Submitted by
Karthik .S.N

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HEMI engines
INTRODUCTION
Engines are the major components of any automobile. A user of an automobile wants to get maximum power output from the engine, at the same time, not sacrificing fuel efficiency. The design of an engine is very important. One of the most important parts of engine design is the design of the combustion chamber. Different types of combustion chamber heads are being used at present.
One type of chamber head is the hemispherical head. The hemispherical head design enables the user to extract more power from the engine. The engines using hemispherical heads are known as HEMI engines.Modern HEMI engines are using various developments that have come up in the recent past. This has enabled these engines to provide the user with additional advantages apart from serving its major purpose, ie, supplying more power.
Engine is the basic component of any automobile. Combustion engines may be divided into two general classes - internal combustion engines and external combustion engines.In the external combustion engines, a working fluid is utilized to transfer some of the heat of combustion to that portion of the engine wherein this heat is transformed into mechanical energy.
The internal combustion engine inducts air from the atmosphere and the combustion of fuel and air occurs in or near that portion of the engine, which converts heat to mechanical energy. Internal combustion engines may be further classified into reciprocating engines and non-reciprocating engines. Internal combustion engines may also be divided as spark ignition engines and compression ignition engines.
Spark ignition engines may work in a two-stroke cycle or a four-stroke cycle. The four strokes involved are
1) Intake stroke
2) Compression stroke
3) Power stroke
4) Exhaust stroke
The design of the combustion chamber for a spark ignition engine has an important influence on the engine performance and its knocking characteristics. The design involves the shape of the combustion chamber, the location of the spark plug, and the location of the inlet and exhaust valves. The important requirements of a spark ignition engine combustion chamber are to provide higher power output with minimum octane requirement, high thermal efficiency and smooth engine operation.
BASIC DESIGN
The HEMI engine was first developed in 1951 by the Chrysler Corporation. The advantage of HEMI engine over other engines of the time was that it produced more power. The reason for this was the efficiency of the combustion chamber.