MSD tach adapter 8920

[madkaw]

It's almost funny that I can wire up a Megasquirt stand alone ECU, but

I can't seem to get the wiring on the tach adapter to work. I think it's

the path of those dam tach wires. The black/white changes to green/white and then back to black white-argh.

I finally pulled the tach out and got out my multimeter and tracked the

wires, since there are several wires with this color combo. I found where

the wires come out under the glove box in separate plugs -of all things.

So I run a continuity test at these two ends under the glove box and

they are connected. The problem seems to be that the ignition is in this

loop somehow, but still trying to figure that out.

The Megasquirt has a tach out wire. I tried powering the black/white

wire and it was causing the starter to try and turn over in acc.

position. I can't read the schematic with regards to what wires are tied

together at the different ignition switch-positions.

Any help from someone who did a MSD igniton with a current tach

http://www.msdignition.com/Products/Accessories/Tach_Adapters/8920_-_Tach_Adapter,_Magnetic_Trigger.aspx

[Chickenman]

 What's your ignition setup with the Megasquirt? Still have a dizzy or have you gone direct fire? 

[Chickenman]

This may help if you are using the 280ZX Turbo Dizzy. Note the reference to different Tachs in the early models. I do recall that the early Tachs are wired differently and operate differently than the later style.

 

Quote

COIL wiring in the 240z
Like I said, I used the stock 280zxt coil. The schematics only show how to connect MSnS and the HEI module, but doesn't show all of the existing wiring in the car. My Turbo coil is wired as follows:

Black White (BW) wire connected to coil +
HEI module connected to coil + (as in the schematic)
coil + is connected to a condenser
condenser black wire then connects to the base of the distributor
coil - is only conected to the HEI module as in the schematic

The BW wire provides 12 volts to the coil when the ignition switch is turned on. The 240z originally had a ballast resistor to drop the voltage to the coil, I removed that so the turbo coil really gets 12 volts. Also, my Tachometer works with this setup, but I do have a 73 240z which rumor says that the 73 tach is different than earlier 240z tachs.
 

http://forums.hybridz.org/topic/23244-megasquirtnspark-mssmsns-installation-guide/

 

[madkaw]

Using COP set up, no dizzy . Voltage type tachs  seem to be easier since no need for an adapter. I guess I will just wire directly off 5he back of the tach to bypass any possible wire detours. Might consider a newer 280z tach retro fitted .

[Chickenman]

Yeah.. I don't think you can trigger an early Tach using COP even with an MSD Adapter. The early Tachs are a current driven type like early Smith or Veglia Gauges. It's a totally different type of Tach circuitry than the later Electronic ones.

I did find a site where you can build a PC circuit board to convert Current driven Tachs to Electronic Tachs that accept standard square wave signals. And he has made this work for early Datsun 240Z Tachs.

Really good article!! Helps with wiring aftermarket Tachs with COP as well. Or with MSD/Crane/Haltech/Megasquirt and Dizzy as well:

http://forums.hybridz.org/topic/86982-converting-a-current-driven-tacho-into-an-electronic-tacho/

http://www.dinoplex.org/tachoconversion/

 

With an Electronic Tach ( 260Z/280Z or aftermarket ) you should be able to trigger off the Tach signal output from the MegaSquirt.

 

 

 

Edited January 5, 2016 by Chickenman