AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual - Manual (Page 286)

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© 2014 AEM Performance Electronics
Infinity User Manual
Combustion Chamber
The combustion chamber plays an important role in the amount of ignition timing that can be
used for the various operational phases of an engine. The most common type of combustion
chamber design used in contemporary engines is a four-valve/cylinder, pent roof chamber. There
are many other types of combustion chambers, such as a wedge, hemispherical, and canted
valve, to name a few. Ideally, it is best to initiate flame propagation at the geometric center of the
chamber. However, this is typically impossible to do because the spark plug is usually located at
the top or edge of the combustion chamber. The reason it is desirable to have the flame front
start at the geometric center of the combustion chamber is because there is less chance of auto
ignition of the mixture.
A pent roof combustion chamber places the spark plug near the center of the combustion
chamber. Wedge combustion chambers are the most sensitive to spark knock because of the
distance the flame front must travel within the bore prior to the power stroke.