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F. Yellow Wire printed
– “Engine RPM Input”
This is not a signal to operate a tachometer, but the same signal from your
ignition system that operates a tachometer.
The engine RPM signal input on the yellow lead (pin 7) can be connected
to a digital tachometer output from an engine computer or the tachometer
output
from an MSD ignition or similar CDI (Capacitive Discharge Ignition)
system, but
NEVER to the coil outputs (coil negative stud) of a CDI system
like MSD.
For breaker points (or conventional electronic ignition systems such as GM
HEI, Ford Duraspark or TFI), it can be connected to the coil negative terminal.
For this configuration, add the supplied 47K Ohm resistor (yellow, violet,
orange,
and gold bands) to the yellow lead (pin 7) in-line with the tachometer
signal. The
correct setting will need to be set in the tuning software under
Settings>Speed
Sensor & Gearing.
For COP (Coil on Plug) ignition systems that do not have a conventional
tachometer output (such as later Mustang engines or 2007+ GM ECMs), one
of the coil trigger wires can be used, but the update rate will be slow. A better
approach for such
applications would be to use a tachometer adapter such as
the AutoMeter 9117.
Painless offers a tach driver for 2007-2014 GM ECMs,
part # 60150.
DO NOT run the engine RPM signal wire in the same wiring
harness as the
speed sensor as this can cause interference.
