Tach problems, 6 conversion Options

[GulleyGulley]

Installed a 86 3.2 into my car with a tach from the donor. Everything works but the tach. It reads about double what it should. Any ideas why it's off?

[timothy_nd28]

Your not the only one with this issue, this is why I'm designing a drop in circuit board that is universal for all Porsche tachs up to the early 80's. Your issue could be with the dwell setting, CDI box, or even the tach. VDO did a wonderful job designing their tach's with what they had to work with back in the day. They had mechanical spring/mass systems with little dampening. The tach signal has a lots of ringing to deal with. This is where modern technology comes in play. There is a time where trying to fix an old problem just doesn't make much sense, where upgrading with newer technology while keeping the original look makes better sense.


My new design is a better circuit which will accept all signals strong or weak. Using a solid state design to reshape the input wave form, and ultimately drive an air core frictionless movement. I'm even entertaining the idea of installing memory on this circuit board for high rpm play back. Just trying to figure out how to do this without installing a button somewhere.

This new design will have jumper settings for 7k tachs up to 12k along with different cylinder engines for each range. The circuit board will be the same diameter as the inside of the gauge can. The outer circumference will have a halo of LED lights, and my custom RGB controller already built onto the same board. A truly universal drop in replacement that kills 2 birds with one stone!


Sorry for the thread highjack