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)

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.

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.

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

Reciprocating to rotary motion The pistons & crankshaft Image from: http://www.eng.iastate.edu/explorer/topics/car/engine.htm The connecting rod and the Crankshaft assembly change the reciprocating motion to a rotary one.

Piston, crankshaft, & fly wheel Image from: www.web-masters.com/ gms/crank_p.html

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

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.

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

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

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

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.

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

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

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

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

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

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

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

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