D
ATA
M
AXX
E
NGINE
RPM
Overview:
The
D
ATA
M
AXX
can read your engine rpm by taking a signal from a tachometer or the ignition system. It
also has a separate channel dedicated to reading rpm from magnetos.
Installation:
Electric Tachometer:
If you have an electronic or mechanical tachometer, the easiest method to obtain engine rpm would be
to simply tap into the tachometers signal wire. On most tachometer manufacturers the signal wire
should be the green one. Simply plug this signal wire into the ‘RPM ENG’ terminal (id #32).
Ignition Systems:
Many CDI, electronic, and computer ignitions (such as MSD) have a dedicated tachometer output.
Simply plug this signal wire into the ‘RPM ENG’ terminal (id #32).
Ignition System with External Coils:
If your ignition system does not have an electric tachometer or dedicated tachometer output, but does
have an external coil, then that coil will have one high tension spark plug type wire (typically plugged
into the top center) and two low tension smaller wires (typically screwed onto posts near the top). One
of the two low tension wires will be a suitable rpm signal. If the two wires or terminals are labeled “+”
and “-“, use the “-“ side for your rpm signal. Otherwise choose one side arbitrarily. It is safe to connect
to the wrong one and you’ll realize you’ve done this if you get a very poor rpm reading. In that case,
try the other terminals.
Magneto Ignitions:
We recommend using a mag tach adapter that will accept the noisy magneto signal and condition it into
a clean tach output. Mounting the tach adapter close to the magneto will prevent you from making a
magneto antenna and reduce the amount of problems a magneto can cause to a data logger.
We also recommend changing your mag kill switch from a “lightning wire” kill switch to a conditioned
relay kill switch. When using a hot wire kill switch you are running the full load of your ignition
system up to the cockpit to the switch and then all the way back to the magneto. This creates a magneto
antenna that significantly expands your ignition noise radius. By using a clean 12V or ground signal to
trigger a relay that will cut the magneto off, you successfully keep all of your ignition noise centered
around the engine.
WARNING:
Connecting the magneto directly to the DataMaxx will result in a failure and void
your warranty.
Copyright c 2008 Computech Systems Inc. 17