The document discusses powertrain systems for vehicles. It covers calculating the necessary engine power to move a vehicle based on factors like weight, speed, transmission losses, and overcoming slopes. Key points covered include selecting the appropriate engine size based on the work needs and efficiency, basic engine components, diesel engine systems, and combustion stages. Formulas are provided to calculate engine power needed based on road resistance and available traction. An example calculation is given to determine the necessary engine power for a specific off-road vehicle scenario.

1. Powertrain system
Vehicle Engineering

2. 1. Engine power

3. Learning outcome / session
achievement
At the end of this class the students must be
able to:
• Calculate the necessary power of the engine
to move a car or truck

4. 1.1 Selecting correct engine
One of the first things to evaluate is the amount of
energy or torque the engine can generate;
matching the size to the work needs is critical. The
size and weight of the engine will affect vehicle
performance.

5. 1.1 Selecting correct engine
Fuel efficiency of the unit is also important, as well
as the cost depending on the application

6. • Top dead center (T.D.C.): In a reciprocating engine the piston
moves to and fro motion in the cylinder. When the piston moves
upper direction in the cylinder, a point at which the piston comes to
rest or change its direction known as top dead center. It is situated
at top end of cylinder.
• Bottom dead center (B.D.C.): When the piston moves in
downward direction, a point at which the piston come to rest or
change its direction known as bottom dead center. It is situated in
bottom side of cylinder.
Basic definitions

7. • Stroke (L): The maximum distance travel by the piston in single direction is known as
stroke. It is the distance between top dead center and bottom dead center.
• Bore (b): The inner diameter of cylinder known as bore of cylinder.
• Maximum or total volume of cylinder (Vtotal): It is the volume of cylinder when the
piston is at bottom dead center. Generally, it is measure in centimeter cube (c.c.).
• Minimum or clearance volume of cylinder (Vclearance): It is the volume of
cylinder when the piston is at top dead center.
• Swept or displace volume (Vswept): It is the volume which swept by the piston. The
difference between total volume and clearance volume is known as swept volume.
Swept volume = Total volume – Clearance volume
Basic definitions

8. Basic definitions
• Compression ratio: The ratio of maximum volume to minimum volume of cylinder is known as the
compression ratio. It is 8 to 12 for spark ignition engine and 12 to 24 for compression ignition engine.
Compression ratio = Total volume / Clearance volume
• Ignition delay: It is the time interval between the ignition start (spark plug start in S.I. engine and
inject fuel in C.I. engine) and the actual combustion starts.
• Stroke bore ratio: Stroke bore ratio is the ratio of bore (diameter of cylinder) to length of stroke. It is
generally equal to one for small engine and less than one for large engine.
Stroke bore ratio = inner diameter of cylinder / length of stroke
• Mean effective pressure: The average pressure acting upon the piston is known as mean effective
pressure. It is given by the ratio of the work done by the engine to the total volume of engine.
Mean effective pressure = Work done by engine / Total volume of cylinder

9. Difference between:

10. Difference between:
Speed vs velocity
https://www.youtube.com/watch?v=O22zcaELpaA

11. Diesel engine components
• Block: The modern diesel engine starts with
a block, containing all the parts for the basic
internal combustion process. There is an
open space in the block for each cylinder,
where the combustion process takes place.

12. Diesel engine components
• Crankshaft: The first piece we need is the
crankshaft. This is the piece that converts
the linear motion created by combustion into
rotational motion.

13. Diesel engine components
• Connecting rods: Next we need something to
connect the crankshaft to the cylinder and
carry the force of the combustion to it. These
are the connecting rods.

14. Diesel engine components
• Pistons: Each connecting rod attaches to a
piston at the top. The pistons create the
bottom of the combustion chamber and
move up and down in the cylinder during
operation.

15. Diesel engine components
• Cylinder head: At the top of the block is the cylinder
head. This closes the top of the combustion cylinder
to contain the force of the combustion event. The
head can be one unit covering all the cylinders or
multiples with each covering a portion of the
cylinders, depending on the design.

16. Diesel engine components
• Valves: Now that the cylinder is closed off, the
engine needs valves to allow the combustion
gases to flow out and fresh air to flow in during
the process. There are usually two valves for
exhaust and two for intake air on each cylinder.

17. Diesel engine components
• Fuel Injectors: The component for getting fuel
inside the cylinder is probably the most complex
part of the combustion system. Fuel injectors
spray fuel into the top of the cylinder in very
precise patterns with highly controlled timing.

18. Diesel engine components
• Camshaft: Most engines still rely on a mechanical system to open
and close the valves, and some still use mechanical actuation
(instead of electrical) for the fuel injection. The camshaft’s
revolutions control the timing of each event through the geometry
and placement of the lobes on the shaft.
• Cylinders: Work together to produce a combustion event with the
engine block and piston.

19. • To operate effectively and safely, the engine
must continuously deliver air, fuel and
lubrication to the cylinders. In addition,
engine emissions, created as by-products of
combustion, must be treated to meet global
environmental standards.
Diesel Engine Technology

20. Diesel engine
systems
Air
Fuel

21. Diesel engine
systems
Lubrication
Cooling
Filtration

22. Combustion stages

25. Fuente: https://motorgiga.com

26. Fuente: https://motorgiga.com

27. Fuente: https://motorgiga.com

28. Fuente: https://motorgiga.com

29. Calculate the necessary engine’s
power Wm
Wm = Wr + Wa
Wm= (Rr+Ra)*speed
Wm=kgm/s o CV
1 kgm/s = 0.01333 CV

30. Exercise:
• Calculation of power required Wm to move the
vehicle:
For a vehicle in normal work off the road, with
maximum speed of 50km/h in sand at 95% of the
maximum power of the engine.
Remember the losses by transmission. What
would happen if I want to overcome a slope at 40
km / h? What would be the power of the engine?

31. Bibliografía
• Blundell, M. and Harty, D (2004). The Multibody Systems Approach to Vehicle
Dynamics. Elsevier Butterworth-Heinemann. Oxford - UK.
• Cascajosa, M (2005). Ingeniería de vehículos, sistemas y cálculos. Alfaomega.
México.
• Gillespie, T (1992). Fundamentals of vehicle dynamics. SAE International.