Small Engines Final

cold cranking amps

(CCA)- the number of amps produced by the battery for 30 seconds at 0 degrees Fahrenheit while maintaining 1.2 volts per cell

746 watts =

1 horspower

governor spring rules

1 replace like for like 2 replace if damaged 3 never modify

Hp range

11-18hp

exhaust head of valve temp

1100-1450?

Diesel engine compression ratio

14:1 25:1

types

2 stroke and 4 stroke

Spark occurs when

20 degrees of crankshaft rotation before TDC Because it needs time to ignite

water boils at

212* F

% of energy required to compress charge before combustion

25% of the energy released during combustion

intake valve angle

30 degrees valve face 31 degree

% of engine energy is used

30%

exhaust valve stem temp

300-800

support service requires how many parts

35,000 parts

intake face temperature

400-700

exhaust valve angle

45 degrees face 46

average dealer age

45 years

safety can shouldn't exceed

5 gallons

usefull life

6 years for walk behinds and rear engine riding mowers 9 years for garden, snow throwers and tillers

head of intake valve temperature

600-800

Small gas engine ratio

6:1 8.5:1

lost to other places not usable bby the engine

70%

how many engines manfactured a year

8,000,000

outdoor power equipment industry

8.5Billion $

U.S AC Voltage

80 Hz

products

8CO2 + 9H2O + 47N2 +heat

exhaust face temperature

900-1450

intake valve stem temperature

<300

common types of valve guides

Aluminum Valve Guides: most common, predictable thermal expansion rate, good performance, low manufacturing cost Brass Valve Guides: greater resistance to wear, abrasive foreign particles, ability to embed abrasive foreign particles Sintered Iron Valve Guides: separate machined from powdered iron compound heated and compressed, highest quality, lubricating, resistance to wear

ANSI

American National Standards Institute Specialize in codes and standards helps identify industrial and public needs for national standards Is the National coordinator of voluntary standards activities Serves as an approval house and clearinghouse for consensus standards Is the US representative at ISO

API

American petroleum institute Primary trade association of US petroleum industry Provides public policy regarding the development of petroleum Also addresses enviro public safety issues

types of horsepower

Brake horsepower friction horsepower indicated horsepower

reactants

C8H18+ 12 1/2 O2+ 47 N2

Advantages of 2 stroke engine

Can be used in any position Light weight Simple Easier to clear out water

3 Ignition

Charge is ignited and rapidly oxidized to release heat

Class D

Combustable Metals star

Compression ratio

Comparison of volume of combustion chamber with piston at BDC VS TDC

Safety Rules

Don't operate engine in disclosed area Work in space with ample room Use approved spark plug tester to check for spark Do not have an open flame or smoke near flamable liquids Don't refuel engine while it's operating Be familiar w/ engine shutoff procedures for quick response in an emergency Do not operate an engine w/o a muffler never leave operating engine unattended

4 power

Hot expanding gasses force piston down Both valves closed to save power and prevent damages

Disads of 2 stroke

Increased fuel consumption Higher emmisions

LAT

Limited Angle Torque

Valve overlap

Most useful at higher speeds Happens during exhaust to bring in and push out air at the same time

NIOSH

National institute for occupational safety and health develop and revise recomended exposure limits for hazardous substances And work to reduce or eliminate these hazards More research

OSHA

Occupational safety and health administration established color code, Requires employees to have safe work environment More enforcement

Class A fire

Ordinary combustables: wood paper trash triangle

crankshaft parts

PTO, PTO journal (on side with gear), Rod Journal/crankpin journal, Magneto Journal, (all are bearing journals) counterweights, crankgear,

Class B

Petroleum products: flamable liquids, chemical square

PCV Valve

Positive Crankcase Vent Vents off extra pressure

Colors

Red: fire, danger, stop Orange: danger(ous parts of machine) (exposed pulleys, gears, rollers, cutting devices) Yellow: caution (power source of machinery, under repair, safety lines) purple: radiation green: first aid/safety Black/White/BW: traffic and housekeeping

