GxT Ferret 63 DIAGNOSTIC ENGINE ANALYZER - Manual (Page 17)

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the sparks, the important ignition factor to check is the
time that the spark is exposed to the fuel mixture in each
cylinder.
For each spark, KV and the spark burn duration have a
trade-off relationship, where if one gets longer the other
must get shorter. This is why either measurement may
be used to evaluate ignition performance.
This analyzer excels in automatically measuring and
displaying spark burn durations for individual cylinders.
Because it measures each and every spark, both the
averages, the longest (Max) and the shortest (Min) burn
times are saved in analyzer memory and used for com-
parisons of the cylinders by the analyzer diagnostics as
well as by the user.
This is in contrast to the usual oscilloscope traces that
require recollection of the spark events to be from the
users memory after interpreting the readings from each
The No. 1 cylinder, in the first position of the waveform
has a gap in the spark plug wire which causes the short
burn time. The next two cylinders are normal. The last
cylinder has a fouled spark plug, as is seen by the much
more negative spark line slope.
shows on the display. Tha analyzer would also give two
diagnostic messages:
GAP Wide, Seq #1
PLUG foul? CAP track?
seq #4
The signal shown is of a current limited electronic ignition
on a 4 cylinder engine running at 2500 RPM.
BURN TIME READINGS and PRIMARY PARADE WAVEFORM
This figure illustrates the spark plug readings that this engine analyzer extracts from an ignition waveform, and then
cylinder's trace. Reading individual spark plug burn times
from an oscilloscope trace can be difficult because the
scale line is usually along the bottom of the screen and
the stacked raster pattern covers the whole screen. Ad-
ditionally, many scopes don't even have a millisecond
scale, and the screen sweep is only given in engine
degrees for setting or checking ignition contacts.
This analyzer is made to investigate the essential igni-
tion performance factors. It measures the coil's Ignition
Energy response to see that a strong spark is possible
without having to open a sparkwire. The analyzer reads
the total operating range of spark durations while the
engine is idling and accelerating. The numerical results
can be watched live as well as from the printed report to
see if long enough fuel igniting spark is delivered under
all conditions.
Slope
mSec
12 7 -20 18
0.8 1.6 1.5 2.0
SPARK 12 7 18 -20
Slope SPARK 0.8 1.6 1.5 2.0
mSec
See the BURN TIME key test explanation on the next
page.
COMPARING READINGS TO AN OSCILLOSCOPE
Ignition oscilloscopes are primarily designed for measuring kilovolts. While high voltages are the means which start