Quote:
Originally Posted by Wonderboy
IT LIVES! (other words Will said)
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Don't you have a bicycle computer laying around? You could put the magnet on a rotating part of the engine and do the math to count back to RPMs that way... Lots of work, but it should work, ideally.
On the other hand, it's probably just as easy to get a general idea of engine speed by hooking up the CRX's green wire (at the dizzy) to the ignition (-) on the coil of the Metro engine. (I'm relatively sure that will work, anyway.)
Usually, aftermarket tachometers are driven by the negative side of the coil. They get a signal based on the number of times the coil is switched per interval of time. I think the CRX's tach works the same, but can't be sure about it. It's connected to the ignitor module, which works similarly to contact points in the points and condenser ignition system, only instead of being operated by an eccentric lobe, it's operated by the ECM/ECU/PCM/Whatever you want to call it.
My other stupid idea at one point was just to drill/tap a hole into the approximate center of the crank pulley bolt, and attach a tach from a motorcycle which was driven by a cable. Not sure how that would have worked out, though, since I never actually did it.