SAE

Society of American Engineers Network of people who want to advance engineering Major source of information used in design of small engine powered systems Also have standardized method of testing engine output

5 exhaust

Spent gases are removed and released to atmosphere Exhaust valve open Piston going up

The higher the compression ratio

The more fuel efficient the engine

thermal conductivity

ability of a material to conduct and transfer heat

standard

accepted form or practice

sidedraft

air intake above fuel bowl and parallel to horizontal plane, used on crossover engines

downdraft

air intake above fuel bowl used in horizontal shaft engines

explain or sketch Bernoulli's principle

air moving through restriction increases in speed and creates a low pressure area which draws in fuel [ also the higher pressure area forces fuel up

air vane governor

aka pneumatic, senses engine speed by the amount of air coming off the flywheel, as engine speed decreases, the governor spring pulls the throttle open

wiper ring

aka scraper ring, napier ring, back up compression ring in the middle, provides consistent thickness of oil film to lubricate the running surface of the compression ring most have tapered angle face

DC Current

all sources have a positive and a negative terminal, flows in one direction, all points in circuit have polarity, common source is a battery

valve stem surface treatment purpose

allow reduction in valve stem to valve guide clearance and reduce friction related wear

WOT wide open throttle

allows maximum speed

importance of compression

allows more energy to be released when charge is ignited, heat is produced during compression from work applied by piston

Btu

amount of energy to raise 1 lb of water 1*F

friction horsepower

amount of power required to overcome internal friction of engines moving parts

reserve capacity

amount of time that a battery can produce 25 amps @ 80 degrees Fahrenheit.

brake horsepower

amount of useable power taken from engine

Hardfacing

application of material to an engine component to improve wear resistance from load, heat, and chemical corrosion

magnetism

atomic level force derived from the atomic structure and motion of certain orbiting electrons in a substance

temporary (soft) magnet

can only become magnetic in an external magnetic field

hydrocarbon emissions

caused by incomplete combustion, consist of methane, ethane, acetane, and other hydrocarbons not readily oxidized at normal engine temps

different ways to provide proper mixture for starting in cold weather

choke plate (restricts air flow creating lower pressure and draws up more fuel), primer system (rubber bulb depressed to force fuel into venturi), dry bulb primer system (rubber bulb filled with air connected to fuel bowl, allow atmospheric pressure into fuel bowl depressing it forces fuel into venturi), wet bulb primer system (rubber bulb filled with fuel, when depressed forces that fuel into venturi)

governor droop curve

combination of rpm decrease and maximum brake horsepower (BHP) curves

specific gravity

comparison of the mass of a given sample volume compared to an equal volume of water

circuit

complete path that controls the rate and direction of electron flow on which voltage is applied

Elliptical piston

conform to ever changing dimensions of cylinder bore

lpg gases that qualify and where they are used

consists of propane, propylene, butane, and butylene storage facilities, terminals, forklifts, other material handling equipment because of reduced emissions

crankshaft

converts linear motion of piston into rotary motion

piston ring rotation:

critical to engine durability

piston

cylinder slides back and forth in cylinder bore by forces from combustion process

bore of an engine

diameter of cylinder bore

Piston materials and requirments

die- or gravity-cast aluminum alloy must withstand pressure and tenp

lawn mowers need less precision

due to greater chance of hunting and surging for load variations

Class C

electrical circle

What happens to electrolytes as battery discharges

electrolyte loses sulfuric acid and increases the percentage of water resulting in a decrease in specific gravity

electricity

energy created by flow of electrons in a conductor

mechanical governor

engine speed is sensed by the movement of rotating flyweights in a mechanical governor system

alcohol in gasoline, characteristics, advantages, disadvantages, limitations

enhances octane rating, burns less btu than gas, has richer air fuel mixture, provides more oxygen which increases engine operation temp methanol (an alchohol additive) can deteriorate rubber fuel lines and carburetor components protective sealing, can cause extreme overheating, alcohol's affinity for water can cause water bubbles in fuel tank, cause problems in 2 stroke engines, remove lubricating qualities

cylinder head

fastened to the end of cylinder block farthest from crankshaft, keeps the cylinder sealed, helps cool the engine and holds the spark plug.

