter ?
It converts the harmful by-products of combustion to relatively harmless gases
HC and CO to CO2 and H2O
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What are some factors tht can cause poor vaporization ?
Low mixture velocity or low fuel injection pressure
Insufficient fuel volatility
A cold manifold
Poor manifold design
Cold incoming air
Low manifold vacuum
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The throttle plate _________ ?
controls how much air is allowed into the engine.
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