AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 277)

Page 277 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
in the manifold.
Volumetric Efficiency
The intake system on a spark ignited engine, restricts the amount of air that an engine of a
given displacement can flow. The parameter used to measure the effectiveness of an engine's
induction process is the volumetric efficiency. It is defined as the volume flow rate of air into the
intake system divided by the rate at which volume is displaced by the piston.
Wasted Spark
A wasted spark is when in an ignition system in a four-stroke cycle internal combustion engine
spark plugs fire in pairs, on both the exhaust and compression strokes. The extra spark on the
exhaust stroke has no effect and is thus "wasted". This design is simpler than a conventional
ignition system, but the extra sparks reduce the lifespan of components (contact breaker, spark
plugs).
XY Plot
In data analysis, a plot of one variable versus another rather than time.