MSD 8918 Tach Signal GMR Pickup Installation - Manual

MSD GMR Pickup
PN 8918/PN 89181
Parts Included:
1 - Giant Magnetoresistive Pickup, PN 8918/PN 89181
2 - Washers
1 - Brass Screw
1 1 - Parts Bag
The MSD GMR pickup can be used with inductive or capacitive ignition types to provide an rpm sig-
nal of 30% duration when the ignition coil fires. Two washers are provided with the pickup and must
be installed in one of two positions depending on the type of ignition driving the coil.
Note: For late model applications, it is recommended to have a wiring schematic of the vehicle’s
ignition system.
CAPACITIVE DISCHARGE IGNITIONS
For a CD Ignition such as an MSD, the two washers should be installed under the metal tab to pro-
vide a small air gap between the metal tab and the pickup sensor (Figure 1). Refer to note on Figure
2 for RPM Device programming.
INDUCTIVE COIL PER CYLINDER IGNITION
For an inductive ignition (mostly stock applications) the metal tabs must make contact, therefore no wash-
er is required. There should be no air gap between the metal tab and the pickup sensor (Figure 2). Refer
to note on Figure 3 for RPM Device programming.
DISTRIBUTORLESS COIL PACKS
On distributorless applications, the GMR pickup must be installed on the primary lead going to one
of the coils. If the pickup is installed on the main ignition +12v wire feeding more than one coil, the
pickup may not operate correctly at high speeds because of overlapping coil dwell current failing to
fall to zero current between coil operating cycles (Figure 3). Refer to note on Figure 3 for RPM Device
programming.
DIESEL INJECTOR
The GMR Pickup can easily be clipped to power fed wire of a Diesel Injector to provide a tach signal.
On a diesel, the washer must be installed under the screw head on top of the metal tab so there is
no air gap between the metal tab and the pickup sensor (Figure 4).
Note: If the GMR Pickup is attached directly to the individual injector the RPM device that is being
used must be programmed for single cylinder application. If the GMR Pickup is attached to
the main 12 volt feed to the injector harness, the RPM device must be programmed for 4, 6 or
8 cylinder depending on application.
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