Intro: Diesel Truck Mechanics Flashcards
Diesel Engine vs Gas Fueled Engines
Both Internal Combustion Engines.
Diesel engine has more hauling power, longer engine life, and much better fuel economy, operate at higher compression ratios, & the method of supplying & igniting the fuel makes it more efficient, also the grade and type of fuel diesel engines use makes it more efficient
Gasoline engine delivers usable torque through a much wider rpm range, runs quieter, & offers faster acceleration
ATA
American Trucking Association
ASE
Automotive Service Excellence
What are the 8 operating systems of a diesel powered vehicle?
Engine
Brake System
Suspension & Steering
Transmission
Driveline
Electrical & Electronic Systems
Heating & Air Conditioning
Tires & Wheels
Why is the engine important?
It is the Power Source of the vehicle. It is needed for all other components to function.
What brake system is used in midsized trucks and which system is used in large freight hauling trucks?
Hydraulic Brake System is used for midsized trucks.
Pneumatic Brake System is used for very heavy vehicles.
Explain how the Hydraulic Brake System Works:
The Hydraulic Brake System
supplies pressurized hydraulic fluid
to pistons
at each wheel
causing the brake pad
to rub against
the rotating disk
How is the hydraulic fluid pressurized?
By an engine driven pump
Between a hydraulic brake system and a pneumatic brake system, which one is more powerful?
Pneumatic Brake System
Does the Pneumatic Brake System control the truck or trailer brakes?
It controls Both!
How does the Pneumatic Brake System work?
How is PBS controlled?
The Drive System uses engine power to turn on the Air Compressor which then raises the Air Pressure which is then supplied to the Pneumatic Brake System & other components.
Pressurized Air.
It forces the pad against the rotating disk.
ABS
Antinlock Braking System
What vehicles are equipped with ABS?
Most diesel vehicles built after 1996
How is ABS controlled?
Electronically
Term: PBS
Term: HBS
Pneumatic Brake System
Hydraulic Brake System
What does ABS do?
Prevents wheels from locking up during sudden stops
Electronically monitors each individual wheel speed
Momentarily relieves braking force on any wheel that shows signs of locking up
What does the suspension and steering system do?
These systems allow the driver to properly control the vehicle on the road
Hydraulic
Pressurized Liquid
Pneumatic
Pressurized Air
What does the suspension system do?
Keeps the tires in contact with the road and prevents disturbance to passengers by absorbing road bumps.
What various load carrying & absorbing components does the suspension system incorporate?
Leaf spring, shock absorbers, rubber cushions, & air filled pneumatic components.
What does the steering system do?
Allows driver to control the direction of the vehicle.
What does the power steering system do?
It is a system powered by either a hydraulic or pneumatic system that makes it easier to steer vehicles.
What does the power steering system rely on to adjust the amount of power assistance needed?
Hydraulic valves or electronic control
Components of Automatic Transmission
No driver input
Hydraulic and electronic control systems determines when to shift gears and which gears to select
What is a Torque Converter?
A device that transmits power from the engine to an automatic transmission
What does the transmission system do?
Helps vehicle change speeds (imagine bike gears)
Standard Transmission
A.K.A manual; stick shift
4-20 gear selections
Relies on clutch to control the transfer of power from engine to transmission
What are the steps to using standard transmission ?
- Driver must disengage transfer of power from engine to the transmission by depressing a clutch pedal with their foot.
- Manually move gearshift lever to change transmissions internal gearing combination
- Restore power transfer connection been engine and transmission
What does the driveline system do and what components do it include?
Connect the engine to the wheels
Main transmission (sometimes), auxiliary power transmission, the difffrrentials, drive axes, & drive shafts
Tandem Drive System
Systems with 2 sets of rear drive wheels
Rear Wheel Drive
Most med sized and all large trucks
Rear wheels carry much of the weight
Larger, stronger, than FWD
FWD
Midsized & Comoact Vehicles
Engine & transmission is located at front over wheels
Uses this weight to provide better attraction for the front
AWD
A.K.A. 4WD
Better traction than RWD & FWD
Often used off-road
Light trucks, utility vehicles, heavy construction trucks, military veh
Differentials
Change direction of transmissions power input so it can be directly applied to rotating the drive wheels
Drive Axels
Directly turns the wheels
Drive Shafts
Transfers power from 1 driveline device to the next
Examples of Electrical and Electronic Systems
Battery, battery charging system, truck and trailer lighting circuits, starter system, windshield wiper, horn, radio, and other accessory circuits circuits, engine control system’s, ABS system, climate control system, pneumatic power circuit
What is Direct Current and where is it used?
Constant Source of Electrical Voltage
Same type of current that’s used to power cordless appliances or used on devices that run on batteries
How does vehicles optical systems operate?
All vehicles electrical systems operate on a direct current provided by the vehicle’s battery Through an array of harnesses
A _________ recharges the battery as tye engine is running
Separate electrical system
Heat is produced by _____
The running engine
Heating systems are used to do what?
Heating systems are used to keep a shut down engine warm when outside air temperatures are cold
Why are engines difficult to start in cold weather?
