A two-stroke petrol engine completes the combustion cycle in two strokes of the piston rather than four as in a four-stroke engine. In a two-stroke engine, the intake and exhaust strokes are eliminated and ports instead of valves are used, with the exhaust gases driven out by the fresh fuel charge entering near the end of the power stroke. Everything a four-stroke engine does over two revolutions, a two-stroke engine accomplishes in one crankshaft revolution. Two-stroke engines are smaller, lighter, cheaper to produce but wear out faster and are less fuel efficient than four-stroke engines due to their greater pollution output.

1. SUB: INTERNAL COMBUSTION ENGINE
TOPIC: 2 stroke petrol engine
Shri S’ad Vidya Mandal Institute of
Technology
Prepared by: KADVA ZAKVAN

2. INTRODUCTION
 In 1878, Dugald-clerk, a british engineer introduced a cyle which
could be completed in two stroke of piston rather than four
strokes as is the case with the four stroke cycle engines. the
engines using this cycle were called two stroke cycle engines.
 In this engine suction and exhaust strokes are eliminated.
 Here, instead of valves, ports are used. The exhaust gases are
driven out from cylinder by the fresh charge of fuel entering the
cylinder nearly at the end of the working stroke.

3. 2 Stoke Engines
 Everything a 4 stroke engine
does in 2 revolutions a 2
stroke engine does in 1
revolution of the crankshaft.
How to identify 2 stroke
engine from outside:
• Exhaust port in center of
cylinder
• Small crankcase

4. 2 Stoke Engines part names
Combustion
chamber
Cylinder
Exhaust port
Intake port
Piston
Connecting
Rod
Crankshaft
Crankcase
Reed valve
Transfer port
Still uses a flywheel
(not shown)

5. WORKING OF 2 STROKE PETROL ENGINE:
FUEL INTAKE:
 Piston moves BDC to TDC
 Reed Valve Is sucked open
 Air/Fuel/Oil mixture sucked
into crankcase

6. COMPRESSION STROKE
 Piston moves TDC To BDC
 Reed Valve sealing
 Air/Fuel/Oil mixture is now
pressurized in crankcase
 Air/Fuel/Oil mixture squirts into
cylinder because of crankcase
compression

7. COMBUSTION & EXHAUST STROKE
 Air/Fuel/Oil mixture is
ignited in cylinder
 Reed valve close
 Every time the piston
reaches TDC, there is
another power stroke.

8. P-V diagram for 2 stroke petrole engine
Port timing diagram

9. Advantages of 2 stroke petlrol engine:
Smaller/lighter
Cheaper
Less friction
No oil to change
Quicker acceleration
Operate at different angles

10. Disadvantages of 2 stroke petlrol engine:
 The lack of a dedicated lubrication system means that the parts of a two-
stroke engine wear a lot faster.
 Two-stroke engines do not use fuel efficiently, so you would get fewer
miles per gallon.
 Two-stroke engines produce a lot of pollution -- so much, in fact, that it is
likely that you won't see them around too much longer.