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Tachometer Resistance Adjustment 88 Fiero 3800 Series II by aarwigg
Started on: 04-26-2014 05:37 PM
Replies: 3 (214 views)
Last post by: aarwigg on 04-27-2014 08:55 PM
aarwigg
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Report this Post04-26-2014 05:37 PM Click Here to See the Profile for aarwiggSend a Private Message to aarwiggEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was searching for the way to adjust my 3800 series II in an 88 fiero and I saw where people had said to add resistance to the tach signal, but I never saw how much. I'm just posting this to help out people in the future. I compared the tach to the OBD scan tool I have, and they were very close, almost perfect, with 13,760 ohms, or 13.76k ohms.

UPDATE: Well, after driving for a while, the resistors heated up, and obviously that increased the resistance so the tach was reading lower than OBD. I will update later with the value that holds true after the engine has warmed up. It looks like it will read high when cold, but this will work for a simple, cheap fix.

[This message has been edited by aarwigg (edited 04-26-2014).]

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Fieroking
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Report this Post04-26-2014 08:20 PM Click Here to See the Profile for FierokingClick Here to visit Fieroking's HomePageClick Here to Email FierokingSend a Private Message to FierokingEdit/Delete MessageReply w/QuoteDirect Link to This Post
Dakota Digital has a new interface that reads ODB II data for both the tach and speedo.

Joe Sokol

------------------
85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)
www.fieroking.com

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phonedawgz
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Report this Post04-26-2014 08:31 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
The tach signal is sent as digital pulses, not a voltage or resistance. You can't 'trim' the tach reading by adding a resistor to the tach signal. The resistor that is used to adjust the tach in the other posts is an resistor inside the tach itself. It should not need an adjustment when going from a 2.8 six to a 3800 six.

http://www.fieros.de/en/articles/tach.html

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aarwigg
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Report this Post04-27-2014 08:55 PM Click Here to See the Profile for aarwiggSend a Private Message to aarwiggEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the info. Now I am wondering how I achieved results?
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