The four cycles of a gasoline engine are: 1) intake stroke, 2) compression stroke, 3) power stroke, and 4) exhaust stroke. During the intake stroke, air enters the cylinder. In the compression stroke, the piston compresses the air-fuel mixture. The power stroke occurs when the spark plug ignites the mixture, causing it to explode and push the piston. Finally, in the exhaust stroke, the spent gases are pushed out of the cylinder. Emissions from gasoline engines include hydrocarbons from unburned fuel, carbon monoxide from incomplete combustion, and nitrogen oxides produced at high temperatures. Creating the ideal air-fuel ratio and a complete combustion reaction are challenging.

1. By Adam Altenbern

2. 
The Four Cycles
1. Intake stroke-
piston lowers and
air from the intake
value enters the
cylinder.
2. Compression
stroke- the piston
raises and
compresses the air
gas mixture.
`
3. Power stroke-
accompanied by a
charge from the
spark plug, the
mixture explodes or
ignites.
4. Exhaust stroke- the
end result of the
whole reaction is
then pushed out of
the cylinder and out
the exhaust valve.
http://www.youtube.com/watch?v=wRIKJ6Av
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3. 
 The ideal mixture of every gallon of air and every
gallon gasoline is called the stoichiometric ratio
which is for every 1 gallon of gasoline there should
be 14.7 gallons of air. the ideal chemical equation is
as follows.
The Ideal mixture

4. 
 Hydrocarbon emissions are exactly what they sound like, the
emissions of hydrocarbons or in this case C3H8 called octane.
 this is caused by hydrocarbons not being combusted. Some
reasons include low engine temperature, broken sparkplug, the
quenching phenomena, or hydrocarbons being stuck in pores in
the cylinder wall.
Hydrocarbon Emissions

5. 
 In an ideal reaction carbon dioxide is released
instead of carbon monoxide.
 The main reason for this is if there is a lack of air and
this creates a partially burned emission.
Carbon monoxide
emission

6. 
 Oxides of nitrogen are expressed as NOx .
 There are many different oxides of nitrogen but nitric oxide
(NO) makes up the majority of 98% of the oxides of nitrogen
that are released.
 The main cause of this is high temperature and pressure
binding the nitrogen and oxygen together.
Oxides of Nitrogen

7. 
 Gasoline is a mixture of additives and octane. Octane or C3H8 is not
always used as just a straight-chained alkane. Octane is also formed
into isooctane (2,2,4-trimethyloctane) and 1-ethylbenzene.
 How the octane is created or which substituent is used gives it an
octane rating. The higher the octane rating the less likely the mixture
will prematurely combust.
Gasoline

8. 
 The difficulty in making a perfect combustion
reaction is difficult and you cannot take away one
unless you wish to add more of another.
The End Result

9. Citations
• "Emissions#1 - combustion chemistry." N.d. pdf file. toyota motor sales,
U.S.A.,
inc. All Rights Reserved.
http://www.autoshop101.com/forms/h55.pdf
• chemical makup and creation of gasoline:
Marshall, E. L., and Owen, K., eds. (1995). Critical Reports on Applied Chemistry,
Vol. 34: Motor Gasoline. Cambridge, U.K.: Royal Society of Chemistry.
Read more: http://www.chemistryexplained.com/Fe-
Ge/Gasoline.html#ixzz2QAG4KHT3
• "INTRODUCTION TO FUEL AND ENERGY." INTRODUCTION TO FUEL AND ENERGY.
N.p., n.d. Web. 28 Apr. 2013.
http://eyrie.shef.ac.uk/eee/cpe630/comfun1.html