advantages of lithium ion batteries

faster charging time, contain less toxic materials, low self discharge rate(1.5% per month)

head gasket

filler material between cylinder block and cylinder head to seal combustion chamber

Current (I)

flow of electrons moving past a point in a circuit, can be alternating or direct, measured in amperes (A), {similar to measurement of water through a pipe gallons per minute}

Hertz

frequency is measured in this, is equal to one cycle per second

governed idle

function that allows engine to accept light to moderate loads w/o stalling the engine @ idle the governor spring applies no tension, so it does not open the throttle plate if the engine is placed under load can be fixed by adding a governed idle spring

a flamable liquid

has a flashpoint below 100 degree

parallel circuit

has two or more paths for current flow, Allows parts to be opened up and the other parts to still work

governor spring

helps pull throttle toward the WOT position

effects of change in altitude

higher altitude thinner air means smaller charge inside cylinder lower altiude thicker air means larger charge inside cylinder

study parts of crankcase

holds crankshaft in place and oil resevour

crankcase

houses and supports crankshaft, anything covering the crankshaft

effects of valve rotation

improved temp distribution, cleans valve interface causes surface wear

when throttle plate is moved toward WOT position, engine torque is

increased

updraft

intake opening below fuel bowl, used on engines with little room for air cleaner assemblies, fuel tanks, and PTO attachments

common clearances for intake and exhaust valves

intake: .002-.003 exhaust: .004-.005

interface angle

intentional deviation from a specification of two mating machine components to improve seating quality after a sufficient break-in period

inherent pressure

internal spring force that expands a piston ring based on the design and properties of the material used requires significant force needed to compress a piston ring to a smaller diameter

magnetic flux

invisible lines of force in a magnetic feild

tight droop

less stable speed control but results in more available power

stroke

linear distance piston travels in cylinder bore from top dead center to bottom dead center

lpg

liquefied petroleum gas

integrally machined valve seat

machined portion of cylinder block, often used for intake valves

governor purpose

maintain engine speed regardless of applied load and conditions

engine governor

maintains engine speed by modifying air fuel mixture in carbuerator

conductor

material that allows the free flow of electrons

valve seat function

mates with valve face to seal combustion chamber/ removes heat from valves

electric dynamometer

measure brake horsepower by converting mechanical energy into electrical energy

eddy current dynamometer

measure engine torque using load produced by magnetic field

throw

measurement from center of crankshaft to the center of the crankpin journal, which is used to determine the stroke of the engine

water dynamometer

measures engine torque using load produced by a water pump

test tool

measures the condition or operation of engine component or system

prony brake

measuring engine torque using brake that exerts preasure on spring scale

carburetor

mixes air fuel mixture

function of the carburetor

mixes and provides required air fuel mixture to combustion chamber based on engine operating speed and load, air is drawn through carburetor as piston moves down and creates low pressure area

electrolyte

mixture of water and sulfuric acid used in lead acid battery

hydrocarbon molecule

molecule held loosely together by bond between hydrogen and carbon atoms, occurs naturally in all fossil fuels

speed sensing device

monitors engine speed and functions to maintain slowest possible engine speed

multiple barrel

more than one venturi, may have common or shared intake, used on bigger engines

gasoline as a fuel source

most common fuel, was originally undesirable by product, was used for lamp fuel and cleaning agent

