Fuel Induction Ignition And Starting Systems Flashcards
Out of these fuels (natural gas, gasoline, propane and diesel) which has the highest heat value?
Diesel
What is a BTU and what does it stand for?
- BTU is the measure of heat content of fuel. The amount of heat required to heat 1lb of a liquid by 1F
- British Thermal Unit
What is the metric version of BTU?
- The Calorie. Its is the amount of heat needed to heat 1g of a liquid by 1C
Are high Octane fuels faster burning or slower? What does this mean for car parts
- Slower
- High octane is better for car parts. There is a softer piston push.
Are higher temps of air and high compressions ratios beneficial with diesel engines?
- Yes
Are higher temps of air and higher compression ratios beneficial to spark plugs?
- No, this can lead to pre-ignition, detonation or both.
The _______ the octane number, the more the fuel can resist self-ignition.
Higher
Which has lower compression ratios CI-type of SI-type?
- SI-type
Is fuel premixed with air before compression and ignited in SI-type systems
Yes
What type of ignition is this?
What is happening?
- Pre-ignition
- Two flames are caused in the combustion chamber. One from the spark plug another from a hot spot else where. The flame fronts cause a fast burn which leads to abnormal pressure rise causing piston knocking.
What type of ignition is this?
- Detonation
Explain what detonation is?
Process where after spark plug ignition the flame causes the opposite sides air fuel mixture to compress even more and ignite prematurely. With these two flames fronts colliding excessive pressure builds in the cylinder causing knocking.
What must be done to gasoline fuel before it enters the engine cylinders?
What methods are used to do this?
- Must be metered, atomized and mixed with air.
- Carburetor and Electronic Fuel Injection
What are the four basic parts of a Carburetor?
- Carburator
- Fuel Pump
- Fuel Tank
- Filter
What is this? Label the picture.
- Simple Carburetor
What is a Venturi?
A restriction in the air horn (air intake) that creates a low pressure area (vacuum) in the carburetor sucking and mixing gas.
What is the Throttle?
A butterfly valve that is the speed control mechanism for the engine. Controls the amount of air and fuel that enters the cylinders.
What is the “Choke”?
Is a valve before the venturi or throttle that blocks the air horn (air supply tube) to increase the amount of fuel that enters the cylinders.
What is an Expansion Tank?
It is similar to an accumulator but for fuel lines on engines. It is a spare resivour of fuel incase there is a moment where no fuel is delivered down the line.
Is propane odourless and colourless?
Is air heavier?
- Yes, the egg smell is added to it later.
- No, propane is 1 1/2 times heavier then air.
At what temperature is propane a liquid? How much does it expand?
- At - 42 C or -44 F or below
- 270 times when changing from liquid to gas
What is the mandated capacity percent for propane in propane storage tanks?
And why?
- 80%
- Because of the large expansion rate
Why are CI systems high compression?
- Because disel fuel needs a high temperature to ignite (has a high BTU value). And the higher the compression the hotter air gets which then ignities the fuel.
Why is there a high pressure fuel injection system in diesel engines?
Because air is injected into the cylinder first then compressed to cause heat. Then the fuel is injected in and without the high pressure it would not pentrate the air, mix and atomize inside the cylinder.
Where does diesel fuel mix with air in a CI engine?
In the combustion chamber. Which is different then a gasoline engine.
What can be done to help a cold CI engine start.
Give the fuel some starting aid (chemical additive). This gives the engine some additional heat upon compression.
What are the two Fuel Injection System types?
- Mechanical Injection/ Mechanical Control
- Mechanical Injection/ Electrical Control
Name some Mechanical Injection/Mechanical Control subsystem types:
- Distribution Fuel Injection
- Inline Fuel Injection
- Unit Fuel Injection
What type of injection system is this?
Name all the parts.
Inline Fuel Injection
What is a Distributor Fuel Injection System?
Where is it used?
A Mechanical Injection/ Mechanical Controlled Fuel injection System that uses one high pressure pumping plunger that distributes and pumps fuel to a distribution head which is then diverted to each of the injector nozzles at each cylinder.
- Many small automotive diesel engines.
What is a Inline Fuel Injection Pump System?
A self-contained unit that has its own cam and plunger for each cylinder. Each one of these plungers (pumps) has a high-pressure line that goes to the individual cylinder injector.
What is this? Name the parts.
- Inline Injection Pump System and Metering Rack
What is the port and helix metering method?
For Inline Injection Pumps. Each plunger pump is geared to a rack that is controlled by the governor. The position of the governor linkage adjusts the rack, which then rotates the plumgers in their bore. This changes the position of the plunger helix port for when fuel is delivered to the injector.
What type of Injection System is this?
Unit Fuel Injection
What is a Unit Fuel Injector similar to? What is the difference?
- Inline Injector System
- The injector pump is mounted in the head of the engine. The engine cam drives the pumping element through a pushrod mechanism. as with the inline method, the metering is done using a port and helix method with the rack that is attached to the governor by a set of linkages.
How do you depressurize a Fuel System for a engine? What happens if you cannot disconnect the pump?
- Isolate the pump and supply and run the engine until it stalls. Then crank the engine for 20 to 30 seconds to clear the remaining pressure.
- Bleed the fuel pressure off into a cloth wrapped around the pressure test port or at a flexible fuel line disconnect.
What is the “Induction System” responsable for in an engine?
- Cleans intake air
- Ensure sufficant quantity of air for combistion
- Brings air to correct temp
- Aids cooling of valves and other internal parts by use air.
What happens if air is too hot for Induction Systems? What about too cold?
- The power drops off
- Too cold, lead to a drop in compression temp which results in poor fuel ignition and thermal shock to the engine.