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Originally Posted by HellsDrifter 666
Your getting the tach signal from the dash wiring and the signal is not much different between the two so I assume it will work on both E and DE signal. My car was a E originally so all my wiring is single cam dash wiring. It should work.
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If that was the case, then why doesn't SOHC tachs work with DOHC or SR motors? The interior harness is identical to both SOHC and DOHC. The signal however, is different. Do you think the signal is generated in the wiring? Something is sending the signal through the wires to the tach.. (duh). To my understanding, the signal comes from the CAS at the base of the distributor (i think).
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The tach signal doesn't originate from the CAS. It comes from the collector of the power transistor for the coil. In the E the signal goes straight to the tach but on the DE the signal goes through the ECU for some signal processing. The simple solution is to get a DE tach and swap it in the gague cluster. You even have the correct redline then.
If you can't get a DE tach then you could try putting a scope on the tach signal coming from the ECU and see if it is 0-5V or 0-12V. I _think_ the E signal is 0-12V and the DE is 0-5V, but I could easily be wrong. If I'm not mistaken (ha ha) then you could build a buffer circuit to translate the levels from 0-5V to 0-12V and see if that works. If I'm wrong then it would probably fry your E tach, so be warned.
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