AC Current

most common, produced by generator (rotating magnet through wire coil) , current changes directions

normal atmospheric air

mostly nitrogen and oxygen

flywheel

mounted at end of crankshaft provides inertia for the engine swings magnet around to build up charge for spark plug cooling fins to cirulate air

piston function

movable end of combustion chamber, creates compression

camshaft

moves and times tappets and valves

radiator

multi-channeled container allows air to pass around the channels to remove heat from liquid within

4 types of carburetor designs and common uses

multiple barrel, sidedraft, downdraft, updraft

piston ring twist:

negative twist in piston ring, creates a seal against the ring land during non combustion strokes

all 3 nitrous oxide compounds that are commonly produced

nitric oxide, nitrogen dioxide, and dinitrogen monoxide

Frequency

number of complete electrical cycles per second (cps)

antiknock index and how it relates to octane numbers

numerical value assigned to gasoline that indicates the ability to eliminate knocking and pinging in an engine, octane quality is indicated by the anti knock index research octane number is octane number that impacts engine knock at low speeds, market octane number at high speeds

lambda excess air factor

numerical value assigned to represent the stoichiometric ratio of atmospheric air to any hydrocarbon fuel small engines usually .6-.8

octane rating

octane is ability to resist engine knock and ping

flo-jet

older style, uses float bowl

valves

opened by tappets and camshaft intake brings in air fuel mixture exhaust releases exhaust gases

resistance

opposition to flow of electrons, measured in ohms

main (high speed) circuit

path from fuel bowl to emulsion tube created by fixed orifice jet in carburetor, helps control engine speed, increases engine performance with better control of fuel entering air stream

1 intake

piston moves down drawing air fuel mixture into combustion chamber, intake valve open

2 Compression

piston moves up compressing the air, both valves closed

Valve Interface

point of contact between valve face and valve seat

low volatility

poor cold weather operation

high volatility

poor hot weather operation

applied pressure

pressure applied from combustion gases to piston ring causing it to expand

vapor pressure

pressure exerted above the surface of the liquid

piston ring rotation

prevents any compression gasses or oil from entering ring land. and wear, maintains acceptable exhaust gas emmission

honing

process using hone with rigid carborundum stones rotated in cylinder bore to remove small surface irregularities and any glazing

adiabatic process

process where heat is derived from process itself heat is produced by work of piston, the increase in temp is proportional to quantity of work applied to compress the charge.

volatility

propensity of a liquid to become a vapor, all liquids have a certain measurable volatility based on the liquid and ambient temperature

valve guide function

provide consistent clearance between itself and the valve stem regardless of operating conditions and removes heat from valve

33000 jobs

provided

Barrel Shape piston

provides smoother transition during direction changes of piston, the piston roll into the cylinder wall when changing direction at the end of a stroke reduces noise, spreads force of directional change across a greater surface, and reduces side loading on the piston skirt

compression ratio

ratio of volume at BDC to volume at TDC small gas engines: 6:1 to 8.5:1

why lead acid batteries need to be recharged

reaction can not continue indefinitely, recharging drives the reaction backwards to store up electrons

bearings

reduce friction , maintain clearance between stationary and rotating components of engine

when throttle plate is moved toward WOT position, level torque is

reduced

Code

regulation or minimum requirment

governed idle spring

removes lost motion between the governor spring and governor linkage to improve governor sensitivity @ low rpm

how lithium ion batteries are used

replace lead acids in vehicular applications

piston ring dynamics

requires presence of oil film between piston ring running surface and the cylinder wall, piston rings should not touch the wall,

Valve Seat Insert

separate machined component pressed into the cylinder block, made from sintered iron

piston windows

series of small holes machined into oil ring groove surface of the piston

tappets/valve lifters

sit under the valves to move them

idle circuit

small hole in throttle plate, allows fuel mixture past throttle plate to prevent stalling at low speeds

Taper piston

smallest diameter of the taper at the piston head compensates for thermal expansion and growth

