4. 4
Gasoline Engine
Valve Overlap: The duration (10o
+ 20o = 30o) when both the inlet and
exhaust valves remain open is called
valve overlap.
Spark Advance: The ignition is
initiated 20 – 30o before TDC. This
is called spark advance.
5. Valve timing for two stroke SI engine
Valve timing diagram
Two Stroke timing diagrams: timing diagrams are
self-explanatory
5
6. SUPERCHARGING
The power and efficiency of an internal
combusting engine can be increased with the use
of an air compression device such as a
supercharger or turbocharger. Increasing the
pressure and density of the inlet air will allow
additional fuel to be induced into the cylinder,
increasing the power produced by the engine.
Superchargers and turbochargers are used
extensively on a wide range of diesel engines,
since they are not knock limited. SI engines are
knock & compressor pressure limitation. 6
8. Looking at the difference between the
two the supercharger will take its
power from the crankshaft whereas
the turbocharger will draw power
from exhaust gases that result from
combustion. Superchargers will spin
with speeds up to 50,000 RPM.
The turbocharger is not connected to
the engine and can spin much
faster. 8
