1. Engine Dissection Project
Your team is dissecting a 3.5 HP single cylinder, 4 cycle engine, made by Briggs and Stratton in Milwaukee, Wisconsin
These engines are typically used in lawn mowers, snow blowers, go-carts, etc
(ref. 2, Used by permission of Briggs and Statton, ©1992, all rights reserved)

2. Engine Dissection Project
Start engine.
Disassemble engine.
Review parts and functions – Ask questions!
Reassemble engine.
Re-start engine.
Write individual report on how engine works.

3. 4 Cycle Process 4 1 2 3 Power Stroke Compression Stroke Exhaust Stroke
Exhaust Valve 4 1
Intake Valve 2 3
Exhaust
Manifold
Intake
Manifold
Spark
Plug
Cylinder
Piston
Connecting
Rod
Crank
Crankcase
Power Stroke
Fuel-air mixture burns,
increasing temperature
and pressure, expansion
of combustion gases
drives piston down. Both
valves closed - exhaust
valve opens near end
of stroke
Intake Stroke
Intake valve opens,
admitting fuel and air.
Exhaust valve closed
for most of stroke
Compression Stroke
Both valves closed,
Fuel/air mixture is
compressed by rising
piston. Spark ignites
mixture near end of
stroke.
Exhaust Stroke
Exhaust valve open,
exhaust products are
displaced from cylinder.
Intake valve opens
near end of stroke.

4. 1. Intake
2. Compression
3. Power
4. Exhaust

5. Reciprocating to rotary motion
The pistons & crankshaft
Image from:
The connecting rod and the Crankshaft assembly change the reciprocating motion to a rotary one.

6. Piston, crankshaft, & fly wheel Image from:
gms/crank_p.html

7. Piston Image from: www.rbracing-rsr.com/ 113orca.htm
darryl.hudson.home.mindspring.com/
ww.eng.iastate.edu/explorer/topics/car/engine.htm

8. Crankshaft
Image from :
toyotaperformance.com/crankshaft_kits.htm
Crankshaft for a 4 cylinder engine. Shining parts are bearings. The most left hand side is the ball bearing.

9. Several common types of car engine arrangement
Image from :
Automotive mechanics, 8th ed. By William H. Crouse
4 cylinder in-line
V-6
Flat-4 engine
6 cylinder in-line
V-8
Flat-6 engine

10. Power strokes in 2 crankshaft rotations
Why you need flywheel
Image from :
Automotive mechanics, 8th ed. By William H. Crouse
4 cylinder
6 cylinder
The force from the fuel combustion onto the piston is not a constant. The force onto the piston starts from some high pressure then decreases. In the figures here shows the force on the piston. The darker part means a larger force; the lighter part means a smaller force. You can see that with more cylinders, you’ll have more smooth out put. But still, you have variation in your output. In order to have a smooth output, you need flywheel.
8 cylinder
Output torque
Output torque
Output torque
time
time
time

11. Valve Mechanisms: How you get the right timing rocker valve push rod
Image from :
Automotive mechanics, 8th ed. By William H. Crouse
rocker
valve
push rod
piston
valve lifter
camshaft
cam
crankshaft
Timing marks

12. Lubrication
Image from :
Automotive mechanics, 8th ed. By William H. Crouse
Oil pump sucks the oil from the oil pan, and then distributes the oil to the moving parts. Ex: the piston, the cam, then return to the oil pan.

13. Venturi-type Carburetor
The carburetor of our engine
Fuel
Higher Pressure Outside Engine
Venturi
Choke
Throttle

14. How do engines work? Hint
How does the engine complete these Primary Functions?
Get started?
Suck in fuel?
Suck in air?
Mix air and fuel?
Compress the mixture?
Ignite the mixture (at the right time)?
Make the combusting gases do work?
Make the work available to somebody?
Exhaust the gases?
Shut off?
Think about the parts and processes involved for each.
Hint

15. How do engines work? Hint
How does the engine complete these Secondary Functions?
Stay lubricated?
Operate the valves at the right time?
Smooth out the power pulses?
Store the fuel?
Keep cool?
Make it easy to start?
Think about the parts and processes involved for each.
Hint

16. Some variations: Fuel Injection (electronic, multi-port)
Monitored Engine
Operating Conditions:
Manifold Pressure
Engine Speed
Air Temperature
Coolant Temperature
Acceleration
TRIGGER
COMPUTER
INJECTOR DRIVE UNIT
Pressure Regulator
Fuel
Filter
Fuel
Pump
50 psi typical
Why better than the carburetor?
Carburetor cars have troubles getting even fuel-air mixture into each cylinder. (because the Intake manifolds for each cylinder has different shape and length.)
For fuel injection, easier intake manifold design( only consider air flow). Better fuel-air mixture. And no big carburetor.
But why not all the cars with fuel injection? Cost! ( Need expensive sensors.)
Injectors
FUEL TANK

17. More variations: OHC( overhead camshaft):
DOHC, SOHC……
Image from :
Automotive mechanics, 8th ed. By William H. Crouse
Rocker
Valve spring
Valve lifter
Valve
Camshaft
Piston
Connecting rod
Crankshaft

18. More variations: VTEC( Variable valve timing and lift electronic control)

19. 2 Stroke Process (for comparison)
Compression
(ports closed)
Air Taken Into
Crankcase
Combustion
(ports closed)
Exhaust
(intake port closed)
Scavenging
and Intake
(ports open)
Air compressed in crankcase

20. Wankel Rotary Engine Smoother
Engine is continuously moving in one direction rather than changing direction like in piston engines.
Slower
Main moving parts move slower which increase the reliability of the engine.
Fewer Moving Parts
The rotary engine consists of three main moving parts while a piston engine contains at least 40 moving parts.
Challenges
Passing the US Emissions tests.
Manufacturing costs are higher.
Consumes more fuel.
This presentation created by former ENGR 100 students Sam Henry, Thomas Munsey, Grayson Deitering, Daniel Munro