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(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 later. In this case, you simply need to try the other terminal. Note also that some ignition systems require use of the “+” side.

Internal coil magneto ignitions

Internal coil magneto ignitions have a “kill” wire or terminal wire coming from the magneto main unit. This wire is typically connected to the coil inside the magneto main unit and thus provides a suitable RPM signal to connect to.

External coil magneto ignition systems

Most external coil magneto ignition systems simply don’t want to provide a clean RPM signal without the use of a RPM converter/interface. Consult with Computech to determine your specific needs.

All ignitions

TESTING: Before testing your RPM connection, be sure your DATAPRO-45™ is properly calibrated for your engine. If it’s not, no harm will come; the RPM indication will be wrong, however. Your DATAPRO-45™ comes from the factory calibrated for an 8 cylinder, 4 stroke motor. If you have anything else, you’ll need to use the DATAPRO ON-LINEsoftware to calibrate your main unit to match your specific requirements.

Now, test your RPM connection by starting the engine and letting it idle. The LCD display should indicate the correct RPM. You should be concerned with a having a “smooth” reading. In spite of how smooth you may believe your idle to be, it will probably bounce very rapidly within a 25 to 100 RPM range. While the last two digits may seen to vary wildly, your reading is probably just fine as long as the remaining digits to the left appear steady.

If you think you have a RPM problem, then see the troubleshooting section. Note that many race ignition systems generate a great deal of radio frequency interference. This interference can cause erratic RPM readings and may sometimes even cause computer systems such as your DATAPRO-45™ to go totally “haywire”. If your LCD seems to go “haywire” as soon as you start the engine, or if you can’t seem to get a smooth RPM display no matter what you do, then you may need to go a couple of steps further. Aside from checking the troubleshooting section, make sure that all wires are as far from any ignition

Copyright 1999 Computech Systems Inc


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