Fuel And Oil - Shindaiwa 300 Service Manual

Section
14 Appendix
Fuel and Oil
Gasoline
What you need to
knowabout
today's motor
fuels. "
o
ATTENTION!
Under certain conditions, so-called
"oxygenated" motor fuels can raise
engine combustio n chambe r tempera­
tures beyond acc eptabl e limits, and can
lead to major eng ine failu
re l
Oxygenated Fuel
Under the provisions of the Federal Cle an Air
act of 1990, gasoline sol d in man y "non ­
attain ment" areas is now blended with an
oxygen-beari ng compound on at leas t a
seasonal bas is.
The most common oxygenates in use
contain either alcoho l or an ethe r ad ditlve
Since both alcohol and ether contain oxygen,
an engi ne bu rning either compound will have
a hotter rate of combust ion from the leaner air­
fuel rat io.
Some states require th at the use of oxygen­
ates be pos ted at the pump. Elhanol alco hol is
a comm onl y used oxyge nate , and may
conta in as much 35% oxygen . Ether-based
compounds may conta in as much as 18%
oxygen and are often marketed as MTBE ,
TAME, or ETBE .
IMPORTANT!
Eth er-based compounds contain ap prox l­
mately one-half the oxygen of ethanol, and
are usuall y less damag ing to a two-cycle
engi ne!
Octane Rating
Igniting a fuel within a cy li nder causes a rap id
expansion of burning gasses . This expansion
is what forces the pi ston to move down lile
cylinder an d rotate the cranksha ft.
Fuel wit h a low octane ra ti ng can ignite
violen tly (detona te) in a high compression
engine, however, and may produce cy li nder
pressures 2 to 3 times higher th an en gme
desig n limitations . Su ch pressures can have a
"hammering" effect on pistons and bear ings,
and can shor ten an eng ine's performance life
si gn ificantly.
Higher octane fuels are designed to burn
longer, producing a stead y and con trolled
increa se in combustion ch amber pressures.
For max imum pe rformance and eng ine life,
Shindaiwa cha in saws require a fUel ilh an
octane ral in g 01 at least 87 .
IMPORTANT!
Eth ano l will increase luel octane ratin g by 2
to 3 point s and is often blended wilh
gasol ine as an octane enh ncer or
"booster".
Volatility
For easy star ti ng and maximurn en gine
perfo rm ance , gasol ine must remain in a li qul d
state only until it enters Ihe carb uretor ventu ri.
Gasoline evapo ra tes more rap idly in a
warm c li mate than in a coo l cli mate, an d a
high-volatile gasoline viii cause pe rformance
prob lems il il vaporizes in the engine's
f
el
lines or carburetor.
The op poslte is true In cool weath er. A low­
vola tile fu el can "pud dle" in ¡he combustion
chamber, an d may cause an eng ine to be
hard to start.
IIVIPORTANT!
Non-seasonal gaso line can cau se hard
starting due lo either vapor-Iock or pud­
dling I Always purchase fresh gasollne from
a name-b ran d dealer!
Alcohol and Water
Condensation can produce water droplets on
the in ner wall s 01 fu el lanks and olher storage
co ntainers. Thes e droplets can be read ily
ab sorbed by alcohol present in (he fuel .
• If the alcoho l in vo lve d has been ble nded
with g asolille , th is new al cohol-water
mixt ure is pro e to p hase separate and
fo rm a separate and highly corro sive layer
al the bottom of the fuel lan k.
• If this layer is draw n
In
throu gh an engine's
fuel filler, the en gine will burn a highly
oxygenated lean fuel mi xture canlai in g
liltle or no lubri catin g oil
l
IIVIPORTANT!
Al coh ol blended with gasoline can absorb
water, and may "phase separate" to form a
water-alcohol mixture that can shorten
en gine Ilfe dra sticallyl
Storage
Gaso lin e is a compl ex b lend 01 many different
compounds , so me 01 wh ich may degrade
durin g storage.
Old or "stale " gasoilne in an eng i e 's fuel
system can attack or deteriorate fu el llne s,
carbure tor diaphragms , and rela ed fuel
system com ponents .
134
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Sh.ndaiwa
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