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Making the original cluster Tacho work with Megasquirt
#2
(05-28-2013, 01:35 AM)Turbo_tracker Wrote: Hello to all and thanks for creating this forum and fixkick info!!! its been a ton of help on my Geo tracker Big Grin

Well my question is as follows:

I've owned a 91 yellow geo tracker since '05, kept it stock til last year when I went full on on modifying it with dual transfer cases (kicker3), 10" lift long arm suspension, 85 toyota axles and 33" mud tires after all that the little engine wasnt able to go at highway speeds (max 60 mph to the floor) so I decided a little radical mod and installed a K03 turbo on it, As I read it on different sites the stock ecu and fuel injection components werent up to the task so I had to buy and assemble a standalone ECU from Mega squirt (MS) and modified the engine intake manifold to be MPI instead of TBI (made a 2" adapter out of aluminum and machined ports on it to install 1 inj per cyl)
Wow , and MPI 8v, cool. ! I did a 8v TBI with megasquirt.

Ok, so now Im running the spark and fuel from the MS, the stock dash has the speedo, fuel gauge, charging lamp, high beam, 4wd and turn signals working also installed an AFR gauge, a mechanical oil pressure gauge, boost vacuum gauge and engine temp gauge, but the Tacho on the stock cluster is not working...
it needs only and input from the minus side of the coil. but in your case, you have custom ignition right.
show me the schematic of you custom ignition,
on my web site i have the stock scope readings.
here.
http://www.fixkick.com/look/ECU-secrets/tacho.jpg
we can mimic that easy.
are you running CDI or MSD , it will blow the tacho up, if driven from 500vdc CDI systems, ask how to cur that.
if running MSD, they have and adaptor that allows that, on mine, the MSD has a tacho drive. (ask how to make it work with suz.)






On the MS site it explains 3 different ways to wire for the tacho signal: Does anyone can recommend me which way to try and wire the tacho?
there are like 10 ignitions systems you can run,
but, coil points, stock, MDS, CDI, or simple transistor drive (same as suz) or coil packs, cops, dual coil packs, , wasted spark, GM spare, ford, Chrysler. etc.


here's a link to those instructions

http://www.msextra.com/doc/ms1extra/MS_E...m#tachoout
the mS option that matches best is the coil option, they are just using any relay 12v only , to mimic a Induction primary to get the
50vdc EMF back kick as seen in my Jpg above.


Also I removed all the stock wiring regarding engine sensors, ECU, radio, etc that were not needed anymore to make the new wiring look easier...

its been quite a mess for the last 13 months but at least its coming along Smile

Here's a pic of my Tracker

Thanks for your time and help!!
first off, thanks for sharing ! nice project, sounds like fun.

I have never reversed engineered the tacho.(i should have..) but It has 3 wires (gnd,12v and sig) and does trigger off the back EMF signal of the stock coil.
im not sure of the stock tacho is sensitive to duty cycle of the pulse. (many are) i suspect it is.

in a good tach its digital and only measures rep, rates but that is not common, in factory cheap tacho's.

what Ignition system are you running, that dictates solution.

cheers !
http://www.fixkick.com
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RE: Making the original cluster Tacho work with Megasquirt - by fixkick - 05-28-2013, 11:40 PM

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