PPE

snug denim coveralls w/ freedom of movement convenient access pockets that don't snag, long hair secured, jewelry removed, safety glasses, face sheilds, goggles

stoichiometric ratio

specific air-fuel ratio of atmospheric air to fuel at which the most efficient and complete combustion occurs

detonation

spontaneous combustion of significant portion of charge before the spark induced flame front reaches it aka knocking, spark knock pinging causes pressure difference, then shock waves

wide droop

stable speed control but results in less available power

three functions of electrical system

starting engine, spark for ignition at proper time, battery charging system

magneto

stationary magnet that builds up charge for the sparkplug

permanent (hard) magnet

stays magnetic even after magnetizing force is gone

indicated horsepower

sum of brake and friction horsepower total power produced in engine cylinder

engine block

supports and helps maintain allignment of internal and external components/ keeps parts alligned

electronic governor

system that uses a LAT motor in place of the governor spring and speed sensing device provides greater sensitivity and control of engine speed than a mechanical governor

measurement from center of crankshaft to center of crankpin journal

throw

Hazard Diamond

top red: fire hazard right yellow: reactivity bottom white: specific hazard left blue: health hazard

compression ring

top ring, most exposed, transfers combustion chamber heat from piston to cylinder wall

piston rings

top: compression ring- seals combustion chamber middle: wiper ring- further seal and wipe cylinder walls botton: oil ring- wipe cylinder walls

carbon monoxide (char, reason it is produced, etc.)

toxic gas produced by incomplete combustion of gasoline or other HC-based fuels

connecting rod

transfers motion from piston to crankshaft and functions as lever arm

series circuit

two or more components connected so there is only one path for current flow

oil ring

two thin rails, holes cut in the radial center of the ring allow flow of excess oil back to the oil reservoir, highest inherent pressure

pre-ignition

undesirable engine condition, occurs when small portion of combustion chamber component or a particle in the combustion chamber becomes excessively heated and ignites the charge as it enters the combustion chamber

Hysteresis

undesirable motion of governor system components caused by engine vibration and governor system friction characteristics Related to wave physics: resonance, oscillation, etc

Hunting

undesirable quick changing of engine rpm when set at desired speed

Surging

undesirable slow changing of engine rpm in a cyclical pattern when the engine is set at a desired speed

Maverick Air

undesirable unaccounted for air entering engine through leaks caused by worn engine components decreases engine performance and increases exhaust gas temp

diesel engines

use injection pump to deliver pressurized fuel to cylinder at precise intervals heat from compression ignites fuel mixture

pulsa-jet

uses a pump to lift fuel from fuel tank to fuel cup (a resevoir high in fuel tank), more efficient than vacu-jet

magnetron ignition system

uses electrical components in place of breaker point and condenser, provide greater efficiency, and reliability

vacu-jet

uses fuel tank as very large fuel bowl with single pickup tube to fuel supply

breaker point ignition

uses mechanical switch to control timing of ignition, uses induction produced in ignition coil to cause a spark to ignite the charge, point plunger prevents movable points from touching fixed contact surface

induction

using magnetic field to create voltage and current conductor passes through magnetic field

components involved

valves, valve guides, valve seats, pistons, piston rings, and cylinder bore, head gasket, valve train

generators need

very precise speed control

volts (v)

voltage is measured in volts, volt is the unit of measure for electrical pressure difference between two points in a conductor or device

charge

volume of compressed air fuel mixture trapped inside combustion chamber ready for ignition

displacement

volume of stroke =strokeX.5(bore)^2Xpi

dynamometer types

water, electrical, eddy current, prony brake dynamometers test horsepower

preignition

when parts of the combustion chamber become heated and ignite the fuel mixture as it enters the chamber decreases problems, makes noises

WOT

wide open throttle

how is specific gravity checked, what does it indicate?

with a hydrometer, a decrease in specific gravity means a discharged battery