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Bob Ashlock Bob Ashlock is online now
Join Date: Nov 2007
Location: Fullerton, California
Posts: 360
Tachometer Adapter

I’m going to do a little self-promoting here and hope I don’t get my hand slapped for trying to “go commercial” here on the forum. From time to time the topic of adapting tachometers to work with different engines (without sending them out to be torn open and “re-calibrated”) has come up. In my case where I installed a 911 engine in my 912, I wanted to use my existing 4-cylinder tachometer because it was in good shape and had a custom white face that matched my other gauges. Problem is that it was reading 1.5 x faster due to the two extra pulses/cylinders. Since this was a “one-off” situation, I kluged-together a little external analog circuit to change the pulse rate to the tach and went on with other adventures. Over time, I've engaged in discussions with various forum members about how I did this and that got me inspired to further improve the design to be more "universal". My new design is easy to install and can be used with any combination of engine size (4, 6 or 8 cylinders) and tach design (4, 6 or 8 cylinder). It is intended to work with Kettering (points) ignitions, or with electronic (Pertronix) and CDI units. It may also be useful for solving "tach-bounce" and related mis-match problems as it provides a selectable "regenerated" low-voltage or high-voltage drive pulse to the tach.

All that to say that I now have a prototype of this new adapter running in my car and am trying to determine if there is enough interest out there to move forward with producing and offering some units.
Old 09-03-2011, 10:34 AM
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