Because fuel in a diesel engine is ignited when it comes in contact with hot air
What system are the tires and wheels a part of
They are sometimes considered to be a part of the suspension system but they are considered to be a system all of their own
Internal conbustion engine means that
Fuel is burned inside the engine to produce power/mechanical energy
External conbustion engine means that
Fuel is burned outside of the engine
Ex: Steam engine/boiler burns fuel to produce steam and the steam is sent to the engine to produce power
Intake Stage
Air is pressurized and supplied outside of the cylinder by a Turbocharger and then forced into the cylinder where it is further pressurized
Compression Stage
Both intake and exhaust valve are closed
Piston rises and compresses air mixture that’s trapped in the combustion chamber
Due to compression the temp is then increased and as the piston reaches BDT C diesel fuel is injected through a nozzle
Power Stage
Measured fuel is sprayed into the hot air of the cylinder, igniting it, creating a combustion, which then presses the piston back down.
This motion is then transferred to the rod and crankshaft
Exhaust Stage
Stage #4
The burned exhaust gasses are released from the cylinder
Stage one starts again
What is one engine cycle?
How many cycles are completed per minute?
A complete run through of all 4 stages.
A typical crank shaft will complete 500 to 2100 revolutions every minute
What is the definition of pressure?
Pressure is the measure of how hard the contained air presses against the surface of the container in which it’s held.
What is a piston stroke?
A total distance that piston moves from the top of the cylinder to the bottom
What are the differences between a 2 stroke engine and a 4 stroke engine
4 stroke engine
1.Intake
2.compression
3. power
4. exhaust
Modern diesel engine trucks
Two stroke engine
1.Intake/compression
2.power/exhaust
Produces more power; found in older buses etc; not as fuel efficient; produces more pollution
How many valves and ports does a 4 stroke engine contain?
Contains 2 mechanical valves & 2 ports (exhaust & intake)
It also contains an injection nozzle & injection pump.
Injection Pump
Delivers correct amount of sufficiently pusherized fuel to the nozzle
Injector Nozzle
Engine part that introduces fuel into the chamber
What happens when the temperature is below 40ﾟ outside?
The cylinder temperature is unable to make the fuel even after compression so starting the fluid which is easier to ignite is introduced to the cylinder to begin the process in the read the temperature
In smaller vehicles a glow plug plug (small electronically powered heater) heats the air in the compression chamber prior to starting
A diesel engine’s _____________ system allows it to deliver as much power as possible while consuming as little fuel as possible
Computer control
The small space above the piston in which fuel is burned is called the ___________
Combustion chamber
When going uphill or downhill which gears are correct?
Uphill = Lower Gear
Downhill = Higher Gear
A heavy duty vehicles electrical system is normally rated at how many volts?
12 or 24 volts
What’s an example of a freight transporting diesel powered vehicle?
Train
What joins the tractor and the trailer?
The 5th wheel
Chassis Dynamometer
Evaluates engines overall performance while still installed in the vehicle.
What is a diesel engine?
An internal combustion engine that uses compression hear to ignite a fuel charge
In a diesel engine what is not mixed before entering the combustion chamber?
Fuel and air
In a diesel engine how is speed controlled?
By regulating the amount of fuel air mixture delivered to the cylinder.
What is the function of the governor in a diesel engine?
A governor is a device that senses engine speed and loads/changes fuel delivery accordingly.
No longer used.
Diesel fuel contains more _________ than gasoline
Heat energy (joules)
What problems are associated with diesel fuel at low temps?
Fuel starvation & Nonstart conditions
At lower temps the the wax begins to solidify into crystals which can block the fuel flow
Who was the 1st engineer to develop a compact reliable diesel fuel injection pump?
Robert Bosch
Compression Ratio
Comparison of the volume of air in a cylinder before compression with its volume after compression
Typical compression ratios used in a diesel engine range btwn 15:1 to 24:1
Diesel engine fuel is ignored simply by the ____
Heat generated from compression
What is the most common fuel system found on modern diesel engines
The high pressure common rail fuel injection system
2 & 4 stroke gasoline engines
vs
2 & 4 stroke diesel engines
All high horsepower gasoline engines are 4 stroke engines. 2 cycle gasoline engines are used for light duty applications such as power tools, lawn equipment, and boat motors.
In contrast
2 and 4 cycle diesel engines can be used in high horse power applications
What happens to the diesel fuel if the temperature increases more than a 100ﾟF?
The diesel fuel finds out and reduces the power output
Some of the technological developments made in the past 30 years include:
❏ Enhanced use of turbochargers and superchargers to increase power output and improve efficiency.
❏ Changes in combustion chamber, piston, and valve designs to increase fuel burning efficiency and power output.
❏ Advanced materials used to construct pistons, connecting rods, and other engine components.
Use of charge air coolers resulting in a 3%–5% improvement in fuel mileage and a reduced exhaust emissions.
❏ Improvements to unit fuel injectors and common rail injection systems, which are both capable of attaining higher injection pressures than earlier fuel injection systems.
❏ Matched intake and exhaust flow systems.
❏ Low-flow cooling systems and extended life cool-ants.
❏ Computerized fuel management systems and variable injection timing.
❏ Introduction of ultra-low sulfur diesel fuel and improved engine oil formulations to decrease emissions and improve efficiency.
❏ Incorporation of emission control technologies, such as exhaust gas recirculation systems, oxida-tion catalysts, particulate trap filters, and selective catalytic reduction systems—all designed to lower emissions and meet current environmental regulations
Stationary applications for diesel engines include
●electronic power generators
●industrial PTO (power takeoff) units
●motorized pumps
●cranes
●power shovels
